persuasive article on climate change

Why climate change is still the greatest threat to human health

Polluted air and steadily rising temperatures are linked to health effects ranging from increased heart attacks and strokes to the spread of infectious diseases and psychological trauma.

People around the world are witnessing firsthand how climate change can wreak havoc on the planet. Steadily rising average temperatures fuel increasingly intense wildfires, hurricanes, and other disasters that are now impossible to ignore. And while the world has been plunged into a deadly pandemic, scientists are sounding the alarm once more that climate change is still the greatest threat to human health in recorded history .

As recently as August—when wildfires raged in the United States, Europe, and Siberia—World Health Organization Director-General Tedros Adhanom Ghebreyesus said in a statement that “the risks posed by climate change could dwarf those of any single disease.”

On September 5, more than 200 medical journals released an unprecedented joint editorial that urged world leaders to act. “The science is unequivocal,” they write. “A global increase of 1.5°C above the pre-industrial average and the continued loss of biodiversity risk catastrophic harm to health that will be impossible to reverse.”

Despite the acute dangers posed by COVID-19, the authors of the joint op-ed write that world governments “cannot wait for the pandemic to pass to rapidly reduce emissions.” Instead, they argue, everyone must treat climate change with the same urgency as they have COVID-19.

Here’s a look at the ways that climate change can affect your health—including some less obvious but still insidious effects—and why scientists say it’s not too late to avert catastrophe.

Air pollution

Climate change is caused by an increase of carbon dioxide and other greenhouse gases in Earth’s atmosphere, mostly from fossil fuel emissions. But burning fossil fuels can also have direct consequences for human health. That’s because the polluted air contains small particles that can induce stroke and heart attacks by penetrating the lungs and heart and even traveling into the bloodstream. Those particles might harm the organs directly or provoke an inflammatory response from the immune system as it tries to fight them off. Estimates suggest that air pollution causes anywhere between 3.6 million and nine million premature deaths a year.

“The numbers do vary,” says Andy Haines , professor of environmental change and public health at the London School of Hygiene and Tropical Medicine and author of the recently published book Planetary Health . “But they all agree that it’s a big public health burden.”

People over the age of 65 are most susceptible to the harmful effects of air pollution, but many others are at risk too, says Kari Nadeau , director of the Sean N. Parker Center for Allergy and Asthma Research at Stanford University. People who smoke or vape are at increased risk, as are children with asthma.

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Air pollution also has consequences for those with allergies. Carbon dioxide increases the acidity of the air, which then pulls more pollen out from plants. For some people, this might just mean that they face annoyingly long bouts of seasonal allergies. But for others, it could be life-threatening.

“For people who already have respiratory disease, boy is that a problem,” Nadeau says. When pollen gets into the respiratory pathway, the body creates mucus to get rid of it, which can then fill up and suffocate the lungs.

Even healthy people can have similar outcomes if pollen levels are especially intense. In 2016, in the Australian state of Victoria, a severe thunderstorm combined with high levels of pollen to induce what The Lancet has described as “the world’s largest and most catastrophic epidemic of thunderstorm asthma.” So many residents suffered asthma attacks that emergency rooms were overwhelmed—and at least 10 people died as a result.

Climate change is also causing wildfires to get worse, and wildfire smoke is especially toxic. As one recent study showed, fires can account for 25 percent of dangerous air pollution in the U.S. Nadeau explains that the smoke contains particles of everything that the fire has consumed along its path—from rubber tires to harmful chemicals. These particles are tiny and can penetrate even deeper into a person’s lungs and organs. ( Here’s how breathing wildfire smoke affects the body .)

Extreme heat

Heat waves are deadly, but researchers at first didn’t see direct links between climate change and the harmful impacts of heat waves and other extreme weather events. Haines says the evidence base has been growing. “We have now got a number of studies which has shown that we can with high confidence attribute health outcomes to climate change,” he says.

Most recently, Haines points to a study published earlier this year in Nature Climate Change that attributes more than a third of heat-related deaths to climate change. As National Geographic reported at the time , the study found that the human toll was even higher in some countries with less access to air conditioning or other factors that render people more vulnerable to heat. ( How climate change is making heat waves even deadlier .)

That’s because the human body was not designed to cope with temperatures above 98.6°F, Nadeau says. Heat can break down muscles. The body does have some ways to deal with the heat—such as sweating. “But when it’s hot outside all the time, you cannot cope with that, and your heart muscles and cells start to literally die and degrade,” she says.

If you’re exposed to extreme heat for too long and are unable to adequately release that heat, the stress can cause a cascade of problems throughout the body. The heart has to work harder to pump blood to the rest of the organs, while sweat leeches the body of necessary minerals such as sodium and potassium. The combination can result in heart attacks and strokes .

Dehydration from heat exposure can also cause serious damage to the kidneys, which rely on water to function properly. For people whose kidneys are already beginning to fail—particularly older adults—Nadeau says that extreme heat can be a death sentence. “This is happening more and more,” she says.

Studies have also drawn links between higher temperatures and preterm birth and other pregnancy complications. It’s unclear why, but Haines says that one hypothesis is that extreme heat reduces blood flow to the fetus.

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Food insecurity.

One of the less direct—but no less harmful—ways that climate change can affect health is by disrupting the world’s supply of food.

Climate change both reduces the amount of food that’s available and makes it less nutritious.   According to an Intergovernmental Panel on Climate Change (IPCC) special report , crop yields have already begun to decline as a result of rising temperatures, changing precipitation patterns, and extreme weather events. Meanwhile, studies have shown that increased carbon dioxide in the atmosphere can leech plants of zinc, iron, and protein—nutrients that humans need to survive.

Malnutrition is linked to a variety of illnesses, including heart disease, cancer, and diabetes. It can also increase the risk of stunting, or impaired growth , in children, which can harm cognitive function.

Climate change also imperils what we eat from the sea. Rising ocean temperatures have led many fish species to migrate toward Earth’s poles in search of cooler waters. Haines says that the resulting decline of fish stocks in subtropic regions “has big implications for nutrition,” because many of those coastal communities depend on fish for a substantial amount of the protein in their diets.

This effect is likely to be particularly harmful for Indigenous communities, says Tiff-Annie Kenny, a professor in the faculty of medicine at Laval University in Quebec who studies climate change and food security in the Canadian Arctic. It’s much more difficult for these communities to find alternative sources of protein, she says, either because it’s not there or because it’s too expensive. “So what are people going to eat instead?” she asks.

Infectious diseases  

As the planet gets hotter, the geographic region where ticks and mosquitoes like to live is getting wider. These animals are well-known vectors of diseases such as the Zika virus, dengue fever, and malaria. As they cross the tropics of Cancer and Capricorn, Nadeau says, mosquitoes and ticks bring more opportunities for these diseases to infect greater swaths of the world.

“It used to be that they stayed in those little sectors near the Equator, but now unfortunately because of the warming of northern Europe and Canada, you can find Zika in places you wouldn’t have expected,” Nadeau says.

In addition, climate conditions such as temperature and humidity can impact the life cycle of mosquitoes. Haines says there’s particularly good evidence showing that, in some regions, climate change has altered these conditions in ways that increase the risk of mosquitos transmitting dengue .

There are also several ways in which climate change is increasing the risk of diseases that can be transmitted through water, such as cholera, typhoid fever, and parasites. Sometimes that’s fairly direct, such as when people interact with dirty floodwaters. But Haines says that drought can have indirect impacts when people, say, can’t wash their hands or are forced to drink from dodgier sources of freshwater.

Mental health

A common result of any climate-linked disaster is the toll on mental health. The distress caused by drastic environmental change is so significant that it has been given its own name— solastalgia .

Nadeau says that the effects on mental health have been apparent in her studies of emergency room visits arising from wildfires in the western U.S. People lose their homes, their jobs, and sometimes their loved ones, and that takes an immediate toll. “What’s the fastest acute issue that develops? It’s psychological,” she says. Extreme weather events such as wildfires and hurricanes cause so much stress and anxiety that they can lead to post-traumatic stress disorder and even suicide in the long run.

Another common factor is that climate change causes disproportionate harm to the world’s most vulnerable people. On September 2, the Environmental Protection Agency (EPA) released an analysis showing that racial and ethnic minority communities are particularly at risk . According to the report, if temperatures rise by 2°C (3.6°F), Black people are 40 percent more likely to live in areas with the highest projected increases in related deaths. Another 34 percent are more likely to live in areas with a rise in childhood asthma.

Further, the effects of climate change don’t occur in isolation. At any given time, a community might face air pollution, food insecurity, disease, and extreme heat all at once. Kenny says that’s particularly devastating in communities where the prevalence of food insecurity and poverty are already high. This situation hasn’t been adequately studied, she says, because “it’s difficult to capture these shocks that climate can bring.”

Why there’s reason for hope

In recent years, scientists and environmental activists have begun to push for more research into the myriad health effects of climate change. “One of the striking things is there’s been a real dearth of funding for climate change and health,” Haines says. “For that reason, some of the evidence we have is still fragmentary.”

Still, hope is not lost. In the Paris Agreement, countries around the world have pledged to limit global warming to below 2°C (3.6°F)—and preferably to 1.5°C (2.7°F)—by cutting their emissions. “When you reduce those emissions, you benefit health as well as the planet,” Haines says.

Meanwhile, scientists and environmental activists have put forward solutions that can help people adapt to the health effects of climate change. These include early heat warnings and dedicated cooling centers, more resilient supply chains, and freeing healthcare facilities from dependence on the electric grid.

Nadeau argues that the COVID-19 pandemic also presents an opportunity for world leaders to think bigger and more strategically. For example, the pandemic has laid bare problems with efficiency and equity that have many countries restructuring their healthcare facilities. In the process, she says, they can look for new ways to reduce waste and emissions, such as getting more hospitals using renewable energy.

“This is in our hands to do,” Nadeau says. “If we don’t do anything, that would be cataclysmic.”

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Climate change affects your life in 3 big ways, a new report warns

Alejandra Borunda

Lauren Sommer

Rebecca Hersher

Climate change causes tens of billions of dollars in economic damage in the United States every year, according to a new assessment. Many survivors of climate-driven disasters, including hurricanes, floods and wildfires, struggle for months or even years to repair their homes or find new stable housing. Here, a Louisiana home damaged by a hurricane sits waiting for unaffordable repairs. Ryan Kellman/NPR hide caption

Climate change is expensive, deadly and preventable, according to the new National Climate Assessment, the most sweeping, sophisticated federal analysis of climate change compiled to date.

Released every five years, the National Climate Assessment is a congressionally mandated evaluation of the effects of climate change on American life. This new fifth edition paints a picture of a nation simultaneously beset by climate-driven disasters and capable of dramatically reducing emissions of planet-warming gasses in the near future.

This is the first time the assessment includes standalone chapters about climate change's toll on the American economy, as well as the complex social factors driving climate change and the nation's responses. And, unlike past installments, the new assessment draws heavily from social science, including history, sociology, philosophy and Indigenous studies.

The new approach adds context and relevance to the assessment's robust scientific findings, and underscores the disproportionate danger that climate change poses to poor people, marginalized communities, older Americans and those who work outdoors.

"Climate change affects us all, but it doesn't affect us all equally," says climate scientist Katharine Hayhoe, one of the authors of the assessment. But threaded throughout the report are case studies and research summaries highlighting ways "climate action can create a more resilient and just country," she says.

This is also the first time the National Climate Assessment will be translated into Spanish, although the Spanish-language version won't be available until the spring, according to the White House.

The National Climate Assessment is extremely influential in legal and policy circles, and affects everything from court cases about who should foot the bill for wildfire damage, to local decisions about how tall to build coastal flood barriers. "It really shapes the way that people understand, and therefore act, in relation to climate change," says Michael Burger, the director of the Sabin Center for Climate Change Law at Columbia University.

Hundreds of scientists from universities, industry, and federal agencies contributed to the report. They reviewed cutting-edge research published since the last report and contextualized it in decades of foundational climate research.

The fifth edition of the assessment arrives as millions of Americans are struggling with the effects of a hotter Earth. Dramatic and deadly wildfires, floods and heat waves killed hundreds of people in the United States in 2023.

And, while federal spending on renewable energy and disaster preparedness has increased, the U.S. is also investing in new fossil fuel infrastructure that is not compatible with avoiding catastrophic warming later this century.

Here are the three big takeaways from the Fifth National Climate Assessment . More information about the specific effects of climate change in your area can be found in the assessment's regional chapters .

Windmills near Whitewater, Calif., in 2020. Reducing fossil fuel use and investing more in renewable energy sources such as wind will help the U.S. avoid billions of dollars of economic costs and help Americans live longer, healthier lives according to the Fifth National Climate Assessment. Ringo H.W. Chiu/AP hide caption

Windmills near Whitewater, Calif., in 2020. Reducing fossil fuel use and investing more in renewable energy sources such as wind will help the U.S. avoid billions of dollars of economic costs and help Americans live longer, healthier lives according to the Fifth National Climate Assessment.

Climate change makes life more expensive

Food, housing, labor – it all gets pricier as the Earth heats up, according to the National Climate Assessment.

Climate-driven weather disasters, like heat waves, floods, hurricanes and wildfires, are particularly expensive. They destroy homes and businesses, wreck crops and create supply shortages by delaying trucks, ships and trains. Such disasters make it more likely that families will go bankrupt, and that municipal governments will run deficits, the authors note.

Weather-related disasters in the U.S. cause about $150 billion each year in direct losses, according to the report. That's a lot of money – roughly equal to the annual budget for the Energy Department – and it's only expected to go up as the Earth gets hotter.

And that's all before factoring in the less obvious or tangible costs of climate change. For example, healthcare bills for people who are sicker because of extreme heat, or have respiratory illness brought on by breathing in mold after a flood. Exposure to wildfire smoke alone costs billions of dollars a year in lost earnings, the assessment notes – a burden that falls disproportionately on poor people who work outdoors.

"The research indicates that people who are lower income have more trouble adapting [to climate change], because adaptation comes at a cost," says Solomon Hsiang, a climate economist at the University of California, Berkeley and a lead author of the assessment.

For example, one of the simplest ways to adapt to severe heat waves is to run your air conditioner more. But "if people can't pay for it, then [they] can't protect themselves," explains Hsiang.

And the hotter it gets, the more profound the economic harm, assessment warns. Twice as much planetary warming leads to more than twice as much economic harm, the assessment warns.

A roadside memorial to those who died in the wildfire that swept through the town of Lahaina, Hawaii in August. The latest National Climate Assessment underscores the many ways that climate change is already making Americans sick, and even killing them. Claire Harbage/NPR hide caption

A roadside memorial to those who died in the wildfire that swept through the town of Lahaina, Hawaii in August. The latest National Climate Assessment underscores the many ways that climate change is already making Americans sick, and even killing them.

Climate change makes people sick and often kills them

Since the previous NCA was released five years ago, the health costs of climate change have gone from theoretical to personal for many Americans.

The most obvious risk? Extreme weather, particularly heat, says Mary Hayden, the lead author of the chapter examining human health. Heat waves have become hotter, longer, and more dangerous, and they're hitting areas that aren't ready for them–like the "record-shattering" heat dome that descended on the Pacific Northwest in 2021 and caused hundreds of deaths.

But it's not just heat. Wildfire smoke can send people thousands of miles from the fires to hospitals with respiratory problems and heart disease complications. Hurricanes can disrupt people's access to healthcare: when a clinic is flooded or people are displaced, for example, kidney patients can't get dialysis treatment .

In most cases, the people who bear the brunt of the disasters are those already at risk: poor communities, communities of color, women, people with disabilities, and other marginalized groups. Temperatures in formerly redlined neighborhoods in cities across the country can soar nearly 15 degrees Fahrenheit hotter than wealthier areas just blocks away, putting residents at much higher risk of heat exposure.

The assessment also homes in on research tracking less-obvious health impacts. Living through climate disasters, for example, can leave lasting emotional scars. "We're not just talking about [people's] physical health–we're talking about their mental health. We're talking about their spiritual health. We're talking about the health and well-being of communities which are being affected by this," Hayden says.

That means recognizing the long-term effects on communities like Paradise, California, where people still deal with deep emotional trauma five years after their town burned in the 2018 Camp Fire. The report also flags the growing emotional toll on children and young people, for whom anxiety about the future of the planet is bleeding into all parts of their lives.

A lobsterman paddles out to his boat in a harbor in Maine. Climate change is disrupting ways of living with, and from, the ocean. Ryan Kellman hide caption

Climate change threatens people's special, sacred places and practices

The places, cultural practices, and traditions that anchor many communities are also in flux because of climate change.

Fishing communities are seeing their livelihoods shift or collapse. The Northeast's iconic lobster fishery, the single most economically valuable in the country, has withered as marine heatwaves sweep through the regional seas . Shrinking snowpack and too-warm temperatures are interrupting opportunities for beloved recreational activities, like skiing or ice fishing .

Indigenous communities are being forced to adjust to new climate realities, which are disrupting traditional food-gathering traditions. In Palau, a monthly tradition of catching fish at a particularly low tide has been upset by sea level rise, which keeps water levels too high to trap fish in the historically-used places . Sea level rise is also forcing coastal communities to re-think their very existence, pulling apart the social fabric that has developed over generations.

But many communities – Indigenous people, farmers and fishers, groups that have lived tightly connected to their environments for a long time – have deep stores of resilience from which to draw, says Elizabeth Marino, a sociologist and the lead author of the chapter on social transformations. "There is quite a lot of wisdom in place to adapt to and even mitigate climate change," she says. "It allows people to come up with solutions that fit the lives that they lead, and that's also a place of hope."

The fixes to climate change can make Americans' lives better

The fifth assessment lays out a stark picture of the climate challenges the U.S. faces. Keeping planetary warming to "well below" 2 degrees Celsius (3.6 degrees Fahrenheit), the goal of the international Paris Agreement, will require immediate, enormous cuts to fossil fuel emissions in the U.S and beyond. Keeping warming below 1.5 degrees Celsius (2.7 degrees Fahrenheit), an ambitious target written into the Agreement, will be even harder, the report says.

But it also points out many successful efforts underway to adapt to the new reality and to prevent worse outcomes.

"It's not the message that if we don't hit 1.5 degrees, we're all going to die," says Hayhoe. "It's the message that everything we do matters. Every 10th of a degree of warming we avoid, there's a benefit to that."

Addressing fossil fuel-driven climate change can also help people live healthier lives, stresses J. Jason West, the lead author on a chapter on air quality. Dialing back fossil fuel emissions would help prevent further climate change and also lessen the kinds of air pollution most harmful to human health." There really is a lot of opportunity to take action that would resolve both of those problems at the same time," West says.

There's been a subtle shift in the report's perspective since the last one, says Candis Callison, a sociologist and author of the report. There's now a clear acknowledgement, developed through years of rigorous research, that the fossil fuel-powered society the U.S. built over generations was profoundly unjust. Many pollution-producing coal or gas power plants were sited in communities of color rather than white communities, affecting people's health outcomes for generations. And decisions about land and water use for energy extraction often excluded tribal communities , with consequences still playing out today.

The transition forward can look different, she says. "Climate change actually provides us with an opportunity to address some of those inequities and injustices–and to respond to these impacts," Callison says. "That's really a powerful thing."

• National Climate Assessment
• 5th National Climate Assessment
• Fifth National Climate Assessment
• greenhouse gas emissions
• sea level rise
• carbon dioxide
• global warming
• climate change

Why climate change is still the greatest threat to human health

Polluted air and steadily rising temperatures are linked to health effects ranging from increased heart attacks and strokes to the spread of infectious diseases and psychological trauma..

People around the world are witnessing firsthand how climate change can wreak havoc on the planet. Steadily rising average temperatures fuel increasingly intense wildfires, hurricanes, and other disasters that are now impossible to ignore. And while the world has been plunged into a deadly pandemic, scientists are sounding the alarm once more that climate change is still the greatest threat to human health in recorded history .

As recently as August—when wildfires raged in the United States, Europe, and Siberia—World Health Organisation Director-General Tedros Adhanom Ghebreyesus said in a statement that “the risks posed by climate change could dwarf those of any single disease.”

On September 5, more than 200 medical journals released an unprecedented joint editorial that urged world leaders to act. “The science is unequivocal,” they write. “A global increase of 1.5°C above the pre-industrial average and the continued loss of biodiversity risk catastrophic harm to health that will be impossible to reverse.”

Despite the acute dangers posed by COVID-19, the authors of the joint op-ed write that world governments “cannot wait for the pandemic to pass to rapidly reduce emissions.” Instead, they argue, everyone must treat climate change with the same urgency as they have COVID-19.

Here’s a look at the ways that climate change can affect your health—including some less obvious but still insidious effects—and why scientists say it’s not too late to avert catastrophe.

Air pollution

Climate change is caused by an increase of carbon dioxide and other greenhouse gases in Earth’s atmosphere, mostly from fossil fuel emissions. But burning fossil fuels can also have direct consequences for human health. That’s because the polluted air contains small particles that can induce stroke and heart attacks by penetrating the lungs and heart and even travelling into the bloodstream. Those particles might harm the organs directly or provoke an inflammatory response from the immune system as it tries to fight them off. Estimates suggest that air pollution causes anywhere between 3.6 million and nine million premature deaths a year.

“The numbers do vary,” says Andy Haines , professor of environmental change and public health at the London School of Hygiene and Tropical Medicine and author of the recently published book Planetary Health . “But they all agree that it’s a big public health burden.”

People over the age of 65 are most susceptible to the harmful effects of air pollution, but many others are at risk too, says Kari Nadeau , director of the Sean N. Parker Centre for Allergy and Asthma Research at Stanford University. People who smoke or vape are at increased risk, as are children with asthma.

Air pollution also has consequences for those with allergies. Carbon dioxide increases the acidity of the air, which then pulls more pollen out from plants. For some people, this might just mean that they face annoyingly long bouts of seasonal allergies. But for others, it could be life-threatening.

“For people who already have respiratory disease, boy is that a problem,” Nadeau says. When pollen gets into the respiratory pathway, the body creates mucus to get rid of it, which can then fill up and suffocate the lungs.

Even healthy people can have similar outcomes if pollen levels are especially intense. In 2016, in the Australian state of Victoria, a severe thunderstorm combined with high levels of pollen to induce what The Lancet has described as “the world’s largest and most catastrophic epidemic of thunderstorm asthma.” So many residents suffered asthma attacks that emergency rooms were overwhelmed—and at least 10 people died as a result.

Climate change is also causing wildfires to get worse, and wildfire smoke is especially toxic. As one recent study showed, fires can account for 25 percent of dangerous air pollution in the U.S. Nadeau explains that the smoke contains particles of everything that the fire has consumed along its path—from rubber tires to harmful chemicals. These particles are tiny and can penetrate even deeper into a person’s lungs and organs. ( B ritish wildfires are getting more frequent. Here's what that means .)

Extreme heat

Heat waves are deadly, but researchers at first didn’t see direct links between climate change and the harmful impacts of heat waves and other extreme weather events. Haines says the evidence base has been growing. “We have now got a number of studies which has shown that we can with high confidence attribute health outcomes to climate change,” he says.

Most recently, Haines points to a study published earlier this year in Nature Climate Change that attributes more than a third of heat-related deaths to climate change. As National Geographic reported at the time , the study found that the human toll was even higher in some countries with less access to air conditioning or other factors that render people more vulnerable to heat. 

That’s because the human body was not designed to cope with temperatures above 37°C, Nadeau says. Heat can break down muscles. The body does have some ways to deal with the heat—such as sweating. “But when it’s hot outside all the time, you cannot cope with that, and your heart muscles and cells start to literally die and degrade,” she says.

If you’re exposed to extreme heat for too long and are unable to adequately release that heat, the stress can cause a cascade of problems throughout the body. The heart has to work harder to pump blood to the rest of the organs, while sweat leeches the body of necessary minerals such as sodium and potassium. The combination can result in heart attacks and strokes .

Dehydration from heat exposure can also cause serious damage to the kidneys, which rely on water to function properly. For people whose kidneys are already beginning to fail—particularly older adults—Nadeau says that extreme heat can be a death sentence. “This is happening more and more,” she says.

Studies have also drawn links between higher temperatures and preterm birth and other pregnancy complications. It’s unclear why, but Haines says that one hypothesis is that extreme heat reduces blood flow to the foetus.

Food insecurity

One of the less direct—but no less harmful—ways that climate change can affect health is by disrupting the world’s supply of food.

Climate change both reduces the amount of food that’s available and makes it less nutritious.   According to an Intergovernmental Panel on Climate Change (IPCC) special report , crop yields have already begun to decline as a result of rising temperatures, changing precipitation patterns, and extreme weather events. Meanwhile, studies have shown that increased carbon dioxide in the atmosphere can leech plants of zinc, iron, and protein—nutrients that humans need to survive.

Malnutrition is linked to a variety of illnesses, including heart disease, cancer, and diabetes. It can also increase the risk of stunting, or impaired growth , in children, which can harm cognitive function.

Climate change also imperils what we eat from the sea. Rising ocean temperatures have led many fish species to migrate toward Earth’s poles in search of cooler waters. Haines says that the resulting decline of fish stocks in subtropic regions “has big implications for nutrition,” because many of those coastal communities depend on fish for a substantial amount of the protein in their diets.

This effect is likely to be particularly harmful for Indigenous communities, says Tiff-Annie Kenny, a professor in the faculty of medicine at Laval University in Quebec who studies climate change and food security in the Canadian Arctic. It’s much more difficult for these communities to find alternative sources of protein, she says, either because it’s not there or because it’s too expensive. “So what are people going to eat instead?” she asks.

Infectious diseases 

As the planet gets hotter, the geographic region where ticks and mosquitoes like to live is getting wider. These animals are well-known vectors of diseases such as the Zika virus, dengue fever, and malaria. As they cross the tropics of Cancer and Capricorn, Nadeau says, mosquitoes and ticks bring more opportunities for these diseases to infect greater swaths of the world.

“It used to be that they stayed in those little sectors near the Equator, but now unfortunately because of the warming of northern Europe and Canada, you can find Zika in places you wouldn’t have expected,” Nadeau says.

In addition, climate conditions such as temperature and humidity can impact the life cycle of mosquitoes. Haines says there’s particularly good evidence showing that, in some regions, climate change has altered these conditions in ways that increase the risk of mosquitos transmitting dengue .

There are also several ways in which climate change is increasing the risk of diseases that can be transmitted through water, such as cholera, typhoid fever, and parasites. Sometimes that’s fairly direct, such as when people interact with dirty floodwaters. But Haines says that drought can have indirect impacts when people, say, can’t wash their hands or are forced to drink from dodgier sources of freshwater.

Mental health

A common result of any climate-linked disaster is the toll on mental health. The distress caused by drastic environmental change is so significant that it has been given its own name— solastalgia .

Nadeau says that the effects on mental health have been apparent in her studies of emergency room visits arising from wildfires in the western United States. People lose their homes, their jobs, and sometimes their loved ones, and that takes an immediate toll. “What’s the fastest acute issue that develops? It’s psychological,” she says. Extreme weather events such as wildfires and hurricanes cause so much stress and anxiety that they can lead to post-traumatic stress disorder and even suicide in the long run.

Another common factor is that climate change causes disproportionate harm to the world’s most vulnerable people. On September 2, the Environmental Protection Agency (EPA) released an analysis showing that racial and ethnic minority communities are particularly at risk . According to the report, if temperatures rise by 2°C (3.6°F), Black people are 40 percent more likely to live in areas with the highest projected increases in related deaths. Another 34 percent are more likely to live in areas with a rise in childhood asthma.

Further, the effects of climate change don’t occur in isolation. At any given time, a community might face air pollution, food insecurity, disease, and extreme heat all at once. Kenny says that’s particularly devastating in communities where the prevalence of food insecurity and poverty are already high. This situation hasn’t been adequately studied, she says, because “it’s difficult to capture these shocks that climate can bring.”

Why there’s reason for hope

In recent years, scientists and environmental activists have begun to push for more research into the myriad health effects of climate change. “One of the striking things is there’s been a real dearth of funding for climate change and health,” Haines says. “For that reason, some of the evidence we have is still fragmentary.”

Still, hope is not lost. In the Paris Agreement, countries around the world have pledged to limit global warming to below 2°C (3.6°F)—and preferably to 1.5°C (2.7°F)—by cutting their emissions. “When you reduce those emissions, you benefit health as well as the planet,” Haines says.

Meanwhile, scientists and environmental activists have put forward solutions that can help people adapt to the health effects of climate change. These include early heat warnings and dedicated cooling centres, more resilient supply chains, and freeing healthcare facilities from dependence on the electric grid.

Nadeau argues that the COVID-19 pandemic also presents an opportunity for world leaders to think bigger and more strategically. For example, the pandemic has laid bare problems with efficiency and equity that have many countries restructuring their healthcare facilities. In the process, she says, they can look for new ways to reduce waste and emissions, such as getting more hospitals using renewable energy.

“This is in our hands to do,” Nadeau says. “If we don’t do anything, that would be cataclysmic.”

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