write an article on climate change

ENCYCLOPEDIC ENTRY

Climate change.

Climate change is a long-term shift in global or regional climate patterns. Often climate change refers specifically to the rise in global temperatures from the mid-20th century to present.

Earth Science, Climatology

Fracking tower

Fracking is a controversial form of drilling that uses high-pressure liquid to create cracks in underground shale to extract natural gas and petroleum. Carbon emissions from fossils fuels like these have been linked to global warming and climate change.

Photograph by Mark Thiessen / National Geographic

Climate is sometimes mistaken for weather. But climate is different from weather because it is measured over a long period of time, whereas weather can change from day to day, or from year to year. The climate of an area includes seasonal temperature and rainfall averages, and wind patterns. Different places have different climates. A desert, for example, is referred to as an arid climate because little water falls, as rain or snow, during the year. Other types of climate include tropical climates, which are hot and humid , and temperate climates, which have warm summers and cooler winters.

Climate change is the long-term alteration of temperature and typical weather patterns in a place. Climate change could refer to a particular location or the planet as a whole. Climate change may cause weather patterns to be less predictable. These unexpected weather patterns can make it difficult to maintain and grow crops in regions that rely on farming because expected temperature and rainfall levels can no longer be relied on. Climate change has also been connected with other damaging weather events such as more frequent and more intense hurricanes, floods, downpours, and winter storms.

In polar regions, the warming global temperatures associated with climate change have meant ice sheets and glaciers are melting at an accelerated rate from season to season. This contributes to sea levels rising in different regions of the planet. Together with expanding ocean waters due to rising temperatures, the resulting rise in sea level has begun to damage coastlines as a result of increased flooding and erosion.

The cause of current climate change is largely human activity, like burning fossil fuels , like natural gas, oil, and coal. Burning these materials releases what are called greenhouse gases into Earth’s atmosphere . There, these gases trap heat from the sun’s rays inside the atmosphere causing Earth’s average temperature to rise. This rise in the planet's temperature is called global warming. The warming of the planet impacts local and regional climates. Throughout Earth's history, climate has continually changed. When occuring naturally, this is a slow process that has taken place over hundreds and thousands of years. The human influenced climate change that is happening now is occuring at a much faster rate.

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• ENVIRONMENT

How global warming is disrupting life on Earth

The signs of global warming are everywhere, and are more complex than just climbing temperatures.

Our planet is getting hotter. Since the Industrial Revolution—an event that spurred the use of fossil fuels in everything from power plants to transportation—Earth has warmed by 1 degree Celsius, about 2 degrees Fahrenheit.  

That may sound insignificant, but 2023 was the hottest year on record , and all 10 of the hottest years on record have occurred in the past decade.  

Global warming and climate change are often used interchangeably as synonyms, but scientists prefer to use “climate change” when describing the complex shifts now affecting our planet’s weather and climate systems.  

Climate change encompasses not only rising average temperatures but also natural disasters, shifting wildlife habitats, rising seas , and a range of other impacts. All of these changes are emerging as humans continue to add heat-trapping greenhouse gases , like carbon dioxide and methane, to the atmosphere.

What causes global warming?

When fossil fuel emissions are pumped into the atmosphere, they change the chemistry of our atmosphere, allowing sunlight to reach the Earth but preventing heat from being released into space. This keeps Earth warm, like a greenhouse, and this warming is known as the greenhouse effect .  

Carbon dioxide is the most commonly found greenhouse gas and about 75 percent of all the climate warming pollution in the atmosphere. This gas is a product of producing and burning oil, gas, and coal. About a quarter of Carbon dioxide also results from land cleared for timber or agriculture.  

Methane is another common greenhouse gas. Although it makes up only about 16 percent of emissions, it's roughly 25 times more potent than carbon dioxide and dissipates more quickly. That means methane can cause a large spark in warming, but ending methane pollution can also quickly limit the amount of atmospheric warming. Sources of this gas include agriculture (mostly livestock), leaks from oil and gas production, and waste from landfills.  

What are the effects of global warming?  

One of the most concerning impacts of global warming is the effect warmer temperatures will have on Earth's polar regions and mountain glaciers. The Arctic is warming four times faster than the rest of the planet. This warming reduces critical ice habitat and it disrupts the flow of the jet stream, creating more unpredictable weather patterns around the globe.  

( Learn more about the jet stream. )

A warmer planet doesn't just raise temperatures. Precipitation is becoming more extreme as the planet heats. For every degree your thermometer rises, the air holds about seven percent more moisture. This increase in moisture in the atmosphere can produce flash floods, more destructive hurricanes, and even paradoxically, stronger snow storms.  

The world's leading scientists regularly gather to review the latest research on how the planet is changing. The results of this review is synthesized in regularly published reports known as the Intergovernmental Panel on Climate Change (IPCC) reports.  

A recent report outlines how disruptive a global rise in temperature can be:

• Coral reefs are now a highly endangered ecosystem. When corals face environmental stress, such as high heat, they expel their colorful algae and turn a ghostly white, an effect known as coral bleaching . In this weakened state, they more easily die.  
• Trees are increasingly dying from drought , and this mass mortality is reshaping forest ecosystems.
• Rising temperatures and changing precipitation patterns are making wildfires more common and more widespread. Research shows they're even moving into the eastern U.S. where fires have historically been less common.
• Hurricanes are growing more destructive and dumping more rain, an effect that will result in more damage. Some scientists say we even need to be preparing for Cat 6 storms . (The current ranking system ends at Cat 5.)

How can we limit global warming?  

Limiting the rising in global warming is theoretically achievable, but politically, socially, and economically difficult.  

Those same sources of greenhouse gas emissions must be limited to reduce warming. For example, oil and gas used to generate electricity or power industrial manufacturing will need to be replaced by net zero emission technology like wind and solar power. Transportation, another major source of emissions, will need to integrate more electric vehicles, public transportation, and innovative urban design, such as safe bike lanes and walkable cities.  

( Learn more about solutions to limit global warming. )

One global warming solution that was once considered far fetched is now being taken more seriously: geoengineering. This type of technology relies on manipulating the Earth's atmosphere to physically block the warming rays of the sun or by sucking carbon dioxide straight out of the sky.

Restoring nature may also help limit warming. Trees, oceans, wetlands, and other ecosystems help absorb excess carbon—but when they're lost, so too is their potential to fight climate change.  

Ultimately, we'll need to adapt to warming temperatures, building homes to withstand sea level rise for example, or more efficiently cooling homes during heat waves.  

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• CLIMATE CHANGE
• ENVIRONMENT AND CONSERVATION
• POLAR REGIONS

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Science News

Abdulhamid Hosbas/Anadolu Agency via Getty Images

Century of Science: Theme

Our climate change crisis

The climate change emergency.

Even in a world increasingly battered by weather extremes, the summer 2021 heat wave in the Pacific Northwest stood out. For several days in late June, cities such as Vancouver, Portland and Seattle baked in record temperatures that killed hundreds of people. On June 29 Lytton, a village in British Columbia, set an all-time heat record for Canada, at 121° Fahrenheit (49.6° Celsius); the next day, the village was incinerated by a wildfire.

Within a week, an international group of scientists had analyzed this extreme heat and concluded it would have been virtually impossible without climate change caused by humans. The planet’s average surface temperature has risen by at least 1.1 degree Celsius since preindustrial levels of 1850–1900 — because people are loading the atmosphere with heat-trapping gases produced during the burning of fossil fuels, such as coal and gas, and from cutting down forests.

A little over 1 degree of warming may not sound like a lot. But it has already been enough to fundamentally transform how energy flows around the planet. The pace of change is accelerating, and the consequences are everywhere. Ice sheets in Greenland and Antarctica are melting, raising sea levels and flooding low-lying island nations and coastal cities. Drought is parching farmlands and the rivers that feed them. Wildfires are raging. Rains are becoming more intense, and weather patterns are shifting .

The roots of understanding this climate emergency trace back more than a century and a half. But it wasn’t until the 1950s that scientists began the detailed measurements of atmospheric carbon dioxide that would prove how much carbon is pouring from human activities. Beginning in the 1960s, researchers began developing comprehensive computer models that now illuminate the severity of the changes ahead.

Global average temperature change, 1850–2021

Long-term climate datasets show that Earth’s average surface temperature (combined land and ocean) has increased by more than 1 degree Celsius since preindustrial times. Temperature change is the difference from the 1850–1900 average.

Today we know that climate change and its consequences are real, and we are responsible. The emissions that people have been putting into the air for centuries — the emissions that made long-distance travel, economic growth and our material lives possible — have put us squarely on a warming trajectory . Only drastic cuts in carbon emissions, backed by collective global will, can make a significant difference.

“What’s happening to the planet is not routine,” says Ralph Keeling, a geochemist at the Scripps Institution of Oceanography in La Jolla, Calif. “We’re in a planetary crisis.” — Alexandra Witze

Tracking a Greenland glacier

The calving front of Greenland’s Helheim Glacier, which flows toward the sea where it crumbles into icebergs, held roughly the same position from the 1970s until 2001 (left, the calving front is to the far right of the image). But by 2005 (right), it had retreated 7.5 kilometers toward its source. 

The first climate scientists

One day in the 1850s, Eunice Newton Foote, an amateur scientist and women’s rights activist living in upstate New York, put two glass jars in sunlight. One contained regular air — a mix of nitrogen, oxygen and other gases including carbon dioxide — while the other contained just CO 2 . Both had thermometers in them. As the sun’s rays beat down, Foote observed that the jar of CO 2 alone heated more quickly, and was slower to cool, than the one containing plain air.

The results prompted Foote to muse on the relationship between CO 2 , the planet and heat. “An atmosphere of that gas would give to our earth a high temperature,” she wrote in an 1856 paper summarizing her findings .

Three years later, working independently and apparently unaware of Foote’s discovery, Irish physicist John Tyndall showed the same basic idea in more detail. With a set of pipes and devices to study the transmission of heat, he found that CO 2 gas, as well as water vapor, absorbed more heat than air alone. He argued that such gases would trap heat in Earth’s atmosphere, much as panes of glass trap heat in a greenhouse, and thus modulate climate. “As a dam built across a river causes a local deepening of the stream, so our atmosphere, thrown as a barrier across the terrestrial rays, produces a local heightening of the temperature at the Earth’s surface,” he wrote in 1862.

Today Tyndall is widely credited with the discovery of how what are now called greenhouse gases heat the planet, earning him a prominent place in the history of climate science. Foote faded into relative obscurity — partly because of her gender, partly because her measurements were less sensitive. Yet their findings helped kick off broader scientific exploration of how the composition of gases in Earth’s atmosphere affects global temperatures.

Carbon floods in

Humans began substantially affecting the atmosphere around the turn of the 19th century, when the Industrial Revolution took off in Britain. Factories burned tons of coal; fueled by fossil fuels, the steam engine revolutionized transportation and other industries. In the decades since, fossil fuels including oil and natural gas have been harnessed to drive a global economy. All these activities belch gases into the air.

Yet Svante Arrhenius, a Swedish physical chemist, wasn’t worried about the Industrial Revolution when he began thinking in the late 1800s about changes in atmospheric CO 2 levels. He was instead curious about ice ages — including whether a decrease in volcanic eruptions, which can put CO 2 into the atmosphere, would lead to a future ice age. Bored and lonely in the wake of a divorce, Arrhenius set himself to months of laborious calculations involving moisture and heat transport in the atmosphere at different zones of latitude. In 1896 he reported that halving the amount of CO 2 in the atmosphere could indeed bring about an ice age — and that doubling CO 2 would raise global temperatures by around 5 to 6 degrees C.

It was a remarkably prescient finding for work that, out of necessity, had simplified Earth’s complex climate system down to just a few variables. Today, estimates for how much the planet will warm through a doubling of CO 2 — a measure known as climate sensitivity — range between 1.5 degrees and 4.5 degrees Celsius. (The range remains broad in part because scientists now incorporate their understanding of many more planetary feedbacks than were recognized in Arrhenius’ day.)  

But Arrhenius’ findings didn’t gain much traction with other scientists at the time. The climate system seemed too large, complex and inert to change in any meaningful way on a timescale that would be relevant to human society. Geologic evidence showed, for instance, that ice ages took thousands of years to start and end. What was there to worry about? And other laboratory experiments — later shown to be flawed — appeared to indicate that changing levels of CO 2 would have little impact on heat absorption in the atmosphere. Most scientists aware of the work came to believe that Arrhenius had been proved wrong.

One researcher, though, thought the idea was worth pursuing. Guy Stewart Callendar, a British engineer and amateur meteorologist, had tallied weather records over time, obsessively enough to determine that average temperatures were increasing at 147 weather stations around the globe. In 1938, in a paper in a Royal Meteorological Society journal , he linked this temperature rise to the burning of fossil fuels. Callendar estimated that fossil fuel burning had put around 150 billion metric tons of CO 2 into the atmosphere since the late 19th century.

Like many of his day, Callendar didn’t see global warming as a problem. Extra CO 2 would surely stimulate plants to grow and allow crops to be farmed in new regions. “In any case the return of the deadly glaciers should be delayed indefinitely,” he wrote. But his work revived discussions tracing back to Tyndall and Arrhenius about how the planetary system responds to changing levels of gases in the atmosphere. And it began steering the conversation toward how human activities might drive those changes.

When World War II broke out the following year, the global conflict redrew the landscape for scientific research. Hugely important wartime technologies, such as radar and the atomic bomb, set the stage for “big science” studies that brought nations together to tackle high-stakes questions of global reach. And that allowed modern climate science to emerge.

The Keeling curve and climate change

One major postwar effort was the International Geophysical Year, an 18-month push in 1957–1958 that involved a wide array of scientific field campaigns including exploration in the Arctic and Antarctica. Climate change wasn’t a high research priority during the IGY, but some scientists in California, led by Roger Revelle of the Scripps Institution of Oceanography in La Jolla, used the funding influx to begin a project they’d long wanted to do. The goal was to measure CO 2 levels at different locations around the world, accurately and consistently.

The job fell to geochemist Charles David Keeling, who put ultraprecise CO 2 monitors in Antarctica and on the Hawaiian volcano of Mauna Loa. Funds soon ran out to maintain the Antarctic record, but the Mauna Loa measurements continued. Thus was born one of the most iconic datasets in all of science — the “Keeling curve,” which tracks the rise of atmospheric CO 2 . When Keeling began his measurements in 1958, CO 2 made up 315 parts per million of the global atmosphere. Within just a few years it became clear that the number was increasing year by year. Because plants take up CO 2 as they grow in spring and summer and release it as they decompose in fall and winter, CO 2 concentrations rose and fell each year in a sawtooth pattern — but superimposed on that pattern was a steady march upward.  

Monthly average CO 2 concentrations at Mauna Loa Observatory

Atmospheric carbon dioxide measurements collected continuously since 1958 at Mauna Loa volcano in Hawaii show the rise due to human activities. The visible sawtooth pattern is due to seasonal plant growth: Plants take up CO 2 in the growing seasons, then release it as they decompose in fall and winter.

“The graph got flashed all over the place — it was just such a striking image,” says Ralph Keeling, who is Charles David Keeling’s son. Over the years, as the curve marched higher, “it had a really important role historically in waking people up to the problem of climate change.” The Keeling curve has been featured in countless earth science textbooks, congressional hearings and in Al Gore’s 2006 documentary on climate change, An Inconvenient Truth . Each year the curve keeps going up: In 2016 it passed 400 ppm of CO 2 in the atmosphere, as measured during its typical annual minimum in September. In 2021, the annual minimum was 413 ppm. (Before the Industrial Revolution, CO 2 levels in the atmosphere had been stable for centuries at around 280 ppm.)

Around the time that Keeling’s measurements were kicking off, Revelle also helped develop an important argument that the CO 2 from human activities was building up in Earth’s atmosphere. In 1957 he and Hans Suess, also at Scripps at the time, published a paper that traced the flow of radioactive carbon through the oceans and the atmosphere. They showed that the oceans were not capable of taking up as much CO 2 as previously thought; the implication was that much of the gas must be going into the atmosphere instead. “Human beings are now carrying out a large-scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future,” Revelle and Suess wrote in the paper. It’s one of the most famous sentences in earth science history.

“Human beings are now carrying out a large-scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future.”

Here was the insight underlying modern climate science: Atmosheric CO 2 is increasing, and humans are causing the buildup. Revelle and Suess became the final piece in a puzzle dating back to Svante Arrhenius and John Tyndall.

“I tell my students that to understand the basics of climate change, you need to have the cutting-edge science of the 1860s, the cutting-edge math of the 1890s and the cutting-edge chemistry of the 1950s,” says Joshua Howe, an environmental historian at Reed College in Portland, Ore.

Environmental awareness grows

As this scientific picture began to emerge in the late 1950s, Science News was on the story. A March 1, 1958 article in Science News Letter , “Weather May Be Warming,” described a warm winter month in the Northern Hemisphere. It posits three theories, including that “carbon dioxide poured into the atmosphere by a booming industrial civilization could have caused the increase. By burning up about 100 billion tons of coal and oil since 1900, man himself may be changing the climate.” By 1972, the magazine was reporting on efforts to expand global atmospheric greenhouse gas monitoring beyond Keeling’s work; two years later, the U.S. National Oceanic and Atmospheric Administration launched its own CO 2 monitoring network, now the biggest in the world.

Environmental awareness on other issues grew in the 1960s and 1970s. Rachel Carson catalyzed the modern U.S. environmental movement in 1962 when she published a magazine series and then a book, Silent Spring , condemning the pesticide DDT for its ecological impacts. 1970 saw the celebration of the first Earth Day , in the United States and elsewhere, and in India in 1973 a group of women led a series of widely publicized protests against deforestation. This Chipko movement explicitly linked environmental protection with protecting human communities, and helped seed other environmental movements.

The fragility of global energy supplies was also becoming more obvious through the 1970s. The United States, heavily dependent on other countries for oil imports, entered a gas shortage in 1973–74 when Arab members of the Organization of the Petroleum Exporting Countries cut off oil supplies because of U.S. government support for Israel. The shortage prompted more people to think about the finiteness of natural resources and the possibility of overtaxing the planet. — Alexandra Witze

Climate change evidence piles up

Observational data collected throughout the second half of the 20th century helped researchers gradually build their understanding of how human activities were transforming the planet. “It was a sort of slow accretion of evidence and concern,” says historian Joshua Howe of Reed College.

Environmental records from the past, such as tree rings and ice cores, established that the current changes in climate are unusual compared with the recent past. Yet such paleoclimatology data also showed that climate has changed quickly in the deep past — driven by triggers other than human activity, but with lessons for how abrupt planetary transformations can be.

Ice cores pulled from ice sheets, such as that atop Greenland, offer some of the most telling insights for understanding past climate change. Each year snow falls atop the ice and compresses into a fresh layer of ice representing climate conditions at the time it formed. The abundance of certain forms, or isotopes, of oxygen and hydrogen in the ice allows scientists to calculate the temperature at which it formed, and air bubbles trapped within the ice reveal how much carbon dioxide and other greenhouse gases were in the atmosphere at that time. So drilling down into an ice sheet is like reading the pages of a history book that go back in time the deeper you go.

Scientists began reading these pages in the early 1960s, using ice cores drilled at a U.S. military base in northwest Greenland . Contrary to expectations that past climates were stable, the cores hinted that abrupt climate shifts had happened over the last 100,000 years. By 1979, an international group of researchers was pulling another deep ice core from a second location in Greenland — and it, too, showed that abrupt climate change had occurred in the past. In the late 1980s and early 1990s a pair of European- and U.S.-led drilling projects retrieved even deeper cores from near the top of the ice sheet, pushing the record of past temperatures back a quarter of a million years.

Together with other sources of information, such as sediment cores drilled from the seafloor and molecules preserved in ancient rocks, the ice cores allowed scientists to reconstruct past temperature changes in extraordinary detail. Many of those changes happened alarmingly fast. For instance, the climate in Greenland warmed abruptly more than 20 times in the last 80,000 years, with the changes occurring in a matter of decades. More recently, a cold spell that set in around 13,000 years ago suddenly came to an end around 11,500 years ago — and temperatures in Greenland rose 10 degrees Celsius in a decade.

Evidence for such dramatic climate shifts laid to rest any lingering ideas that global climate change would be slow and unlikely to occur on a timescale that humans should worry about. “It’s an important reminder of how ‘tippy’ things can be,” says Jessica Tierney, a paleoclimatologist at the University of Arizona in Tucson.

More evidence of global change came from Earth-observing satellites, which brought a new planet-wide perspective on global warming beginning in the 1960s. From their viewpoint in the sky, satellites have measured the steady rise in global sea level — currently 3.4 millimeters per year and accelerating, as warming water expands and as ice sheets melt — as well as the rapid decline in ice left floating on the Arctic Ocean each summer at the end of the melt season. Gravity-sensing satellites have ‘weighed’ the Antarctic and Greenlandic ice sheets from above since 2002, reporting that more than 400 billion metric tons of ice are lost each year.

Temperature observations taken at weather stations around the world also confirm that we are living in the hottest years on record. The 10 warmest years since record keeping began in 1880 have all occurred since 2005. And nine of those 10 have come since 2010.

What’s more, extreme weather is hammering the planet more and more frequently. That 2021 heat wave in the Pacific Northwest, for instance, is just a harbinger of what’s to come. — Alexandra Witze

Worrisome predictions from climate models

By the 1960s, there was no denying that the planet was warming. But understanding the consequences of those changes — including the threat to human health and well-being — would require more than observational data. Looking to the future depended on computer simulations: complex calculations of how energy flows through the planetary system. Such models of the climate system have been crucial to developing projections for what we can expect from greenhouse warming.

A first step in building climate models was to connect everyday observations of weather to the concept of forecasting future climate. During World War I, the British mathematician Lewis Fry Richardson imagined tens of thousands of meteorologists working to forecast the weather, each calculating conditions for a small part of the atmosphere but collectively piecing together a global forecast. Richardson published his work in 1922, to reviews that called the idea “of almost quixotic boldness.”

But it wasn’t until after World War II that computational power turned Richardson’s dream into reality. In the wake of the Allied victory, which relied on accurate weather forecasts for everything from planning D-Day to figuring out when and where to drop the atomic bombs, leading U.S. mathematicians acquired funding from the federal government to improve predictions. In 1950 a team led by Jule Charney, a meteorologist at the Institute for Advanced Study in Princeton, N.J., used the ENIAC, the first general-purpose, programmable electronic computer, to produce the first computer-driven regional weather forecast . The forecasting was slow and rudimentary, but it built on Richardson’s ideas of dividing the atmosphere into squares, or cells, and computing the weather for each of those. With the obscure title “Numerical integration of the barotropic vorticity equation,” the paper reporting the results set the stage for decades of climate modeling to follow.

By 1956 Norman Phillips, a member of Charney’s team, had produced the world’s first general circulation model, which captured how energy flows between the oceans, atmosphere and land. Phillips ran the calculations on a computer with just 5 kilobytes of memory, yet it was able to reproduce monthly and seasonal patterns in the lower atmosphere. That meant scientists could begin developing more realistic models of how the planet responds to factors such as increasing levels of greenhouse gases. The field of climate modeling was born.

The work was basic at first, because early computers simply didn’t have much computational power to simulate all aspects of the planetary system. “People thought that it was stupid to try to study this greenhouse-warming issue by three-dimensional model[s], because it cost so much computer time,” meteorologist Syukuro Manabe told physics historian Spencer Weart in a 1989 oral history .

Climate models have predicted how much ice the Ilulissat region of the Greenland ice sheet might lose by 2300 based on different scenarios for greenhouse gas emissions. The models are compared to 2008 (first image). In a best-case scenario, in which emissions peak by mid-century, the speed at which the glacier is sending ice out into the ocean is much lower (second image) than with a worst-case scenario, in which emissions rise at a high rate (third image).

An important breakthrough came in 1967, when Manabe and Richard Wetherald — both at the Geophysical Fluid Dynamics Laboratory in Princeton, a lab born from Charney’s group — published a paper in the Journal of the Atmospheric Sciences that modeled connections between Earth’s surface and atmosphere and calculated how changes in carbon dioxide would affect the planet’s temperature. Manabe and Wetherald were the first to build a computer model that captured the relevant processes that drive climate , and to accurately simulate how the Earth responds to those processes. (Manabe shared the 2021 Nobel Prize in physics for his work on climate modeling; Wetherald died in 2011.)

The rise of climate modeling allowed scientists to more accurately envision the impacts of global warming. In 1979, Charney and other experts met in Woods Hole, Mass., to try to put together a scientific consensus on what increasing levels of CO 2 would mean for the planet. They analyzed climate models from Manabe and from James Hansen of NASA. The resulting “Charney report” concluded that rising CO 2 in the atmosphere would lead to additional and significant climate change. The ocean might take up much of that heat, the scientists wrote — but “it appears that the warming will eventually occur, and the associated regional climatic changes so important to the assessment of socioeconomic consequence may well be significant.”

In the decades since, climate modeling has gotten increasingly sophisticated . Scientists have drawn up a variety of scenarios for how carbon emissions might change in the future, depending on the stringency of emissions cuts. Modelers use those scenarios to project how climate and weather will change around the globe, from hotter croplands in China to melting glaciers in the Himalayas. Climate simulations have also allowed researchers to identify the fingerprints of human impacts on extreme weather that is already happening, by comparing scenarios that include the influence of human activities with those that do not.

And as climate science firmed up and the most dramatic consequences became clear, the political battles raged. — Alexandra Witze

Climate science meets politics

With the development of climate science tracing back to the early Cold War, perhaps it shouldn’t be a surprise that the science of global warming became enmeshed in broader societal and political battles. A complex stew of political, national and business interests mired society in debates about the reality of climate change, and what to do about it, decades after the science became clear that humans are fundamentally altering the planet’s atmosphere.

Society has pulled itself together before to deal with global environmental problems, such as the Antarctic ozone hole. In 1974 chemists Mario Molina and F. Sherwood Rowland, both of the University of California, Irvine, reported that chlorofluorocarbon chemicals, used in products such as spray cans and refrigerants, caused a chain of reactions that gnawed away at the atmosphere’s protective ozone layer . The resulting ozone hole, which forms over Antarctica every spring, allows more ultraviolet radiation from the sun to make it through Earth’s atmosphere and reach the surface, where it can cause skin cancer and eye damage.

Governments ultimately worked under the auspices of the United Nations to craft the 1987 Montreal Protocol, which strictly limited the manufacture of chlorofluorocarbons . In the years following, the ozone hole began to heal. But fighting climate change would prove to be far more challenging. Chlorofluorocarbons were a suite of chemicals with relatively limited use and for which replacements could be found without too much trouble. But the greenhouse gases that cause global warming stem from a wide variety of human activities, from energy development to deforestation. And transforming entire energy sectors to reduce or eliminate carbon emissions is much more difficult than replacing a set of industrial chemicals.

In 1980, though, researchers took an important step toward banding together to synthesize the scientific understanding of climate change and bring it to the attention of international policy makers. It started at a small scientific conference in Villach, Austria. There, experts met under the auspices of the World Meteorological Organization, the International Council of Scientific Unions and the United Nations Environment Program to discuss the seriousness of climate change. On the train ride home from the meeting, Swedish meteorologist Bert Bolin talked with other participants about how a broader, deeper and more international analysis was needed. In 1985, a second conference was held at Villach to highlight the urgency, and in 1988, the Intergovernmental Panel on Climate Change, the IPCC, was born. Bolin was its first chairperson.

The IPCC became a highly influential and unique body. It performs no original scientific research; instead, it synthesizes and summarizes the vast literature of climate science for policy makers to consider — primarily through massive reports issued every couple of years. The first IPCC report , in 1990, predicted that the planet’s global mean temperature would rise more quickly in the following century than at any point in the last 10,000 years, due to increasing greenhouse gases in the atmosphere. Successive IPCC reports showed more and more confidence in the link between greenhouse emissions and rising global temperatures — and explored how society might mitigate and adapt to coming changes.

IPCC reports have played a key role in providing scientific information for nations discussing how to stabilize greenhouse gas concentrations. This process started with the Rio Earth Summit in 1992 , which resulted in the U.N. Framework Convention on Climate Change. Annual U.N. meetings to tackle climate change led to the first international commitments to reduce emissions, the Kyoto Protocol of 1997. Under it, developed countries committed to reduce emissions of CO 2 and other greenhouse gases. By 2007 the IPCC declared that the reality of climate warming is “unequivocal ”; the group received the Nobel Peace Prize that year along with Al Gore for their work on climate change.

The IPCC process ensured that policy makers had the best science at hand when they came to the table to discuss cutting emissions. “If you go back and look at the original U.N. framework on climate change, already you see the core of the science represented there,” says Rachel Cleetus, a climate policy expert with the Union of Concerned Scientists in Cambridge, Mass. Of course, nations did not have to abide by that science — and they often didn’t.

Throughout the 2000s and 2010s, international climate meetings discussed less hard-core science and more issues of equity. Countries such as China and India pointed out that they needed energy to develop their economies, and that nations responsible for the bulk of emissions through history, such as the United States, needed to lead the way in cutting greenhouse gases. Meanwhile, residents of some of the most vulnerable nations, such as low-lying islands that are threatened by sea level rise, gained visibility and clout at international negotiating forums. “The issues around equity have always been very uniquely challenging in this collective action problem,” says Cleetus.

By 2015, the world’s nations had made some progress on the emissions cuts laid out in the Kyoto Protocol, but it was still not enough to achieve substantial global reductions. That year, a key U.N. climate conference in Paris produced an international agreement to try to limit global warming to 2 degrees C , and preferably 1.5 degrees C, above preindustrial levels.

Every country has its own approach to the challenge of addressing climate change. In the United States, which gets approximately 80 percent of its energy from fossil fuels, sophisticated efforts to downplay and critique the science led to major delays in climate action. For decades U.S. fossil fuel companies such as ExxonMobil worked to influence politicians to take as little action on emissions reductions as possible. Working with a small group of influential scientists, this well-funded, well-orchestrated campaign took many of its tactics from earlier tobacco-industry efforts to cast doubt on the links between smoking and cancer, as historians Naomi Oreskes and Erik Conway documented in their book Merchants of Doubt.

Perhaps the peak of U.S. climate denialism came in the late 1980s and into the 1990s — roughly a century after Swedish physical chemist Svante Arrhenius laid out the consequences of putting too much carbon dioxide into the atmosphere. In 1988 NASA scientist James Hansen testified to lawmakers about the consequences of global warming. “It is already happening now,” Hansen said, summarizing what scientists had long known.

The high-profile nature of Hansen’s testimony, combined with his NASA expertise, vaulted global warming into the public eye in the United States like never before. “It really hit home with a public who could understand that there are reasons that Venus is hot and Mars is cold,” says Joshua Howe, a historian at Reed College. “And that if you use that same reasoning, we have some concerns about what is happening here on Earth.” But Hansen also kicked off a series of bitter public battles about the reality of human-caused climate change that raged for years.        

One common approach of climate skeptics was to attack the environmental data and models that underlie climate science. In 1998, scientist Michael Mann, then at the University of Massachusetts–Amherst, and colleagues published a detailed temperature record that formed the basis of what came to be known as the “hockey stick” graph, so named because the chart showed a sharp rise in temperatures (the hockey blade) at the end of a long, much flatter period (the hockey stick). Skeptics soon demanded the data and software processing tools Mann used to create the graph. Bloggers and self-proclaimed citizen scientists created a cottage industry of questioning new climate science papers under the guise of “audits.” In 2009 hackers broke into a server at the University of East Anglia, a leading climate-research hub in Norwich, England, and released more than 1,000 e-mails between climate scientists. This “Climategate” scandal purported to reveal misconduct on the part of the researchers, but several reviews largely exonerated the scientists.  

The graph that launched climate skeptic attacks

This famous graph, produced by scientist Michael Mann and colleagues, and then reproduced in a 2001 report by the Intergovernmental Panel on Climate Change, dramatically captures temperature change over time. Climate change skeptics made it the center of an all-out attack on climate science.

Such tactics undoubtedly succeeded in feeding politicians’ delay on climate action in the United States, most of it from Republicans. President George W. Bush withdrew the country from the Kyoto Protocol in 2001 ; Donald Trump similarly rejected the Paris accord in 2017 . As late as 2015, the chair of the Senate’s environment committee, James Inhofe of Oklahoma, brought a snowball into Congress on a cold winter’s day in order to continue his argument that human-caused global warming is a “hoax.” In Australia, a similar mix of right-wing denialism and fossil fuel interests has kept climate change commitments in flux, as prime ministers are voted in and out over fierce debates about how the nation should act on climate.

Yet other nations have moved forward. Some European countries such as Germany aggressively pursued renewable energies, such as wind and solar, while activists such as the Swedish teenager Greta Thunberg — the vanguard of a youth-action movement — pressured their governments for more.

In recent years the developing economies of China and India have taken center stage in discussions about climate action. Both nations argue that they must be allowed extra time to wean themselves off fossil fuels in order to continue economic growth. They note that historically speaking, the United States is the largest total emitter of carbon by far.

Total carbon dioxide emissions by country, 1850–2021

These 20 nations have emitted the largest cumulative amounts of carbon dioxide since 1850. Emissions are shown in in billions of metric tons and are broken down into subtotals from fossil fuel use and cement manufacturing (blue) as well as from land use and forestry (green).

China, whose annual CO 2 emissions surpassed those of the United States in 2006, declared several moderate steps in 2021 to reduce emissions, including that it would stop building coal-burning power plants overseas. India announced it would aim for net-zero emissions by 2070, the first time it has set a date for this goal.

Yet such pledges continue to be criticized. At the 2021 U.N. Climate Change Conference in Glasgow, Scotland, India was globally criticized for not committing to a complete phaseout of coal — although the two top emitters, China and the United States, have not themselves committed to phasing out coal. “There is no equity in this,” says Aayushi Awasthy, an energy economist at the University of East Anglia. — Alexandra Witze

Facing a warmer future

Climate change creeps up gradually on society, except when it doesn’t. The slow increase in sea level, for instance, causes waters to lap incrementally higher at shorelines year after year. But when a big storm comes along — which may be happening more frequently due to climate change — the consequences become much more obvious. Storm surge rapidly swamps communities and wreaks disproportionate havoc. That’s why New York City installed floodgates in its subway and tunnel system in the wake of 2012’s Superstorm Sandy , and why the Pacific island nation of Tuvalu has asked Australia and New Zealand to be prepared to take in refugees fleeing from rising sea levels.

The list of climate impacts goes on and on — and in many cases, changes are coming faster than scientists had envisioned a few decades ago. The oceans are becoming more acidic as they absorb carbon dioxide, harming tiny marine organisms that build protective calcium carbonate shells and are the base of the marine food web. Warmer waters are bleaching coral reefs. Higher temperatures are driving animal and plant species into areas in which they previously did not live, increasing the risk of extinction for many. “It’s no longer about impacts in the future,” says Rachel Cleetus, a climate policy expert at the Union of Concerned Scientists. “It’s about what’s happening in the U.S. here and now, and around the world.”

No place on the planet is unaffected. In many areas, higher temperatures have led to major droughts, which dry out vegetation and provide additional fuel for wildfires such as those that have devastated Australia , the Mediterranean and western North America in recent years. The Colorado River , the source of water for tens of millions of people in the western United States , came under a water-shortage alert in 2021 for the first time in history.

Then there’s the Arctic, where temperatures are rising at more than twice the global average and communities are at the forefront of change. Permafrost is thawing, destabilizing buildings, pipelines and roads. Caribou and reindeer herders worry about the increased risk of parasites to the health of their animals. With less sea ice available to buffer the coast from storm erosion, the Inupiat village of Shishmaref, Alaska, risks crumbling into the sea. It will need to move from its sand-barrier island to the mainland .

“We know these changes are happening and that the Titanic is sinking,” says Louise Farquharson, a geomorphologist at the University of Alaska in Fairbanks who monitors permafrost and coastal change around Alaska. Like many Arctic scientists, she is working with Indigenous communities to understand the shifts they’re experiencing and what can be done when buildings start to slump and water supplies start to drain away. “A big part is just listening to community members and understanding what they’re seeing change,” she says.

All around the planet, those who depend on intact ecosystems for their survival face the greatest threat from climate change. And those with the least resources to adapt to climate change are the ones who feel it first .

“We are going to warm,” says Claudia Tebaldi, a climate scientist at Lawrence Berkeley National Laboratory in California. “There is no question about it. The only thing that we can hope to do is to warm a little more slowly.”

That’s one reason why the IPCC report released in 2021 focuses on anticipated levels of global warming. There is a big difference between the planet warming 1.5 degrees versus 2 degrees or 2.5 degrees. Consider that we are now at least 1.1 degrees above preindustrial levels of CO 2 and are already seeing dramatic shifts in climate. Given that, keeping further global temperature increases as low as possible will make a big difference in the climate impacts the planet faces. “With every fraction of a degree of warming, everything gets a little more intense,” says paleoclimatologist Jessica Tierney. “There’s no more time to beat around the bush.”

Historical and projected global temperature change

Various scenarios for how greenhouse gas emissions might change going forward help scientists predict future climate change. This graph shows the simulated historical temperature trend along with future projections of global surface temperature based on five scenarios from the Intergovernmental Panel on Climate Change. Temperature change is the difference from the 1850–1900 average.

The future rests on how much nations are willing to commit to cutting emissions and whether they will stick to those commitments. It’s a geopolitical balancing act the likes of which the world has never seen.

Science can and must play a role going forward. Improved climate models will illuminate what changes are expected at the regional scale, helping officials prepare. Governments and industry have crucial parts to play as well. They can invest in technologies, such as carbon sequestration, to help decarbonize the economy and shift society toward more renewable sources of energy. “We can solve these problems — most of the tools are already there,” says Cascade Tuholske, a geographer at Columbia University. “We just have to do it.”

Huge questions remain. Do voters have the will to demand significant energy transitions from their governments? How can business and military leaders play a bigger role in driving climate action? What should be the role of low-carbon energy sources that come with downsides, such as nuclear energy ? How can developing nations achieve a better standard of living for their people while not becoming big greenhouse gas emitters? How can we keep the most vulnerable from being disproportionately harmed during extreme events, and incorporate environmental and social justice into our future?

These questions become more pressing each year, as CO 2 accumulates in our atmosphere. The planet is now at higher levels of CO 2 than at any time in the last 3 million years. Yet Ralph Keeling, keeper of the iconic Mauna Loa record tracking the rise in atmospheric CO 2 , is already optimistically thinking about how scientists would be able to detect a slowdown, should the world actually start cutting emissions by a few percent per year. “That’s what the policy makers want to see — that there’s been some large-scale impact of what they did,” he says.

At the 2021 U.N. climate meeting in Glasgow diplomats from around the world agreed to work more urgently to shift away from using fossil fuels. They did not, however, adopt targets strict enough to keep the world below a warming of 1.5 degrees Celsius. It’s been well over a century since Svante Arrhenius recognized the consequences of putting extra carbon dioxide into the atmosphere, and yet world leaders have yet to pull together to avoid the most dangerous consequences of climate change.

Time is running out. — Alexandra Witze

Climate change facts

We know that climate change and its consequences are real, and we are responsible. Here’s what the science tells us.

How much has the planet warmed over the past century?

The planet’s average surface temperature has risen by at least 1.1 degree Celsius since preindustrial levels of 1850–1900.

What is causing climate change?

People are loading the atmosphere with carbon dioxide and other heat-trapping gases produced during the burning of fossil fuels, such as coal and gas, and cutting down forests.

What are some of the effects of climate change?

Ice sheets in Greenland and Antarctica are melting, raising sea levels and flooding low-lying island nations and coastal cities. Drought is parching farmlands and the rivers that feed them. Wildfires are raging. Rains are becoming more intense, and weather patterns are shifting.

What is the greenhouse effect?

In the 19th century, Irish physicist John Tyndall found that carbon dioxide gas, as well as water vapor, absorbed more heat than air alone. He argued that such gases would trap heat in Earth’s atmosphere, much as panes of glass trap heat in a greenhouse, and thus modulate climate.

What is the Keeling curve?

One of the most iconic datasets in all of science, the Keeling curve tracks the rise of atmospheric CO 2 . When geochemist Charles David Keeling began his measurements in 1958 on the Hawaiian volcano of Mauna Loa, CO 2 made up 315 parts per million of the global atmosphere. Each year the curve keeps going up: In 2016 it passed 400 ppm of CO 2 in the atmosphere, as measured during its typical annual minimum in September. In 2021, the annual minimum was 413 ppm.

Does it get hotter every year?

Average global temperatures fluctuate from year to year, but temperature observations taken at weather stations around the world confirm that we are living in the hottest years on record. The 10 warmest years since record keeping began in 1880 have all occurred since 2005. And nine of those 10 have come since 2010.

What countries emit the most carbon dioxide?

The United States has been the largest total emitter of carbon dioxide by far, followed by China and Russia. China’s annual CO 2 emissions surpassed those of the United States in 2006.

What places are impacted by climate change?

No place on the planet is unaffected. Higher temperatures have led to major droughts, providing fuel for wildfires such as those that have devastated Australia , the Mediterranean and western North America in recent years. The Colorado River came under a water-shortage alert in 2021 for the first time in history. In the Arctic, where temperatures are rising at more than twice the global average, permafrost is thawing, destabilizing buildings, pipelines and roads. With less sea ice available to buffer the coast from storm erosion, the Inupiat village of Shishmaref, Alaska, risks crumbling into the sea. All around the planet, those who depend on intact ecosystems for their survival face the greatest threat from climate change. And those with the least resources to adapt to climate change are the ones who feel it first .

Editor’s note: This story was published March 10, 2022.

British mathematician Lewis Fry Richardson (shown at center) proposes forecasting the weather by piecing together the calculations of tens of thousands of meteorologists working on small parts of the atmosphere.

Geochemist Charles David Keeling (shown in 1988) begins tracking the rise in atmospheric carbon dioxide at Mauna Loa in Hawaii. The record, which continues through today, has become one of the most iconic datasets in all of science.

Rachel Carson (shown) publishes the book Silent Spring , raising alarm over the ecological impacts of the pesticide DDT. The book helps catalyze the modern U.S. environmental movement.

The first Earth Day, organized by U.S. senator Gaylord Nelson and graduate student Denis Hayes, is celebrated.

The first Landsat satellite launched (shown), opening the door to continuous monitoring of Earth and its features from above.

A powerful eruption from the Philippines’ Mount Pinatubo (shown) ejects millions of tons of sulfur dioxide into the stratosphere, temporarily cooling the planet.  

World leaders gathered (shown) at the United Nations Conference on Environment and Development in Rio de Janeiro to address how to pursue economic development while also protecting the Earth. The meeting resulted in an international convention on climate change.

Activist Greta Thunberg initiates the “School Strike for Climate” movement by protesting outside the Swedish parliament. Soon, students around the world join a growing movement demanding action on climate change . (Activists at the 2021 U.N. Climate Change Conference are shown.)

From the archive

Climate change foreseen.

In an early mention of climate change in Science News-Letter , the predecessor of Science News , British meteorologist C.E.P. Brooks warns that present warming trends could lead to “important economic and political effects.”

IGY Brings Many Discoveries

Science News Letter lists the Top 8 accomplishments of the International Geophysical Year.

Chilling possibilities

Science News explores the tentative idea that global temperatures are cooling and that a new ice age could be imminent, which is later shown to be inaccurate.

Long Hot Future: Warmer Earth Appears Inevitable

“The planet earth will be a warmer place in the 21st century, and there is no realistic strategy that can prevent the change,” Science News reports.

Ozone and Global Warming: What to Do?

Policy makers discuss how to solve the dual problems of ozone depletion and global warming.

Looking for Mr. Greenhouse

Science writer Richard Monastersky reports on scientists’ efforts to evaluate how to connect increasing greenhouse gases and a warming climate.

World Climate Panel Charts Path for Action

The Intergovernmental Panel on Climate Change reports that “the fingerprint of man in the past temperature record” is now apparent.

Animals on the Move

A warming climate means shifting ranges and ecosystem disruptions for a lot of species, Nancy Ross-Flanigan reports.

Changing climate: 10 years after ‘An Inconvenient Truth’

A decade after former vice president Al Gore releases the documentary film An Inconvenient Truth , Science News looks back at how climate science has advanced.

With nowhere to hide from rising seas, Boston prepares for a wetter future

Mary Caperton Morton reports for Science News on how Boston is taking action to prepare for rising seas.

The new UN climate change report shows there’s no time for denial or delay

Earth & climate writer Carolyn Gramling covers the sixth assessment report from the Intergovernmental Panel on Climate Change, which documents how climate change is already affecting every region on Earth.

Climate change disinformation is evolving. So are efforts to fight back

Researchers are testing games and other ways to help people recognize climate change denial.

Extreme weather in 2022 showed the global impact of climate change

Heat waves, floods, wildfires and drought around the world were exacerbated by Earth’s changing climate.

It’s possible to reach net-zero carbon emissions. Here’s how

Cutting carbon dioxide emissions to curb climate change and reach net zero is possible but not easy.

The last 12 months were the hottest on record

The planet’s average temperature was about 1.3 degrees Celsius higher than the 1850–1900 average, a new report finds.

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4 guidelines for writing about climate change

The climate story has moved beyond science and is increasingly local . It touches communities and coverage in new ways every day. As you cover the topic in your area, here are some guidelines for your reporting.

Do not conflate science and policy. They are separate things. Science informs policymaking but it does not dictate what policies should be chosen. Different people may reach different conclusions, depending on what they value.

Be specific about which climate change “debate” you are covering. There is no single debate; there are separate debates within science, within policy and within economics, and debates about how scientific findings should guide policy.

Be clear about the science. The overarching issue is as settled as things get in science: The planet is warming and humans are largely responsible. As a result, glaciers and ice sheets are melting. New, contradictory evidence could come along–science is always subject to revision. But the idea that humans are causing climate change is not scientifically controversial.

Avoid “global warming: yes or no?” coverage. Although there are still many scientific questions to be answered, the climate change story has shifted to policy. What should we do, if anything, about climate change? Just as governments routinely make decisions about fiscal policy under great uncertainty, environmental policy can proceed even though scientific uncertainties remain.

Taken from Covering Climate Change , a self-directed course by Tom Yulsman at Poynter NewsU .

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Sanctuaries resource collection: Climate change

Though we often think about human-induced climate change as something that will happen in the future, it is an ongoing process. Ecosystems and communities in the United States and around the world are being impacted today. 

A collage of typical climate and weather-related events: floods, heatwaves, drought, hurricanes, wildfires and loss of glacial ice. (Image credit: NOAA)

Global temperatures rose about 1.98°F offsite link (1.1°C) from 1901 to 2020, but climate change refers to more than an increase in temperature. It also includes sea level rise, changes in weather patterns like drought and flooding, and much more. Things that we depend upon and value — water, energy, transportation, wildlife, agriculture, ecosystems, and human health — are experiencing the effects of a changing climate.

A complex issue

The impacts of climate change on different sectors of society are interrelated. Drought can harm food production and human health. Flooding can lead to disease spread and damages to ecosystems and infrastructure. Human health issues can increase mortality, impact food availability, and limit worker productivity. Climate change impacts are seen throughout every aspect of the world we live in. However, climate change impacts are uneven across the country and the world — even within a single community, climate change impacts can differ between neighborhoods or individuals. Long-standing socioeconomic inequities can make  underserved groups, who often have the highest exposure to hazards and the fewest resources to respond, more vulnerable. 

The projections of a climate change-impacted future are not inevitable. Many of the problems and solutions offsite link are known to us now, and ongoing research continues to provide new ones.  Experts believe there is still time to avoid the most negative of outcomes by limiting warming offsite link   and reducing emissions to zero as quickly as possible. Reducing our emissions of greenhouse gases will require investment in new technology and infrastructure, which will spur job growth. Additionally, lowering emissions will lessen harmful impacts to human health, saving countless lives and billions of dollars in health-related expenses.

Levels of the two most important anthropogenic greenhouse gases, carbon dioxide and methane, continued their unrelenting rise in 2020 despite the economic slowdown caused by the coronavirus pandemic response.

Our changing climate

We see climate change affecting our planet from pole to pole. NOAA monitors global climate data and here are some of the changes NOAA has recorded. You can explore more at the Global Climate Dashboard .

• Global temperatures rose about 1.8°F (1°C) from 1901 to 2020.
• Sea level rise has accelerated from 1.7 mm/year throughout most of the twentieth century to 3.2 mm/year since 1993.
• Glaciers are shrinking: average thickness of 30 well-studied glaciers has decreased more than 60 feet since 1980.
• The area covered by sea ice in the Arctic at the end of summer has shrunk by about 40% since 1979.
• The amount of carbon dioxide in the atmosphere has risen by 25% since 1958, and by about 40% since the Industrial Revolution.
• Snow is melting earlier compared to long-term averages.

Changes to water resources can have a big impact on our world and our lives.

Flooding is an increasing issue as our climate is changing. Compared to the beginning of the 20th century, there are both stronger and more frequent abnormally heavy precipitation events across most of the United States.

Conversely, drought is also becoming more common , particularly in the Western United States. Humans are using more water, especially for agriculture. Much like we sweat more when it is hot out, higher air temperatures cause plants to lose, or transpire , more water, meaning farmers must give them more water. Both highlight the need for more water in places where supplies are dwindling.

Snowpack is an important source of fresh water for many people. As the snow melts, fresh water becomes available for use, especially in regions like the Western United States where there is not much precipitation in warmer months. But as temperatures warm, there is less snow overall and snow begins to melt earlier in the year, meaning snowpack may not be a reliable source of water for the entire warm and dry seasons. 

The Redlands Mesa area outside Hotchkiss, Colorado, is particularly at risk to wildfires, but with funding from NOAA’s Environmental Literacy Program, local high school students are taking action to tackle their community’s vulnerability to this hazard.

Our food supply depends on climate and weather conditions. Although farmers and researchers may be able to adapt some agricultural techniques and technologies or develop new ones, some changes will be difficult to manage. Increased temperatures, drought and water stress, diseases, and weather extremes create challenges for the farmers and ranchers who put food on our tables.

Human farm workers can suffer from heat-related health issues , like exhaustion, heatstroke, and heart attacks. Rising temperatures and heat stress can also harm livestock. 

Human health

Climate change is already impacting human health . Changes in weather and climate patterns can put lives at risk. Heat is one of the most deadly weather phenomena. As ocean temperatures rise, hurricanes are getting stronger and wetter , which can cause direct and indirect deaths . Dry conditions lead to more wildfires, which bring many health risks . Higher incidences of flooding can lead to the spread of waterborne diseases, injuries, and chemical hazards. As geographic ranges of mosquitoes and ticks expand, they can carry diseases to new locations.

The most vulnerable groups, including children, the elderly, people with preexisting health conditions, outdoor workers, people of color, and people with low income, are at an even higher risk because of the compounding factors from climate change. But public health groups can work with local communities to help people understand and build resilience to climate change health impacts.

The environment

Climate change will continue to have a significant impact on ecosystems and organisms, though they are not impacted equally. The Arctic is one of the ecosystems most vulnerable to the effects of climate change, as it is warming at least twice the rate of the global average and melting land ice sheets offsite link and glaciers offsite link contribute dramatically to sea level rise around the globe.

Some living things are able to respond to climate change; some plants are blooming earlier and some species may expand their geographic range. But these changes are happening too fast for many other plants and animals as increasing temperatures and changing precipitation patterns stress ecosystems. Some invasive or nuisance species, like lionfish and ticks , may thrive in even more places because of climate change. 

Changes are also occurring in the ocean. The ocean absorbs about 30% of the carbon dioxide that is released into the atmosphere from the burning of fossil fuels. As a result, the water is becoming more acidic , affecting marine life. Sea levels are rising due to thermal expansion, in addition to melting ice sheets and glaciers, putting coastal areas at greater risk of erosion and storm surge.

The compounding effects of climate change are leading to many changes in ecosystems. Coral reefs are vulnerable to many effects of climate change: warming waters can lead to coral bleaching, stronger hurricanes can destroy reefs, and sea level rise can cause corals to be smothered by sediment. Coral reef ecosystems are home to thousands of species, which rely on healthy coral reefs to survive.

Infrastructure

Physical infrastructure includes bridges, roads, ports, electrical grids, broadband internet, and other parts of our transportation and communication systems. It is often designed to be in use for years or decades, and many communities have infrastructure that was designed without future climate in mind. But even newer infrastructures can be vulnerable to climate change. 

Extreme weather events that bring heavy rains, floods, wind, snow, or temperature changes can stress existing structures and facilities. Increased temperatures require more indoor cooling, which can put stress on an energy grid. Sudden heavy rainfall can lead to flooding that shuts down highways and major business areas. 

Nearly 40% of the United States population lives in coastal counties, meaning millions of people will be impacted by sea level rise. Coastal infrastructure , such as roads, bridges, water supplies, and much more, is at risk. Sea level rise can also lead to coastal erosion and high-tide flooding . Some communities are projected to possibly end up at or below sea level by 2100 and will face decisions around managed retreat and climate adaptation. 

Many communities are not yet prepared to face climate-related threats. Even within a community, some groups are more vulnerable to these threats than others. Going forward, it is important for communities to invest in resilient infrastructure that will be able to withstand future climate risks. Researchers are studying current and future impacts of climate change on communities and can offer recommendations on best practices. Resilience education is vitally important for city planners, emergency managers, educators, communicators, and all other community members to prepare for climate change.

EDUCATION CONNECTION

Teaching about climate change can be a daunting challenge, but it is a critical field for students to learn about, as it affects many parts of society. The Essential Principles of Climate Literacy , developed by NOAA and other federal partners, are standards that create a framework for teaching climate. The Toolbox for Teaching Climate & Energy explores a learning process to help students engage in climate action in their own communities or on a global scale. For more educator support, NOAA offers professional development opportunities (including the Planet Stewards Program ) about climate and other topics.

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What Is Climate Change?

Climate change refers to long-term shifts in temperatures and weather patterns. Such shifts can be natural, due to changes in the sun’s activity or large volcanic eruptions. But since the 1800s, human activities have been the main driver of climate change , primarily due to the burning of fossil fuels like coal, oil and gas.

Burning fossil fuels generates greenhouse gas emissions that act like a blanket wrapped around the Earth, trapping the sun’s heat and raising temperatures.

The main greenhouse gases that are causing climate change include carbon dioxide and methane. These come from using gasoline for driving a car or coal for heating a building, for example. Clearing land and cutting down forests can also release carbon dioxide. Agriculture, oil and gas operations are major sources of methane emissions. Energy, industry, transport, buildings, agriculture and land use are among the main sectors  causing greenhouse gases.

Humans are responsible for global warming

Climate scientists have showed that humans are responsible for virtually all global heating over the last 200 years. Human activities like the ones mentioned above are causing greenhouse gases that are warming the world faster than at any time in at least the last two thousand years.

The average temperature of the Earth’s surface is now about 1.1°C warmer than it was in the late 1800s (before the industrial revolution) and warmer than at any time in the last 100,000 years. The last decade (2011-2020) was the warmest on record , and each of the last four decades has been warmer than any previous decade since 1850.

Many people think climate change mainly means warmer temperatures. But temperature rise is only the beginning of the story. Because the Earth is a system, where everything is connected, changes in one area can influence changes in all others.

The consequences of climate change now include, among others, intense droughts, water scarcity, severe fires, rising sea levels, flooding, melting polar ice, catastrophic storms and declining biodiversity.

People are experiencing climate change in diverse ways

Climate change can affect our health , ability to grow food, housing, safety and work. Some of us are already more vulnerable to climate impacts, such as people living in small island nations and other developing countries. Conditions like sea-level rise and saltwater intrusion have advanced to the point where whole communities have had to relocate, and protracted droughts are putting people at risk of famine. In the future, the number of people displaced by weather-related events is expected to rise.

Every increase in global warming matters

In a series of UN reports , thousands of scientists and government reviewers agreed that limiting global temperature rise to no more than 1.5°C would help us avoid the worst climate impacts and maintain a livable climate. Yet policies currently in place point to a 3°C temperature rise by the end of the century.

The emissions that cause climate change come from every part of the world and affect everyone, but some countries produce much more than others .The seven biggest emitters alone (China, the United States of America, India, the European Union, Indonesia, the Russian Federation, and Brazil) accounted for about half of all global greenhouse gas emissions in 2020.

Everyone must take climate action, but people and countries creating more of the problem have a greater responsibility to act first.

We face a huge challenge but already know many solutions

Many climate change solutions can deliver economic benefits while improving our lives and protecting the environment. We also have global frameworks and agreements to guide progress, such as the Sustainable Development Goals , the UN Framework Convention on Climate Change and the Paris Agreement . Three broad categories of action are: cutting emissions, adapting to climate impacts and financing required adjustments.

Switching energy systems from fossil fuels to renewables like solar or wind will reduce the emissions driving climate change. But we have to act now. While a growing number of countries is committing to net zero emissions by 2050, emissions must be cut in half by 2030 to keep warming below 1.5°C. Achieving this means huge declines in the use of coal, oil and gas: over two-thirds of today’s proven reserves of fossil fuels need to be kept in the ground by 2050 in order to prevent catastrophic levels of climate change.

Adapting to climate consequences protects people, homes, businesses, livelihoods, infrastructure and natural ecosystems. It covers current impacts and those likely in the future. Adaptation will be required everywhere, but must be prioritized now for the most vulnerable people with the fewest resources to cope with climate hazards. The rate of return can be high. Early warning systems for disasters, for instance, save lives and property, and can deliver benefits up to 10 times the initial cost.

We can pay the bill now, or pay dearly in the future

Climate action requires significant financial investments by governments and businesses. But climate inaction is vastly more expensive. One critical step is for industrialized countries to fulfil their commitment to provide $100 billion a year to developing countries so they can adapt and move towards greener economies.

To get familiar with some of the more technical terms used in connection with climate change, consult the Climate Dictionary .

Learn more about…

The facts on climate and energy

Climate change is a hot topic – with myths and falsehoods circulating widely. Find some essential facts here .

The science

See the latest climate reports from the United Nations as well as climate action facts .

Causes and Effects

Fossil fuels are by far the largest contributor to the greenhouse gas emissions that cause climate change, which poses many risks to all forms of life on Earth. Learn more .

From the Secretary-General

Read the UN Chief’s latest statements on climate action.

What is net zero? Why is it important? Our  net-zero page  explains why we need steep emissions cuts now and what efforts are underway.

Renewable energy – powering a safer future

What is renewable energy and why does it matter? Learn more about why the shift to renewables is our only hope for a brighter and safer world.

How will the world foot the bill? We explain the issues and the value of financing climate action.

What is climate adaptation? Why is it so important for every country? Find out how we can protect lives and livelihoods as the climate changes.

Climate Issues

Learn more about how climate change impacts are felt across different sectors and ecosystems.

Why women are key to climate action

Women and girls are on the frontlines of the climate crisis and uniquely situated to drive action. Find out why it’s time to invest in women.

Facts and figures

• What is climate change?
• Causes and effects
• Myth busters

Cutting emissions

• Explaining net zero
• High-level expert group on net zero
• Checklists for credibility of net-zero pledges
• Greenwashing
• What you can do

Clean energy

• Renewable energy – key to a safer future
• What is renewable energy
• Five ways to speed up the energy transition
• Why invest in renewable energy
• Clean energy stories
• A just transition

Adapting to climate change

• Climate adaptation
• Early warnings for all
• Youth voices

Financing climate action

• Finance and justice
• Loss and damage
• $100 billion commitment
• Why finance climate action
• Biodiversity
• Human Security

International cooperation

• What are Nationally Determined Contributions
• Acceleration Agenda
• Climate Ambition Summit
• Climate conferences (COPs)
• Youth Advisory Group
• Action initiatives
• Secretary-General’s speeches
• Press material
• Fact sheets
• Communications tips

What Are the Effects of Climate Change?

A rapidly warming planet poses an existential threat to all life on earth. Just how bad it gets depends on how quickly we act.

An area flooded by Super Typhoon Noru in the Bulacan Province of the Philippines, September 26, 2022

Rouelle Umali/Xinhua via Getty Images

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Climate change is our planet’s greatest existential threat . If we don’t limit greenhouse gas emissions from the burning of fossil fuels, the consequences of rising global temperatures include massive crop and fishery collapse, the disappearance of hundreds of thousands of species, and entire communities becoming uninhabitable. While these outcomes may still be avoidable, climate change is already causing suffering and death. From raging wildfires and supercharged storms, its compounding effects can be felt today, outside our own windows.

Understanding these impacts can help us prepare for what’s here, what’s avoidable, and what’s yet to come, and to better prepare and protect all communities. Even though everyone is or will be affected by climate change, those living in the world’s poorest countries—which have contributed least to the problem—are the most climate-vulnerable. They have the fewest financial resources to respond to crises or adapt, and they’re closely dependent on a healthy, thriving natural world for food and income. Similarly, in the United States, it is most often low-income communities and communities of color that are on the frontlines of climate impacts. And because climate change and rising inequality are interconnected crises, decision makers must take action to combat both—and all of us must fight for climate justice. Here’s what you need to know about what we’re up against.

Effects of climate change on weather

Effects of climate change on the environment, effects of climate change on agriculture, effects of climate change on animals, effects of climate change on humans, future effects of climate change.

As global temperatures climb, widespread shifts in weather systems occur, making events like droughts , hurricanes , and floods more intense and unpredictable. Extreme weather events that may have hit just once in our grandparents’ lifetimes are becoming more common in ours. However, not every place will experience the same effects: Climate change may cause severe drought in one region while making floods more likely in another.

Already, the planet has warmed 1.1 degrees Celsius (1.9 degrees Fahrenheit) since the preindustrial era began 250 years ago, according to the Intergovernmental Panel on Climate Change (IPCC) . And scientists warn it could reach a worst-case scenario of 4 degrees Celsius (7.2 degrees Fahrenheit) by 2100 if we fail to tackle the causes of climate change —namely, the burning of fossil fuels (coal, oil, and gas) .

Tokyo during a record-breaking heat wave, August 13, 2020

The Yomiuri Shimbun via AP Images

Higher average temperatures

This change in global average temperature—seemingly small but consequential and climbing—means that, each summer, we are likely to experience increasingly sweltering heat waves. Even local news meteorologists are starting to connect strings of record-breaking days to new long-term trends, which are especially problematic in regions where infrastructure and housing have not been built with intensifying heat in mind. And heat waves aren’t just uncomfortable—they’re the leading cause of weather-related fatalities in the United States.

Longer-lasting droughts

Hotter temperatures increase the rate at which water evaporates from the air, leading to more severe and pervasive droughts . Already, climate change has pushed the American West into a severe “megadrought”—the driest 22-year stretch recorded in at least 1,200 years—shrinking drinking water supplies, withering crops , and making forests more susceptible to insect infestations. Drought can also create a positive feedback loop in which drier soil and less plant cover cause even faster evaporation.

More intense wildfires

This drier, hotter climate also creates conditions that fuel more vicious wildfire seasons—with fires that spread faster and burn longer—putting millions of additional lives and homes at risk. The number of large wildfires doubled between 1984 and 2015 in the western United States. And in California alone, the annual area burned by wildfires increased 500 percent between 1972 and 2018.

Evacuation after Hurricane Harvey in Houston, August 28, 2017

David J. Phillip/AP Photo

Stronger storms

Warmer air also holds more moisture, making tropical cyclones wetter, stronger, and more capable of rapidly intensifying. In the latest report from the IPCC , scientists found that daily rainfall during extreme precipitation events would increase by about 7 percent for each degree Celsius of global warming, increasing the dangers of flooding . The frequency of severe Category 4 and 5 hurricanes is also expected to increase. In 2017, Hurricane Harvey, a devastating Category 4 storm, dumped a record 275 trillion pounds of rain and resulted in dozens of deaths in the Houston area.

From the poles to the tropics, climate change is disrupting ecosystems. Even a seemingly slight shift in temperature can cause dramatic changes that ripple through food webs and the environment.

The lake at Jökulsárlón, a glacial lagoon in Iceland, which has grown because of continued glacial melting

Eskinder Debebe/UN Photo

Melting sea ice

The effects of climate change are most apparent in the world’s coldest regions—the poles. The Arctic is heating up twice as fast as anywhere else on earth, leading to the rapid melting of glaciers and polar ice sheets, where a massive amount of water is stored. As sea ice melts, darker ocean waters that absorb more sunlight become exposed, creating a positive feedback loop that speeds up the melting process. In just 15 years, the Arctic could be entirely ice-free in the summer.

Sea level rise

Scientists predict that melting sea ice and glaciers, as well as the fact that warmer water expands in volume, could cause sea levels to rise as much as 6.6 feet by the end of the century, should we fail to curb emissions. The extent (and pace) of this change would devastate low-lying regions, including island nations and densely populated coastal cities like New York City and Mumbai.

But sea level rise at far lower levels is still costly, dangerous, and disruptive. According to the 2022 Sea Level Rise Technical Report from the National Ocean Service, the United States will see a foot of sea level rise by 2050, which will regularly damage infrastructure, like roads, sewage treatment plants, and even power plants . Beaches that families have grown up visiting may be gone by the end of the century. Sea level rise also harms the environment, as encroaching seawater can both erode coastal ecosystems and invade freshwater inland aquifers, which we rely on for agriculture and drinking water. Saltwater incursion is already reshaping life in nations like Bangladesh , where one-quarter of the lands lie less than 7 feet above sea level.

A waterlogged road, caused by rainstorm and upstream flood discharge, in the Shaoguan, Guangdong Province of China, June 21, 2022

Stringer/Anadolu Agency via Getty Images

In addition to coastal flooding caused by sea level rise, climate change influences the factors that result in inland and urban flooding: snowmelt and heavy rain. As global warming continues to both exacerbate sea level rise and extreme weather, our nation’s floodplains are expected to grow by approximately 45 percent by 2100. In 2022, deadly flooding in Pakistan—which inundated as much as a third of the country—resulted from torrential rains mixed with melting glaciers and snow.

Warmer ocean waters and marine heat waves

Oceans are taking the brunt of our climate crisis. Covering more than 70 percent of the planet’s surface, oceans absorb 93 percent of all the heat that’s trapped by greenhouse gases and up to 30 percent of all the carbon dioxide emitted from burning fossil fuels.

Temperature-sensitive fish and other marine life are already changing migration patterns toward cooler and deeper waters to survive, sending food webs and important commercial fisheries into disarray. And the frequency of marine heat waves has increased by more than a third . These spikes have led to mass die-offs of plankton and marine mammals.

To make matters worse, the elevated absorption of carbon dioxide by the ocean leads to its gradual acidification , which alters the fundamental chemical makeup of the water and threatens marine life that has evolved to live in a narrow pH band. Animals like corals, oysters, and mussels will likely feel these effects first, as acidification disrupts the calcification process required to build their shells.

Ecosystem stressors

Land-based ecosystems—from old-growth forests to savannahs to tropical rainforests—are faring no better. Climate change is likely to increase outbreaks of pests, invasive species, and pathogen infections in forests. It’s changing the kinds of vegetation that can thrive in a given region and disrupting the life cycles of wildlife, all of which is changing the composition of ecosystems and making them less resilient to stressors. While ecosystems have the capacity to adapt, many are reaching the hard limits of that natural capacity . More repercussions will follow as temperatures rise.

Climate change appears to be triggering a series of cascading ecological changes that we can neither fully predict nor, once they have enough momentum, fully stop. This ecosystem destabilization may be most apparent when it comes to keystone species that have an outsize- role in holding up an ecosystem’s structure.

Coffee plants destroyed by frost due to extremely low temperatures near Caconde in the São Paulo state of Brazil, August 25, 2021

Jonne Roriz/Bloomberg via Getty Images

Less predictable growing seasons

In a warming world, farming crops is more unpredictable—and livestock, which are sensitive to extreme weather, become harder to raise. Climate change shifts precipitation patterns, causing unpredictable floods and longer-lasting droughts. More frequent and severe hurricanes can devastate an entire season’s worth of crops. Meanwhile, the dynamics of pests, pathogens, and invasive species—all of which are costly for farmers to manage—are also expected to become harder to predict. This is bad news, given that most of the world’s farms are small and family-run. One bad drought or flood could decimate an entire season’s crop or herd. For example, in June 2022, a triple-digit heat wave in Kansas wiped out thousands of cows. While the regenerative agriculture movement is empowering rural communities to make their lands more resilient to climate change, unfortunately, not all communities can equitably access the support services that can help them embrace these more sustainable farming tactics.

Reduced soil health

Healthy soil has good moisture and mineral content and is teeming with bugs, bacteria, fungi, and microbes that in turn contribute to healthy crops. But climate change, particularly extreme heat and changes in precipitation, can degrade soil quality. These impacts are exacerbated in areas where industrial, chemical-dependent monoculture farming has made soil and crops less able to withstand environmental changes.

Food shortages

Ultimately, impacts to our agricultural systems pose a direct threat to the global food supply. And food shortages and price hikes driven by climate change will not affect everyone equally: Wealthier people will continue to have more options for accessing food, while potentially billions of others will be plummeted into food insecurity—adding to the billions that already have moderate or severe difficulty getting enough to eat.

The poison dart frog’s survival is currently threatened by habitat loss and climate change.

Chris Mattison/Minden Pictures

It’s about far more than just the polar bears: Half of all animal species in the world’s most biodiverse places, like the Amazon rainforest and the Galapagos Islands, are at risk of extinction from climate change. And climate change is threatening species that are already suffering from the biodiversity crisis, which is driven primarily by changes in land and ocean use (like converting wild places to farmland) and direct exploitation of species (like overfishing and wildlife trade). With species already in rough shape—more than 500,000 species have insufficient habitat for long-term survival—unchecked climate change is poised to push millions over the edge.

Climate change rapidly and fundamentally alters (or in some cases, destroys) the habitat that wildlife have incrementally adapted to over millennia. This is especially harmful for species’ habitats that are currently under threat from other causes. Ice-dependent mammals like walruses and penguins, for example, won’t fare well as ice sheets shrink. Rapid shifts in ocean temperatures stress the algae that nourishes coral reefs, causing reefs to starve—an increasingly common phenomenon known as coral bleaching . Disappearing wetlands in the Midwest’s Prairie Pothole Region means the loss of watering holes and breeding grounds for millions of migratory birds. (Many species are now struggling to survive, as more than 85 percent of wetlands have been lost since 1700). And sea level rise will inundate or erode away many coastal habitats, where hundreds of species of birds, invertebrates, and other marine species live.

Many species’ behaviors—mating, feeding, migration—are closely tied to subtle seasonal shifts, as in temperature , precipitation level, and foliage. In some cases, changes to the environment are happening quicker than species are able to adapt. When the types and quantity of plant life change across a region, or when certain species bloom or hatch earlier or later than in the past, it impacts food and water supplies and reverberates up food chains.

Wildfire smoke–filled air in Multnomah County, Oregon, September 16, 2020

Motoya Nakamura/Multnomah County Communications, CC BY NC-ND 4.0

Ultimately, the way climate change impacts weather, the environment, animals, and agriculture affects humanity as well. But there’s more. Around the world, our ways of life—from how we get our food to the industries around which our economies are based—have all developed in the context of relatively stable climates. As global warming shakes this foundation, it promises to alter the very fabric of society. At worst, this could lead to widespread famine, disease, war, displacement , injury, and death. For many around the world, this grim forecast is already their reality. In this way, climate change poses an existential threat to all human life.

Human health

Climate change worsens air quality . It increases exposure to hazardous wildfire smoke and ozone smog triggered by warmer conditions, both of which harm our health, particularly for those with pre-existing illnesses like asthma or heart disease.

Insect-borne diseases like malaria and Zika become more prevalent in a warming world as their carriers are able to exist in more regions or thrive for longer seasons. In the past 30 years, the incidence of Lyme disease from ticks has nearly doubled in the United States, according to the U.S. Environmental Protection Agency (EPA). Thousands of people face injury, illness , and death every year from more frequent or more intense extreme weather events. At a 2-degree Celsius rise in global average temperature, an estimated one billion people will face heat stress risk. In the summer of 2022 alone, thousands died in record-shattering heat waves across Europe. Weeks later, dozens were killed by record-breaking urban flooding in the United States and South Korea—and more than 1,500 people perished in the flooding in Pakistan , where resulting stagnant water and unsanitary conditions threaten even more.

The effects of climate change—and the looming threat of what’s yet to come—take a significant toll on mental health too. One 2021 study on climate anxiety, published in the journal Nature , surveyed 10,000 young people from 10 different countries. Forty-five percent of respondents said that their feelings about climate change, varying from anxiety to powerlessness to anger, impacted their daily lives.

A patient with dengue fever, a mosquito-borne disease, in Karachi, Pakistan, where the spread of diseases worsened due to flooding, September 2022

Fareed Khan/AP Photo

Worsening inequity

The climate crisis exacerbates existing inequities. Though wealthy nations, such as the United States, have emitted the lion’s share of historical greenhouse gas emissions, it’s developing countries that may lack the resources to adapt and will now bear the brunt of the climate crisis. In some cases, low-lying island nations—like many in the Pacific —may cease to exist before developed economies make meaningful reductions to their carbon emissions.

Even within wealthier nations, disparities will continue to grow between those rich enough to shield themselves from the realities of climate change and those who cannot. Those with ample resources will not be displaced from their homes by wars over food or water—at least not right away. They will have homes with cool air during heat waves and be able to easily evacuate when a hurricane is headed their way. They will be able to buy increasingly expensive food and access treatment for respiratory illness caused by wildfire smoke. Billions of others can’t—and are paying the highest price for climate pollution they did not produce.

Hurricane Katrina, for example, displaced more than one million people around the Gulf Coast. But in New Orleans , where redlining practices promoted racial and economic segregation, the city’s more affluent areas tended to be located on higher ground—and those residents were able to return and rebuild much faster than others.

Displacement

Climate change will drive displacement due to impacts like food and water scarcities, sea level rise, and economic instability. It’s already happening. The United Nations Global Compact on Refugees recognizes that “climate, environmental degradation and disasters increasingly interact with the drivers of refugee movements.” Again, communities with the fewest resources—including those facing political instability and poverty—will feel the effects first and most devastatingly.

A flood-damaged home in Queens, New York, December 1, 2021

K.C. Wilsey/FEMA

Economic impacts

According to the 2018 National Climate Assessment, unless action is taken, climate change will cost the U.S. economy as much as $500 billion per year by the end of the century. And that doesn’t even include its enormous impacts on human health . Entire local industries—from commercial fishing to tourism to husbandry—are at risk of collapsing, along with the economic support they provide.

Recovering from the destruction wrought by extreme weather like hurricanes, flash floods, and wildfires is also getting more expensive every year. In 2021, the price tag of weather disasters in the United States totaled $145 billion —the third-costliest year on record, including a number of billion-dollar weather events.

The first wave of impacts can already be felt in our communities and seen on the nightly news. The World Health Organization says that in the near future, between 2030 and 2050, climate change is expected to cause an additional 250,000 deaths per year from things like malnutrition, insect-borne diseases, and heat stress. And the World Bank estimates that climate change could displace more than 140 million people within their home countries in sub-Saharan Africa, South Asia, and Latin America by 2050.

But the degree to which the climate crisis upends our lives depends on whether global leaders decide to chart a different course. If we fail to curb greenhouse gas emissions, scientists predict a catastrophic 4.3 degrees Celsius , (or around 8 degrees Fahrenheit) of warming by the end of the century. What would a world that warm look like? Wars over water. Crowded hospitals to contend with spreading disease. Collapsed fisheries. Dead coral reefs. Even more lethal heat waves. These are just some of the impacts predicted by climate scientists .

Solar panel installation at a floating photovoltaic plant on a lake in Haltern am See, Germany, April 2022

Martin Meissner/AP Photo

Climate mitigation, or our ability to reverse climate change and undo its widespread effects, hinges on the successful enactment of policies that yield deep cuts to carbon pollution, end our dependence on dangerous fossil fuels and the deadly air pollution they generate, and prioritize the people and ecosystems on the frontlines. And these actions must be taken quickly in order to ensure a healthier present day and future. In one of its latest reports, the IPCC presented its most optimistic emissions scenario, in which the world only briefly surpasses 1.5 degrees of warming but sequestration measures cause it to dip back below by 2100. Climate adaptation , a term that refers to coping with climate impacts, is no longer optional ; it’s necessary, particularly for the world’s most vulnerable populations.

By following the urgent warnings of the IPCC and limiting warming, we may be able to avoid passing some of the critical thresholds that, once crossed, can lead to potentially irreversible, catastrophic impacts for the planet, including more warming. These thresholds are known as climate tipping points and refer to when a natural system "tips" into an entirely different state. One example would be Arctic permafrost, which stores carbon like a freezer: As the permafrost melts from warming temperatures, it releases carbon dioxide into the atmosphere.

Importantly, climate action is not a binary pass-fail test. Every fraction of a degree of warming that we prevent will reduce human suffering and death, and keep more of the planet’s natural systems intact. The good news is that a wide range of solutions exist to sharply reduce emissions, slow the pace of warming, and protect communities on the frontlines of climate impacts. Climate leaders the world over—those on major political stages as well as grassroots community activists—are offering up alternative models to systems that prioritize polluters over people. Many of these solutions are rooted in ancestral and Indigenous understandings of the natural world and have existed for millennia. Some solutions require major investments into clean, renewable energy and sustainable technologies. To be successful, climate solutions must also address intersecting crises—like poverty, racism, and gender inequality —that compound and drive the causes and impacts of the climate crisis. A combination of human ingenuity and immense political will can help us get there.

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Global warming decreases connectivity among coral populations

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Heat Waves Are Moving Slower and Staying Longer, Study Finds

Climate change is making heat waves linger for longer stretches of time, exacerbating the effects of extreme temperatures.

By Delger Erdenesanaa

When heat waves swept across large parts of the planet last summer , in many places the oppressive temperatures loitered for days or weeks at a time. As climate change warms the planet, heat waves are increasingly moving sluggishly and lasting longer, according to a study published on Friday .

Each decade between 1979 and 2020, the rate at which heat waves travel, pushed along by air circulation, slowed by about 5 miles per day, the study found. Heat waves also now last about four days longer on average.

“This really has strong impacts on public health,” said Wei Zhang, a climate scientist at Utah State University and one of the authors of the study, which appeared in the journal Science Advances.

The longer heat waves stick around in one place, the longer people are exposed to life-threatening temperatures . As workers slow down during extreme heat, so does economic productivity . Heat waves also dry out soil and vegetation, harming crops and raising the risk of wildfires.

These changes to heat wave behavior have been more noticeable since the late 1990s, Dr. Zhang said. He attributes the changes in large part to human-caused climate change, but also in part to natural climate variability.

The study is among the first to track how heat waves move through both space and time.

Rachel White, an atmospheric scientist at the University of British Columbia who wasn’t involved in the paper, said she had been waiting to see research like this.

“We know that climate change is increasing the intensity of heat waves. We know climate change is increasing the frequency of heat waves,” Dr. White said. “But this study really helps us understand more about how that’s happening.”

Dr. Zhang and his colleagues analyzed temperatures around the world between 1979 and 2020. They defined heat waves as contiguous areas reaching a total of 1 million square kilometers (247 million acres) or more, where temperatures rose to at least the 95th percentile of the local historical maximum temperature (basically, enormous blobs of unusually hot air). The heat waves also had to last for at least three days. The researchers then measured how far these giant air masses moved over time to calculate their speed.

Over all the years they studied, heat waves slowed down by about 8 kilometers per day each decade, or nearly 5 miles per day each decade.

The average life span of heat waves has also stretched out: From 2016-20, they persisted for an average of 12 days, compared with eight days from 1979 to 1983. These longer-lived heat waves are also traveling farther, increasing the distance they travel by about 226 kilometers per decade.

The researchers also found that heat waves are becoming more frequent, to an average of 98 per year between 2016 and 2020, from 75 per year between 1979 and 1983.

There are some regional differences. Heat waves are lasting longer particularly in Eurasia and North America. And they are traveling farther particularly in South America.

To examine the role of climate change, the researchers used models to simulate temperatures in scenarios with and without the warming from human greenhouse gas emissions. They found that the scenario with these emissions was the best match for what has actually happened to heat wave behavior, indicating that climate change is a major force behind these trends.

Scientists have started to detect a larger pattern of air circulation and upper atmosphere winds like the jet streams getting weaker, at least during the summer at higher latitudes in the Northern Hemisphere. This could cause extreme weather events of all kinds to stall and overstay their welcome.

“It stands to reason that that would slow down the speed of heat waves,” said Stephen Vavrus, the state climatologist for Wisconsin. Dr. Vavrus studies atmospheric circulation but wasn’t involved in this research.

The new study did find a correlation between a weaker jet stream and slower heat waves. Dr. White, however, thinks more research is needed to determine whether the jet stream is truly the cause.

No matter the exact reasons for the slowdown, the harmful effects remain.

“It’s sort of multiple factors conspiring together,” Dr. Vavrus said. If heat waves become more frequent, more intense, last longer and cover a greater area, he said, “that really increases the concern we have for their impacts.”

Dr. Zhang is especially concerned about cities, which are often hotter than their surrounding areas because of the urban heat island effect . “If those heat waves last in the city for much longer than before, that would cause a very dangerous situation,” he said.

Alongside his atmospheric research, Dr. Zhang is helping with local efforts to plant more trees and grasses around bus stops in Salt Lake City, where people have to wait in the sun during increasingly hot summers. He suggested that cities build more cooling centers, especially for people experiencing homelessness.

“There are some things a community can do,” he said.

While waiting for international leaders to make progress on cutting greenhouse gas emissions and stopping climate change, Dr. Zhang said, local adaptation efforts are important to help keep people safer.

Delger Erdenesanaa is a reporter covering climate and the environment and a member of the 2023-24 Times Fellowship class, a program for journalists early in their careers. More about Delger Erdenesanaa

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Who are today’s climate activists? Dispelling 3 big myths for Earth Month

Director of the Center for Environment, Community & Equity and Professor in the School of International Service, American University

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Dana R. Fisher receives funding from the MacArthur Foundation and the William and Flora Hewlett Foundation. She is a non-resident Senior Fellow at the Brookings Institution.

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As Earth Month 2024 gets underway, climate activists around the world are planning rallies and other events over the coming weeks to draw attention to the growing threats posed by climate change.

Many of these demonstrations will focus on what humanity can do to stop fueling the damage. But while activists are amplifying the dire findings from scientists, you’ll likely see fossil fuel supporters attacking them on social media and TV.

It’s easy to get caught up in the myths about climate activism, particularly in today’s polarized political environment. So, let’s take a moment to explore the truth about three of the big myths being told about climate activism and the climate movement today.

Myth 1: Climate activists are just young people

The media tends to focus most of its attention on young people in the climate movement, including those inspired by Greta Thunberg’s school strikes for climate, the international Fridays for Future , or the Sunrise Movement , which focuses on U.S. climate action.

Nevertheless, a substantial proportion of the active climate movement today is made up of older adults, including those called “ climate grannies ” and the “ rocking chair rebellion .”

Just as young people have outspoken climate leaders, many of these older activists were inspired to get involved by longtime activists such as Jane Fonda and Bill McKibben and the group McKibben started specifically to mobilize older Americans: ThirdAct . As my research has found , these more mature activists cut their teeth in the civil rights and anti-war movements, along with earlier waves of the environmental movement.

Over the past 25 years, I have surveyed numerous waves of activists participating in demonstrations and protests to understand who they are and what motivates them to participate in activism . My new book, “ Saving Ourselves: From Climate Shocks to Climate Action, ” brings these findings together to understand how the climate movement has evolved along with the climate crisis.

When I surveyed participants at the March to End Fossil Fuels , which drew 75,000 people in New York City in September 2023, a quarter of the crowd was 53 years old or older. At a much smaller demonstration that targeted the White House Correspondents’ Association dinner in April 2023, I found the average age of the activists was 52, and a quarter of them were 69 or older .

Myth 2: Climate activists mostly do things like throw soup and disrupt events

While the activists engaging in civil disobedience, such as throwing soup on famous paintings or disrupting sports events , get the lion’s share of the media attention, the climate movement includes a wide spectrum of environmentally concerned activists using a broad range of tactics.

Activists are actively working to get climate-concerned candidates elected , pressure corporations to cut their emissions, encourage schools and municipalities to transition to electric buses , and make front-line communities more resilient to climate shocks , among many other efforts to slow climate change.

Many activists are involved with established organizations, such as 350.org , the Environmental Defense Fund and the Citizens’ Climate Lobby . Their numbers – EDF alone claims 3 million supporters – and financial strength can give them a powerful voice .

Others participate in less formal groups that make up the radical flank, such as Extinction Rebellion and Climate Defiance . Although these factions of the movement do not necessarily agree on the path to social change, they share the same mission: to end the climate crisis.

Myth 3: Confrontational climate activism doesn’t work

In recent months, protesters have thrown soup at the Mona Lisa , dumped pink powder on the U.S. Constitution and disrupted a Broadway show , among other events. These confrontational actions are not generally popular, but neither were the radical tactics of earlier social movements.

In 1961, 61% of the U.S. population disapproved of the Freedom Riders , who rode interstate buses into the South to challenge segregation. And 57% thought that sit-ins at lunch counters and other locations where Black Americans were refused service hurt the Civil Rights Movement. In hindsight, research has shown how essential those efforts were to the success of the Civil Rights Movement.

Nonviolent civil disobedience in the climate movement also plays an important role in keeping climate change in the media and on people’s minds.

Even though the radical flank of the climate movement is not particularly popular with the general public, there is no evidence that it is turning off other activists in the movement. In fact, there is reason to believe that confrontational acts can help mobilize sympathizers to support more moderate efforts of the climate movement.

When I asked participants at the 2023 March to End Fossil Fuels if they supported climate groups doing nonviolent civil disobedience, not one of the respondents reported disapproving of these groups and their actions.

The impact of these activists’ efforts goes well beyond media coverage, too. For example, when President Joe Biden announced his decision to pause approvals of liquefied natural gas exports in January 2024, he mentioned climate activists : “We will heed the calls of young people and frontline communities who are using their voices to demand action from those with the power to act.”

Myths about climate change are often spread to try to slow efforts to deal with climate change and are often funded by fossil fuel interests .

But that isn’t stopping climate activists, who, like the rest of the world, are experiencing climate change and feel a responsibility to speak out.

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A Systematic Literature Review of the Impact of Climate Change on the Global Demand for Psychiatric Services

Julia feriato corvetto.

1 Heidelberg Institute of Global Health (HIGH), Heidelberg University Hospital, Heidelberg University, 69120 Heidelberg, Germany

Ammir Yacoub Helou

2 Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, São Paulo 05508-900, Brazil

Peter Dambach

Thomas müller.

3 Private Clinic Meiringen, 3860 Meiringen, Switzerland

4 Translational Research Center, University Hospital of Psychiatry and Psychotherapy, University of Bern, 3000 Bern, Switzerland

Rainer Sauerborn

Associated data.

Not applicable.

Climate Change (CC) imposes important global health risks, including on mental health (MH). They are related mostly to psychological suffering caused by climate-related events and to the heat-vulnerability caused by psychiatric disorders. This growing burden may press MH services worldwide, increasing demand on public and private systems in low-, middle-, and high-income countries. According to PRISMA, two independent reviewers searched four databases for papers published before May 2022 that associated climate-related events with healthcare demand for psychiatric conditions. Of the 7432 papers retrieved, we included 105. Only 29 were carried out in low- and middle-income countries. Twelve related the admission numbers to (i) extreme events, while 93 to (ii) meteorological factors—mostly heat. Emergency visits and hospitalizations were significantly higher during hot periods for MH disorders, especially until lag 5–7. Extreme events also caused more consultations. Suicide (completed or attempted), substance misuse, schizophrenia, mood, organic and neurotic disorders, and mortality were strongly affected by CC. This high healthcare demand is evidence of the burden patients may undergo. In addition, public and private services may face a shortage of financial and human resources. Finally, the increased use of healthcare facilities, in turn, intensifies greenhouse gas emissions, representing a self-enforcing cycle for CC. Further research is needed to better clarify how extreme events affect MH services and, in addition, if services in low- and middle-income countries are more intensely demanded by CC, as compared to richer countries.

1. Introduction

Climate is changing drastically and unprecedentedly [ 1 , 2 , 3 ]. Recently, the eight consecutive years from 2015 until 2022 were considered the warmest years since the beginning of temperature measurement [ 4 , 5 ]. Concomitantly, extreme events have become more visible and deadly [ 6 ]. Still, this threatening scenario tends to be aggravated, considering that only few countries have met their Nationally Determined Contributions (NDCs) so far, and that greenhouse gas emissions (GHG) continue to grow every year [ 7 , 8 ].

This wide range of climate change-sensitive variables—weather components potentially worsened by climate change (CC)—imposes consequences on human health. They were extensively explored during the past decades by the intersection between environmental and health research, but in contrast to the somatic medical conditions, much less is known about the mental health (MH) impacts of CC. Based on Verner et al. (2016), the Figure S1 and Table S1 in Supplementary Materials displays the publication numbers from the main health domains and compares them to how mental health received late scientific attention, in the context of CC [ 9 ].

The available literature could already indicate how CC can interfere on MH, as well [ 10 ]. In this scenario, there are specific reasons why MH patients are in a vulnerable condition. The main contributors are the heat intolerance created by the disorders, pre-existing social and economic vulnerability, and psychotropic drugs used as treatment [ 10 , 11 , 12 , 13 ].

This burden may be still intensified, due to the high rates of psychiatric disorders worldwide. Since 2005, there has been a growth of approximately 15% of the prevalence of common mental diseases, and, among youth, they occupy the leading cause of health afflictions in the United States [ 14 , 15 ]. The incidence during lifetime can reach levels up to 50% of the population, depending on the country [ 16 ]. Finally, once it is diagnosed, the condition imposes an important disability on the patient [ 17 ].

This health disturbance can be reflected in the overload of health systems worldwide, increasing costs for both public and private sources [ 18 , 19 ]. This acute effect can be measured through different methods. In a country where healthcare is effectively delivered, service utilization—emergency department visits, hospitalization, scheduled outpatients—is usually considered the most accurate method for acute needs, as it has the potential sensitivity for fluctuation according to external situations [ 20 ].

Contrarily, what happens in low- and middle-income countries is that the funding for mental illness care does not reflect the real need and corresponds to a median spending of less than 1% of their health budget [ 19 , 21 , 22 , 23 ]. Human resources are also scarce, and, commonly, there is only one psychiatrist responsible for thousands of patients [ 24 ]. In this case, the admission numbers, despite still being the best possible measurement, are probably fewer than anticipated, when compared to an ideal scenario. In both described cases, high- or low- and middle-income countries, the psychiatric health demand will gradually continue to pressure the systems, considering that CC tends to intensify and create new climate-related events [ 2 , 10 ].

Therefore, from a public health perspective, it is important to differentiate and focus on conditions that are potentially long-lasting or overwhelming for the collective. In addition, the recent terms ‘climate change distress’, ‘eco-anxiety’, and ‘solastalgia’ are terms used to describe the uncertainty and fear produced by CC, and they were found by Charlson et al. (2021) [ 25 ] to be among the most prevalent outcomes measured by the studies, even though they are often considered limited conditions [ 26 ]. By using health services as the final measure, we tend to delineate these conditions and then be more objective about the long-term burden.

One similar review, which also analyses mental health services demand, was recently conducted in Australia, with specific focus on heatwaves. The authors—Mason and Colleagues, 2022 [ 27 ]—indicate that such evidence is important to increase preparedness of health systems across the country, in order to supply and balance the demand of warmer-than-average periods.

Therefore, the purpose of this review is:

• To investigate the demand for mental health services caused by CC worldwide—hospital admissions (HA), emergency department visits (EDV), outpatient consultations, and ambulance dispatch—due to psychiatric symptoms, disorders, or mortality.
• To identify which of these disorders are responsible for the consultations, in the aftermath of CC variables.
• To compare health services use in low- and middle-income countries to that in high-income countries and examine how these populations are undertreated for having less access to healthcare services.

To the best of our knowledge, this is the first systematic literature review to focus on the effective health system burden correlated to CC and psychiatry.

2. Materials and Methods

This systematic literature review was conducted in accordance with the PRISMA guidelines (Preferred Reporting Items for Systematic reviews and Meta-Analyses) [ 28 ] and registered in PROSPERO (2022, CRD42022353023) [ 29 ].

Papers were retrieved using the applied search terms on the databases PubMed, Embase, Web of Science, and PsycInfo, which were published until 10 May 2022, without date limit.

The keywords from two categories were combined in the following search terms, using Boolean operators (detailed search terms and Boolean operators can be found in Supplementary Materials—Table S2 ): climate change, global warming, heatwave, hot temperature, natural disaster, psychiatric disorder, mental disorder, suicide, suicide attempt, depression, mania, schizophrenia, dementia, substance abuse, bipolar disorder, psychosis, organic disorder, anxiety disorder, neurotic disorder, neurocognitive disorder, and, lastly, post-traumatic stress disorder.

These psychiatric disorders were previously related to being susceptible to CC [ 10 , 25 , 30 ]. The search words are either MeSH terms or specific disease names listed on the International Classification of Diseases—10th revision (ICD-10th) ( Supplementary Materials—Figure S2 ) [ 31 ].

The CC variables were considered to be all the possible components that can be potentially influenced or worsened by CC: meteorological factors (mostly heat) and extreme events [ 2 ]. In this context, air pollution was not included in this review, since it is considered to be one of the causes of CC, instead of a consequence of it. Still, ‘hot temperature’, ‘heat’, or ‘warmer than average’ were temperature values above a certain threshold specified by the author ( Supplementary Materials—Table S3 ).

2.1. Studies Selection and Quality Assessment

In the first phase, during the title and abstract selection, the papers were kept if selected by at least one of the two independent readers (J.C. and A.H.), through the online selecting tool for systematic reviews Rayyan [ 32 ]. Then, the selected papers were full text reviewed according to the inclusion and exclusion criteria. In the full text selection, both readers agreed on its inclusion, otherwise a third independent reader was required to decide. Detailed inclusion and exclusion criteria can be found in Table 1 .

Eligibility criteria: inclusion and exclusion criteria for the selection of papers.

Studies that did not explicitly analyze the impact of CC variables on health services demand due to psychiatric causes (symptoms, disorders, or mortality) were excluded.

Before data appraisal, the ‘quality assessment tool for Observational Cohort and Cross-Sectional Studies’ or ‘for Case-Control studies’, depending on the design of the analyzed study, of the National Institute of Health (NIH) was used by the two reviewers, also independently, to determine the final eligibility for the included papers ( Supplementary Materials—Table S4 ) [ 33 ]. Studies were assessed as either ‘poor’, ‘fair’, or ‘good’. The ‘poor’ quality studies were excluded. In case only one of the reviewers rated the study as ‘poor’, a third independent reader was required again. Otherwise, if the two assessments were considered at least ‘fair’, the study was included. Each question from the NIH questionnaires received 1 score. In case a study achieved less than 50% of the maximum score, it was considered ‘poor’. Between 50% and 74% were placed in the ‘fair’ category, and, finally, the ‘good’ were the ones that scored 75% or more.

2.2. Data Appraisal

Given the two different mechanisms by which CC may affect MH, the studies were distributed in the following major groups for data appraisal: (i) extreme events and (ii) meteorological variables. Even though a heatwave is considered an extreme event, it was placed in the last group (ii), together with hot temperature, since both act through the same mechanism on MH patients. In each of the groups, the corresponding diseases’ classification followed the ICD—10th revision.

First, the subgroup called ‘MH in general’ comprises the unclassified outcomes, in which the authors represented all of the psychiatric conditions. Secondly, the specific outcomes were grouped as follows: organic disorders (F00–F09), substance misuse (F10–F19), schizophrenia (F20–F29), mood disorders (F30–F39), neurotic disorders (F40–F48), behavioral disorders (F50–F59), personality disorders (F60–F69), intellectual disabilities (F70–F79), specific developmental disorders (F80–F89), and behavioral and emotional disorders with onset usually in childhood (F90–F99) (ICD–10th detailed in Supplementary Materials—Figure S2 ). Still, suicide attempts or completed suicides were also listed separately. The last classification was called ‘mortality’, and corresponded the cases of death linked, by the authors, to a MH cause.

In case papers addressed multiple human disorders, the only retrieved data was the one corresponding to MH.

We performed an extensive literature review and could rely on a relatively large number of studies ( n = 105). The vast majority of the studies here comprised were ‘fair’ in quality ( n = 91), and only 1 was graded as ‘poor’ and, therefore, excluded from the analysis. Still, 14 papers were rated as ‘good’.

From the 7432 papers searched via four databases (PubMed = 1183, PsycInfo = 752, Embase = 2286, and Web of Science n = 3211), we included 105 for data extraction ( Figure 1 ). The general information from included studies can be found in Table 2 , including the number of each type of health service that was approached. A more detailed table is included in the Supplementary Material (Table S4) . The CC variables were found to be predominantly heat and heatwaves ( n = 92; 87.6%). Only one study reported other meteorological exposures, snow and rain, which they reported to be associated with CC. Few articles ( n = 12; 11.4%) studied the influences of extreme events on psychiatry.

PRISMA diagram for Systematic Literature Reviews [ 28 ].

General characteristics of all the included studies. * Weather variables included: snow and rain, temperature variability, temperature change between neighboring days, and daily excess hourly heat. The order studies were placed in the table was, as follows: MH in general or multiple types of disorders and, then, the sequence of specific ICD-10th, from F00 to F99. Mortality and suicide were placed next. Lastly, the extreme event-related outcomes.

The Figure 2 displays the number of included articles according to the year of publication. This review found, as expected and previously discussed, an increase in publication numbers, especially after 2016. Until May 2022, a total of 12 studies had already been published and are included here, following the positive trend.

Included studies according to the year of publication.

Twenty-nine studies (27.5%) were carried out in low- and middle-income countries. China contributed the most, with 19 publications. Figure 3 displays how the studies are spread in the world, evidencing the central role of high-income countries.

Global distribution of studies. Note: white color corresponds to missing studies in that country. Created with: paintmaps.com, accessed on 10 October 2022.

Hospital admission ( n = 34) and completed suicide ( n = 34) were found to be the most studied types of services. Even though suicide is not a service per se, it certainly requires specific sectors of the health system to be addressed. Emergency department visit was, as well, often studied ( n = 20), followed by mortality ( n = 15). Together, phone calls, ambulance dispatch, outpatient visits, and other types of provided healthcare were poorly researched ( n = 10) and could, in the future, receive more focus from science. In addition, no significant difference among them was found, and it seems that healthcare services are equally demanded. Figure 4 lists the measure of effect and displays them according to the used service.

Forest plot of significant results (relative risk), divided by type of demanded service. The numbers on the y -axis represent the study references. Abbreviations: AD: ambulance dispatch; EDV: emergency department visit. RR * represents the respective RR upper limits.

3.1. Extreme Events (n = 12)

Twelve papers ( n = 12; 11.4%) correlate CC-related extreme events with psychiatric consultations. The significant results are presented in the following Table 3 , considering a confidence interval of 95%. They are divided by type of service used and by the MH condition. In addition, the disasters responsible for the results can be found after each confidence interval. It is important to point out that the authors often presented a great range of results, given the different lags approached. Therefore, the results displayed in Table 3 represent the highest impact found by each of them, positive or negative.

Extreme events.

Main results, divided by type of service used and, still, by the MH condition that was demanded. Results presented in red are the significant negative associations. * Statistically significant result (CI 95%). Abbreviations: EDV—emergency department visit, HA—hospital admission, RR—relative risk, IRR—incidence rate ratio.

The disasters were hurricane ( n = 4), drought or dry weather ( n = 3), floods ( n = 4), extreme precipitation or extreme wet weather ( n = 2), bushfire ( n = 1), earthquake ( n = 1), severe winter weather or ice storm ( n = 2), dust storm ( n = 1), tornado ( n = 1), and severe storms ( n = 1).

In the aftermath of these extreme events, the most strongly affected MH conditions were suicide, mood—which includes Major Depressive Disorder—and neurotic disorders (anxiety, post-traumatic stress disorder, etc.). Therefore, these are the main responsible causes for the acute health service demand, showed by the studies. Substance misuse, schizophrenia and behavioral disorder were approached by fewer studies, but also showed to demand medical care.

The detailed results are described below (i–vi). They were divided in ICD-10th groups and placed according to the strength of evidence.

• (i) Suicide behavior ( n = 9)

Suicide behavior (attempt or completed suicide) showed the most consistent increase after CC-related extreme events among all studies. From the nine articles, only one showed no statistically significant increment on suicide [ 136 ].

Also, when compared to other MH conditions, suicide showed the highest risk ratio for EDV immediately after the disaster (1.68 *, 1.54–1.82), and the risk continued to rise during the whole period of study, until three years later [ 126 ].

One study found a relative increase of suicide behavior only during extreme wet weather (18.7% *, 6.2–31.2) and not during the dry [ 133 ]. In addition, farmers were particularly searched: one paper showed relative risk of 1.15 * (1.08–1.22) in male farmers when drought intensified [ 135 ]. In contrast to males, the risk for female farmers was significantly reduced [ 135 ]. In another study, the general population showed a RR of 4.23 * (1.28–13.93) due to moderate drought [ 134 ].

Lastly, it was reported that extreme large events increased the incidence of suicide, but in case of less damaging ones, the incidence decreased in the aftermath [ 131 ].

• (ii) Mood disorders ( n = 4)

The four papers found significant increase on mental health services demand for mood disorders. One showed a risk ratio for EDV of 1.59 * (1.39–1.80) right after the disaster, but it rapidly declined. On the other hand, HA appeared significantly higher one year later and, after three years, the risk ratio of hospitalization was still 1.67 * (1.47–1.87) [ 126 ].

Also, Major Depressive Disorder (MDD) was the only subtype analyzed. One study showed an incidence rate ratio of 2.57 * (1.60–4.14) of MDD in psychological services [ 126 ]. The two others pointed an increase in service use varying from 44% [ 15 ] to 245% [ 129 ]. MDD imposed a greater chance of medical need when compared also to anxiety disorders (see next section).

• (iii) Neurotic disorders ( n = 4)

All of the studies that analyzed anxiety disorders ( n = 4) found a positive correlation, showing an important increase in health services demand. One found 267 and 307% increase in incidence for elderly and non-elderly, respectively [ 129 ], while another one found an incidence rate ratio of psychological services of 2.06 * (1.21–3.49) [ 126 ]. One paper showed that EDV were not significant or even reduced until three years after a disaster, but contrarily, HA increased during most of the period, and two years later the relative risk was 1.15 (1.11–1.20) [ 126 ].

Adjustment disorder was not consistent. One study did not find any increase both for EDV and HA [ 126 ]. In opposition, two others pointed 62% more Medicaid use [ 15 ] and 160–200% incidence in health centres [ 129 ]. Only one paper studied post-traumatic stress disorder (PTSD) specifically, and the incidence for non-elderly in health services was 350% higher [ 129 ].

• (iv) Substance misuse ( n = 2)

For elderly, the risk ratio for EDV due to substance misuse was the second highest, only lower than suicide behavior. Immediately after the disaster, the risk ratio was 1.44 * (1.23–1.65), reduced after three months, but increased again, maintaining high levels until three years after the extreme event (1.19 *, 1.11–1.26). Hospitalizations appeared three months 1.12 * (1.04–1.21) and were significant until one year, then, reducing again [ 126 ]. One studied that analyzed Medicaid services in the USA showed 66% increase in services use, when comparing the numbers before and after an important flood [ 15 ].

• (v) Schizophrenia ( n = 1)

Schizophrenia (HA) was correlated with extreme precipitation. The result was positive for both urban and rural areas. The relative risk increased already at lag1 (1.056 *, 1.003–1.110), peaked at lag8 (1.072 *, 1.033–1.113), and remained significant until lag17 (1.039 *, 1.004–1.075). The fraction of HA attributable to extreme precipitation was 3.42% * (2.40–4.06). Still, this number was higher for men aged less than 39 years old [ 127 ].

• (vi) Behavioral disorders ( n = 1)

Health services in general received a higher incidence of 318 and 356% for non-elderly and elderly, respectively, due to insomnia (behavioral disorder) [ 127 ].

3.2. Meteorological Factors (n = 93)

Temperature was by far the most approached measure ( n = 92; 86.6%) and, therefore, it will be our focus on this section ( Figure 5 ). The ‘warmer than average’ factor was usually reported as high percentiles in relation to the threshold ( Supplementary Materials—Table S3 ). Heatwave (HW) was also commonly analyzed ( n = 18; 17.1%). Different definitions of HW were used, varying in terms of intensity (temperature) and duration. Five studies opted for the ‘diurnal temperature range’, whose definition is the numerical difference between the highest and lowest temperature values in 24 h. Other temperature-related factors were temperature variability, temperature change between neighboring days, daily excess hourly heat, and irregular daily variation. Finally, one study analyzed only snow and rain—among the CC sensitive variables [ 81 ], and another one included rainfall in the analysis [ 84 ].

Proportion of meteorological factors used by the authors. ‘Warmer than average’ was usually reported by the authors as high percentiles in relation to a threshold. * Other temperature variables: temperature variability (TV), temperature change between neighboring days (TCN), daily excess hourly heat (DEHH), irregular daily variation.

The most strongly affected specific MH conditions were suicide behavior; schizophrenia; substance misuse; organic, mood and neurotic disorders; and, lastly, mortality. The Figure 6 shows the proportion of significant findings, divided by disease subgroups, considering a confidence interval of 95%.

Heat and MH according to the percentage of studies found to be statistically significant (CI 95%).

The majority of studies found significant and positive evidence that MH diseases in general increased the risk for health service need, due to hot weather. The most studied services were HA, EDV, suicide, and mortality. One study [ 34 ] found that approximately 14% of all the emergency admission numbers for mental disorders were attributable to hot temperatures. The delayed or lagged effects showed an increase, according to different studies, until 5 days (RR 1.43 *) [ 46 ], 7 days (RR 1.28 *) [ 51 ], 11 days (RR 1.84 *) [ 54 ] and 14 days (Percent change in risk of 22% *) [ 60 ]. Likewise, the same-day effect was significant: RR 1.158 * for EDV [ 34 ] and 1.229 * for HA [ 52 ].

A longer HW (7 days) imposed a higher risk (RR 1.36 *) of HA than a 3-day (RR 1.15 *) and a 1-day HW (RR 1.04 *) [ 38 ]. According to one other study [ 59 ], HW intensity seemed to cause an even higher risk—62% (RR 1.62 *)—of hospitalization.

A study in China, during heatwave periods, pointed to important subgroups that were at higher risk of MH care need: residents of urban areas (OR 1.523 *, 1.233–2.349), outdoor workers (OR 1.714 *, 1.198–2.398), and single patients (OR 1.709 *, 1.233–2.349) [ 47 ].

Mortality was approached in thirteen studies, and eleven of them presented evidence on how MH is a risk factor for dying on hot days. A 1 °C increment in temperature increased the odds of dying in the general population and in MH patients by 1.9% (OR 1.019 *) and 5.5% (OR 1.055 *), respectively [ 88 ]. HW were often explored, and the percent change in cause was 29.7% * [ 95 ]. Four studies pointed out that elderly patients were more vulnerable [ 34 , 35 , 38 , 92 ]. One study found that poverty enhanced the risk of mortality during hot days [ 86 ].

Finally, Table 4 displays the main results. The significant numbers can be linked to which type of service was demanded and due to in which disorder group this demand took place.

Meteorological factors.

Main results, divided by type of service used and, still, by the MH condition that was demanded. * Statistically significant result (CI 95%). Abbreviations: EDV—emergency department visit, HA—hospital admission, RR—relative risk, IRR—incidence risk ratio, OR—odds ratio, RMR—relative mortality ratio.

Despite being included in the analysis, disorders of adult personality ( n = 5) were not found to be related to heat. Behavioral disorders ( n = 6) showed no consistent result, and five out of the six studies found no relationship between those variables, while one could point a positive correlation between temperature (PET) and admission numbers [ 49 ]. Additionally, only one study found that mental retardation ( n = 4) was affected by HW [ 38 ].

• (i) Suicide behavior ( n = 33)

Suicide was the most studied outcome, and approximately 94% of the papers ( n = 31) found a statistically significant relationship between temperature and suicide behavior: attempted or completed. Exceptionally, two of them evidenced a reduced risk of suicide during extreme hot temperatures, with a RR of 0.97 * (0.95—0.99) [ 90 ] and average decrease (according to the authors) of IRR 0.94 * between male and females [ 97 ], while the others pointed that heat increased suicide behavior. Studies showed a large range of significance: from IRR 1.06 * (1.01–1.12) [ 37 ] to RR 1.35 * [ 111 ]. Females had a higher risk, according to one study [ 102 ].

Heat increased violent suicide attempts and completed suicide, but not the non-violent behaviors in three studies [ 104 , 116 , 117 ]. One other study showed evidence that both methods were significantly higher, but still pointed out that the temperature threshold associated with increasing violent methods was lower (30.3 °C) than the temperature needed to significantly increase non-violent suicides (32.7 °C) [ 103 ].

Ambulance dispatch was measured by one study, during different intensities of heatwave, and the RR was found to be relatively high, varying from 3.70 * (1.00–13.66) to 4.53 * (1.23–16.68) depending on the HW intensity [ 115 ]. Another ambulance dispatch-based study showed a lower, but still positive, number: RR 1.11 * (1.07–1.15) [ 98 ].

Still, one study showed the indirect effect of temperature (increment of 1 °C) on a 3.6% decline of agricultural productivity, leading to a 4.8% increase in risk of suicide among farmers [ 108 ].

• (ii) Schizophrenia ( n = 24)

Seventeen studies (65.38%) found positive and significant results, showing these patients are more vulnerable to heat and, therefore, have a higher chance of needing healthcare services. Two studies presented both same-day and cumulative risk assessments. They found a higher risk when the heat was sustained up to seven or eight days (RR 2.49 *, 1.69–3.69 and 1.37 *, 1.168–1.614), while one-day heat distress brought relatively less risk: RR 1.10 * (1.03–1.17) and 1.06 * (1.019–1.106), respectively [ 45 , 71 ]. To mortality, schizophrenia was not significantly related.

In addition, it seems, from another study, that the heat intensity of a HW brings more risk than its duration, with a RR of 1.50 * (1.20–1.86) and RR:1.14 * (1.01–1.30), respectively [ 59 ].

Finally, there is also evidence that large temperature variation within the day (maximum minus minimum T) may increase hospital admission up to 22% (RR 1.22 *, 1.08–1.37) [ 76 ].

• (iii) Mood disorders ( n = 23)

Sixty-two percent of the papers ( n = 15) presented evidence of the influence of temperature on outpatient appointments (OR 1.32 *, 1.08–1.62) [ 36 ], emergency department visits (IRR 1.07 *, 1.05–1.09; RR 1.05 *, 1.01–1.09; and RR 1.33 *, 1.03–1.71) [ 37 , 39 , 51 ], and hospitalization (RR 1.34 *, 1.05–1.71) [ 35 ]. One showed that rainfall has negative effect on mania [ 84 ].

From the six studies that specifically researched bipolar disorder or mania, four of them found positive correlations with an increase in healthcare demand [ 80 , 81 , 82 , 83 ], while two did not present significant results [ 84 , 85 ].

Depression, another type of mood disorder, was not found to be at significantly higher risk from HA, according to one paper [ 83 ]. Contrarily, long-term exposure to higher temperatures (residing in areas with average temperatures above 23 °C) increased the risk by 7% of developing MDD per 1 °C of increment (hazard ratio 1.07 *, 1.02–1.12) [ 79 ].

• (iv) Organic disorders ( n = 17)

Thirteen of the studies (76.47%) that analyzed organic disorders found a positive association between temperature and medical needs or even death. Patients with organic disorders had 31% more risk of being admitted to an emergency department [ 51 ] and an odds ratio of 8.33 * of being hospitalized [ 68 ]. The risk of mortality was 3% higher [ 11 ].

Alzheimer’s disease was specifically studied and showed a significant RR of 1.30 * (1.12–1.52) [ 65 ] for hospital admission and an increase in RR of 269% * (76–665%) [ 66 ] for mortality.

• (v) Substance misuse ( n = 16)

Twelve papers (70.58%) presented statistically significant association between temperature and HA or EDV, where the RR varied from 1.13 * (1.00, 1.27) for hospitalization [ 35 ] and 1.30 * (1.18–1.42) for emergency visits [ 51 ]. For intense HW, the RR was even higher, displaying 221% * higher risk of hospitalization [ 59 ].

Phone calls requiring healthcare for substance misuse were also measured: the RR was 1.08 * (1.03–1.14) [ 63 ], and the risk of death increased 8% in patients diagnosed with alcohol misuse. In those who had used other substances (excluding alcohol), the risk increased to 20% [ 11 ].

• (vi) Neurotic and anxiety disorders ( n = 14)

Eleven out of fourteen studies (78.57%) pointed out that neurotic disorders influenced healthcare demand due to hot temperatures. HA did not appear to be influenced [ 35 ], but for EDV, the RR varied from 1.05 * (1.002–1.099) [ 46 ] to 1.27 * (1.19–1.36) [ 51 ].

The odds that patients scheduled a medical appointment after a cumulative heat exposure was 30% higher (OR 1.30 *, 1.08–1.58) even at lag 9, suggesting that not-emergency services, such as scheduled appointments, may receive a delayed demand [ 36 ].

• (vii) Behavioral and emotional disorders with onset during childhood/adolescence ( n = 4)

Two of the studies pointed a higher risk of healthcare need, with an IRR of 1.11 * (1.05–1.18) for EDV [ 37 ] and RR 1.29 * (1.09–1.54) [ 55 ] for HA. A third study, in contrast, reported an important reduction of the number of emergency room visits after a heatwave: IRR 0.578 * (0.349–0.955) [ 42 ].

• (viii) Disorders of psychological development ( n = 2)

The autism spectrum disorders were found to cause additional susceptibility to heat and, therefore, demand emergency department visits (IRR 1.64 *, 1.086–2.480) [ 42 ] and hospital admissions (RR 1.29 *, 1.09–1.54) [ 55 ], with relatively elevated risk.

4. Discussion

The findings from the 105 studies pointed to a high probability, according to strong evidence, that more consultations will be necessary in public and private systems. We could not find any evidence supporting that the distinct types of health services are differently affected. Still, ambulance dispatch, telephone calls, and outpatient visits were seldomly measured and need to be better addressed in the future, but were, likewise, positively associated with CC variables. Completed suicide and mortality were strongly affected. Even though these two conditions do not require common consultations at health facilities, they do demand other sources of assistance to be carried out.

We identified that elderly people—above 60 years of age—were among the most vulnerable group for both extreme events and meteorological conditions [ 35 , 38 ]. Poverty was found to enhance the risk of heat-related death, while male farmers were particularly at risk due to extreme events. Residents of urban areas, outdoor workers, and single patients were also reported to be at higher risk [ 47 ]. The increase in health service demand was most significant until a lag 5–7 [ 45 , 46 ], but some studies show the effect up to 14 [ 60 ], 21 [ 41 ] and even 30 days [ 45 ].

We also found that a great range of psychiatric disorders, mostly from F50 to F99, were not properly approached, and that the scientific evidence for them is still poor. Even though these conditions are less prevalent at healthcare facilities, future attention and research on the topic are needed.

One specific disease that received less attention than expected was post-traumatic stress disorder (PTSD). Despite being broadly discussed, only one study focused objectively on if PTSD demands healthcare after an extreme event (129). This important gap of knowledge should be addressed in the future, as well.

The lack of extreme event-related studies that addressed specifically health services use was another identified gap in the scientific evidence. Most of the studies about extreme events measured the distress over the affected population through questionnaires in the communities, instead of through health assistance needs. These methodologies were removed from this review, because even though they corroborate the important mental distress these people go through, they do not necessarily reflect long-lasting suffering and more consultations in health systems. As found by Lai et al. (2021) [ 26 ], most of the symptoms in the direct aftermath will not become chronic and burdening diseases. Therefore, it is likely they do not demand intense healthcare after all.

When comparing the consultation rates in low-, middle- and high-income countries, we did not identify any significant difference, meaning that the increase rate was similar among them. We hypothesized that, given the higher vulnerabilities present in poorer countries, the numbers found would possibly be larger if their health systems were adequately prepared to receive more patients. For a proper comparison, more studies addressing healthcare use in poorer countries are needed.

Few studies found negative associations linking CC to healthcare use [ 90 , 97 , 126 ]. Begum et al. (2022) linked Hurricane Sandy to less EDV for anxiety. Contrarily though, for HA, the same article reported a significant increase. We hypothesize that the so called ‘harvesting effect’ may be responsible for a forward shift in one category of healthcare visits, inducing a consequent reduction in the others.

This increase in health demand will likely overwhelm health systems and pressure costs of healthcare. As an example, one article using Medicaid data pointed out 8–10% more costs after a flood [ 19 ], especially as extreme events become more frequent and temperatures rise even more. According to the United Nations Office for Disaster Risk Reduction, there were 389 climate-related events in 2020, a number above the previous annual average (368). In addition, one of the latest available reports shows a probable increase in temperatures of 2.4 °C by 2100, provided that all countries implement their nationally determined contributions (NCD) [ 137 , 138 ].

In addition to the financial costs, this acute increase in demand can create an emergency situation in health facilities, with shortage of drugs, beds, human services, and other basic resources. In a much bigger proportion, this emergency picture happened during the coronavirus pandemic, mostly in less prepared regions.

Furthermore, the carbon footprint released from the healthcare services is, already nowadays, one of the biggest contributors of CC [ 139 ]. The data we report here corroborate that these services will be more intensively utilized, leading to a self-reinforcement cycle that promotes proportionally greater greenhouse gas emissions into the atmosphere.

Some characteristics of mental health patients—directly or externally related to the disorder—may lead to this higher healthcare demand. The responsible mechanisms for that are important to be delineated. The aim is to point out a pathway to policymakers and medical professionals where policies could effectively act, avoiding consultations for development of a new disorder, for disease exacerbation, heat-related disorders, suicide attempts, and, still, prevent mortality.

Firstly, climate-related events frequently cause mental suffering. These circumstances may lead to punctual and self-limited mental distress or to a chronic disorder [ 10 , 19 ]. In general, the two possible scenarios are determined by a community’s pre-existing vulnerability and by the adaptation and recovery power delivered through public policies [ 140 ].

Furthermore, heat-related vulnerability is promoted by some psychiatric disorders through inadequate heat dissipation, which facilitates a dangerous state of hyperthermia in the body [ 141 ]. Still, additional heat intolerance is caused by the use of certain psychotropic medications—antipsychotics, antiparkinsonians, hypnotics, anxiolytics, and opiates [ 12 , 13 , 117 ]. A further mechanism is related to disease exacerbation (acute phase of a disorder). It seems that neurotransmitters’ imbalance, induced by different weather variables—temperature, humidity, and luminosity—leads to the exacerbation of some disorders or to the triggering of violent and suicidal behavior [ 10 , 12 , 22 ]. As an example, an observed condition was suicide attempt, whose association with heat was reported to be of statistical significance. It seems that patients who previously attempted suicide have indeed a higher susceptibility to heat. In one study, differently from the first-attempt patients, who were vulnerable during the warm season only, the patients who had tried suicide multiple times were at higher risk during the entire year, in cases in which the temperature rose 5 °C [ 121 ].

Additionally, the cognition impairment caused by some mental disorders may also increase heat-susceptibility. There may be a lack of perception about the need to go to a cooler area or to take off extra layers of clothes to cool off the body [ 141 ].

At advanced ages, the delay and impairment to control heat maintenance is physiologically explained, since the receptor system and also the areas in the brain responsible for this function lose their efficiency over time, facilitating a higher body temperature [ 141 ].

Mentally ill patients as well as the elderly population have both a higher chance of being social isolated or living in nursing homes, which has also proved to increase risk of heat-related deaths or heat stress [ 11 ].

Similarly, poverty was found to further enhance the risk of heat-related death [ 86 ]. A possible reason for this susceptibility could be poor housing conditions. As previously discussed, low- and middle-income countries accounted for less than one-third of the studies. In addition, these regions rely on a less prepared healthcare system, which, nowadays, cannot accommodate the demand. In the future, in the absence of effective policies, these patients might become undertreated.

Finally, addressing not only the mechanisms surrounding the disorders, but also the socioeconomic vulnerabilities in the background may avoid the acute need for healthcare services.

5. Conclusions

This review is the first one to systematically assess and analyze the impact of CC on psychiatric health systems worldwide.

We found, based on strong evidence, that warmer temperatures, including heatwaves, can increase the demand uniformly for all types of medical care. Based on fewer number of studies, we also found that extreme events increase demand for all types of services. We support the hypothesis that, if public policies act to increase the recovery power of susceptible communities, fewer of these aftermath symptoms—anxiety, fear, and sadness—will become burdening disorders, and, therefore, lower numbers of EDV, HA, etc., will be required.

In this context, we found and listed three main gaps in the literature, which need to be properly addressed by scientific research in the future: (i) the low number of studies from low- and middle-income countries measuring health services utilization due to CC; (ii) the lack of studies carried out in the aftermath of extreme events using objective measures, as HA or EDV; and (iii) the poor approach of less common mental disorders. They are listed from F50–F99, in ICD-10th.

The lack of studies from low- and middle-income countries prevented us from measuring uniformly across the globe how health systems are affected, since the evidence is derived mostly from richer countries. Even though we found no difference of service utilization between low- and middle- when compared to high income-countries, we raise the concern that these assistance numbers from poorer countries are likely to be underrated. This could be explained by the fact that they do not have the same budget allocated to healthcare and that the population may face difficulties—financial, geographical, or transportation—in accessing health facilities.

Considering the continuous increase in numbers of psychiatric patients, individuals and health systems may witness more significant overwhelm than the one presented here, as temperatures rise and extreme events become more frequent. Therefore, additional public policies are the most effective way to help populations adapt, reducing the health impacts and, finally, avoiding the extra demand on public and private healthcare systems worldwide.

6. Strengths and Limitations

The use of mental health services, in terms of extra demand caused by CC, is an important strength. Still, we acknowledge that the use of services requires, firstly, the existence of functional and effective services, and these might not exist in some studied countries. Additionally, cognitive and educational access is needed for a patient’s clarity regarding when to seek healthcare. Therefore, this SLR may not reflect the magnitude of the impact of CC on MH disorders.

It has been pointed out that the lack of studies about extreme events and MH care use did not permit a vast analysis, as was the case for the ‘meteorological section’. There is a need to better elucidate this issue and the difference between the punctual distress after extreme events measured by community visits and, effectively, long-lasting and burdening disease.

Given the extensive number of studies and results we had access to, the forest plot ( Figure 5 ) is based on significant results and on relative risk-based studies only. Despite representing the biggest part of studies, we acknowledge that it may have prevented the reader from having another perspective.

Finally, the use of the ‘NIH Quality Assessment Tool’ is considered, by some authors, as not being the most appropriate tool. We acknowledge that, by having chosen this tool, we might have incurred potential bias. Nonetheless, all efforts were made to avoid this issue.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/ijerph20021190/s1 , Figure S1. Mental and other health impacts studied with climate change in PubMed (until 2022).; Table S1. Search terms used on PubMed for the elaboration of Figure S1; Table S2. Detailed search terms and its sources used for this review; Figure S2. International Classification of Diseases 10th revision (ICD-10) with detailed information from the subgroup of the psychiatric chapter. Source; Figure S3. With the detailed information from the 105 retrieved studies; Table S3. Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies.

Funding Statement

This research was supported by a scholarship of the German Catholic Academic Exchange Service (Katholischer Akademischer Ausländer-Dienst).

Author Contributions

J.F.C. developed the research idea with input from R.S., T.M. and P.D.; J.F.C. and A.Y.H. conducted the literature review. J.F.C. wrote the manuscript, with input from A.Y.H. and revisions from R.S., T.M. and P.D. All authors have read and agreed to the published version of the manuscript.

Institutional Review Board Statement

Informed consent statement, data availability statement, conflicts of interest.

The authors declare no conflict of interest.

Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

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Study says since 1979 climate change has made heat waves last longer, spike hotter, hurt more people

Tourists visit the ancient Acropolis hill during a heat wave in Athens, Greece, on July 21, 2023. (AP Photo/Petros Giannakouris)

FILE - Tourists visit the ancient Acropolis hill during a heat wave in Athens, Greece, on July 21, 2023. Climate change is making heat waves crawl slower across the globe and last longer with higher temperatures over larger areas, a new study finds. (AP Photo/Petros Giannakouris, File)

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FILE - A woman uses a shirt to shield from the sun as she walks at an outdoor shopping mall on a sweltering day in Beijing, July 6, 2023. Climate change is making heat waves crawl slower across the globe and last longer with higher temperatures over larger areas, a new study finds. (AP Photo/Andy Wong, File)

FILE - A security guard wearing an electric fan on his neck wipes his sweat on a hot day in Beijing, July 3, 2023. Climate change is making heat waves crawl slower across the globe and last longer with higher temperatures over larger areas, a new study finds. (AP Photo/Andy Wong, File)

FILE - A girl drinks water from a public fountain tap in Madrid, Spain, July 18, 2023. Climate change is making heat waves crawl slower across the globe and last longer with higher temperatures over larger areas, a new study finds. (AP Photo/Paul White, File)

FILE - A woman wearing sun protection headgear and sunglasses swims as residents cool off on a sweltering day at an urban waterway in Beijing, July 10, 2023. Climate change is making heat waves crawl slower across the globe and last longer with higher temperatures over larger areas, a new study finds. (AP Photo/Andy Wong, File)

Climate change is making giant heat waves crawl slower across the globe and they are baking more people for a longer time with higher temperatures over larger areas, a new study finds.

Since 1979, global heat waves are moving 20% more slowly — meaning more people stay hot longer — and they are happening 67% more often, according to a study in Friday’s Science Advances. The study found the highest temperatures in the heat waves are warmer than 40 years ago and the area under a heat dome is larger.

Studies have shown heat waves worsening before, but this one is more comprehensive and concentrates heavily on not just temperature and area, but how long the high heat lasts and how it travels across continents, said study co-authors and climate scientists Wei Zhang of Utah State University and Gabriel Lau of Princeton University.

From 1979 to 1983, global heat waves would last eight days on average, but by 2016 to 2020 that was up to 12 days, the study said.

Eurasia was especially hit harder with longer lasting heat waves, the study said. Heat waves slowed down most in Africa, while North America and Australia saw the biggest increases in overall magnitude, which measures temperature and area, according to the study.

A woman uses a shirt to shield from the sun as she walks at an outdoor shopping mall on a sweltering day in Beijing, July 6, 2023. (AP Photo/Andy Wong)

“This paper sends a clear warning that climate change makes heat waves yet more dangerous in more ways than one,” said Lawrence Berkeley National Lab climate scientist Michael Wehner, who wasn’t part of the research.

Just like in an oven, the longer the heat lasts, the more something cooks. In this case it’s people, the co-authors said.

“Those heat waves are traveling slower and so slower so that basically means that ... there’s a heat wave sitting there and those heat waves could stay longer in the region,” Zhang said. “And the adverse impacts on our human society would be huge and increasing over the years.”

The team conducted computer simulations showing this change was due to heat-trapping emissions that come from the burning of coal, oil and natural gas. The study found climate change’s fingerprint by simulating a world without greenhouse gas emissions and concluding it could not produce the worsening heat waves observed in the last 45 years.

The study also looks at the changes in weather patterns that propagate heat waves. Atmospheric waves that move weather systems along, such as the jet stream, are weakening, so they are not moving heat waves along as quickly — west to east in most but not all continents, Zhang said.

A girl drinks water from a public fountain tap in Madrid, Spain, July 18, 2023. (AP Photo/Paul White)

Several outside scientists praised the big picture way Zhang and colleagues examined heat waves, showing the interaction with weather patterns and their global movement and especially how they are slowing down.

This shows “how heat waves evolve in three dimensions and move regionally and across continents rather than looking at temperatures at individual locations,” said Kathy Jacobs, a University of Arizona climate scientist who wasn’t part of the study.

“One of the most direct consequences of global warming is increasing heat waves,” said Woodwell Climate Research Center scientist Jennifer Francis, who wasn’t part of the study. “These results put a large exclamation point on that fact.”

Read more of AP’s climate coverage at http://www.apnews.com/climate-and-environment

Follow Seth Borenstein on X at @borenbears

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The two sides of Guyana: a green champion and an oil producer

Camila Domonoske

Emily Kwong

Sea levels in Guyana are rising several times faster than the global average. High tides sometimes spill over the seawall that is meant to protect the coastline. Ryan Kellman/NPR hide caption

Sea levels in Guyana are rising several times faster than the global average. High tides sometimes spill over the seawall that is meant to protect the coastline.

For Guyana the potential wealth from oil development was irresistible — even as the country faces rising seas. Today on the show, host Emily Kwong talks to reporter Camila Domonoske about her trip to Guyana and how the country is grappling with its role as a victim of climate change while it moves forward with drilling more oil. (encore)

For more of Camila's reporting and pictures from her visit, check out " Guyana is a poor country that was a green champion. Then Exxon discovered oil ."

Want to more about how countries around the world are grappling with climate change? Write us at [email protected] to let us know — your suggestion might become a future episode!

Listen to Short Wave on Spotify , Apple Podcasts and Google Podcasts .

Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave .

This episode was produced for Morning Edition by Taylor Haney and edited by Rafael Nam. Photos by Ryan Kellman. Tamica Garnett contributed to this report. It was edited for Short Wave by Sara Sarasohn, produced by Thomas Lu, and fact-checked by Margaret Cirino. The audio engineer for this episode was Stu Rushfield.

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