Climate and Your Health

Medically Reviewed by Neha Pathak, MD on June 24, 2021

The year 2020 was one of the hottest on record, and this year is shaping up to be another scorcher. April 2021 marked the 436th month in a row with warmer-than-average temperatures.

The Earth is in the midst of a warming trend. Scientists expect we'll break more records in the years to come. As the planet warms, the glaciers recede, storms get stronger, droughts worsen, and the risks to our health increase.

Human activities, especially burning fossil fuels, have increased the release of carbon dioxide and other greenhouse gases. Those gases trap heat in the lower atmosphere and fuel the rising worldwide temperatures known as global warming. Climate change is the term scientists use to describe changes in heat and other weather patterns that happen over a long period of time.

"It's completely without any doubt that the planet is getting warmer and our summers are seeing more heat waves because of the burning of fossil fuels," says Aaron Bernstein, MD, interim director of the Center for Climate, Health, and the Global Environment at the Harvard T.H. Chan School of Public Health.

Extreme heat, poor air quality, and disease-carrying insects are just a few of the climate-based health threats we face. But it isn’t too late to slow these effects. Each one of us can do something to protect our planet, and our health.

When it comes to the impacts of climate change on our health, heat is "at the top of the list," says Lewis Ziska, PhD, an associate professor of environmental health sciences at Columbia University’s Mailman School of Public Health.

With rising global temperatures, heat waves happen more often, last longer, and are more intense.

More than one-third of heat-related deaths around the world can be linked to climate change from human activities, a recent study finds. In the United States, heat causes over 5,600 deaths each year.

The direct effects of heat waves include heat-related illnesses like heat exhaustion or heat stroke, but there are indirect effects, too. "Heat stresses the body," Bernstein says. "It makes maintaining your fluid balance difficult."

Older adults and people with chronic illnesses like diabetes or asthma are especially vulnerable to heat-related illnesses. So are those who can't afford air conditioning.

Some medications change the way our bodies respond to heat. "There's a whole range of drugs that affect the ability of your body to sweat," says Kristie Ebi, PhD, a professor in the Center for Health and the Global Environment at the University of Washington. Examples are blood pressure medicines and SSRI antidepressants. Diuretics meant to lower blood pressure dehydrate you more quickly in the heat.

As temperatures rise, air quality becomes less healthy. Burning fossil fuels not only contributes to climate change, it also puts more pollutants into the air.

On hot days, levels of a harmful gas called ozone rise in the atmosphere. Ozone damages your lungs and worsens lung diseases like asthma, COPD, and chronic bronchitis. This means more people with these conditions wind up in the hospital.

Rising temperatures also put more pollen into the air, creating extra troubles for people with allergies. Spring comes sooner and fall starts later, leading to a longer allergy season, Ebi says. "With higher carbon dioxide in the atmosphere, plants are growing faster and some of them are producing more pollen."

Mosquitoes like warm weather. They're also big fans of carbon dioxide. As northern cities heat up, these blood-sucking bugs migrate north, carrying with them diseases like West Nile, Zika, and chikungunya.

"As temperatures go up, mosquitoes are changing their geographic range," Ebi says. "Unless you've got a mountain or one of the Great Lakes, there's not much that's going to constrain mosquitoes from moving from one place to another."

Mosquitoes aren't the only pest we need to worry about. More intense storms bring flooding, creating ideal breeding conditions for the germs that carry infectious diseases like cryptosporidiosis, giardia, leptospirosis, and cholera.

"We have many studies showing that heavy rainfall events are causing outbreaks of waterborne diseases," Bernstein says. "We see the evidence that greenhouse gases are driving heavier downpours."

In 1993, Milwaukee, WI, had the largest documented outbreak of cryptosporidiosis in U.S. history. After a heavy storm, Cryptosporidium parvum, the parasite that causes this infection, which can lead to diarrhea, among other symptoms, contaminated the city's water supply. It sickened more than 400,000 people -- half the population at the time.

Climate change can also ruin your mood. Research shows that for every 1 degree rise in monthly average temperatures, suicides increase. Homicides also spike during heat waves.

Ziska offers one possible reason. "If you had warmer nighttime temperatures and you didn't have an air conditioner, and it becomes harder and harder for you to get a good night's sleep, you can imagine what that does to your mental health," he says.

Seeing your house go up in flames from a wildfire or returning to the rubble of your business after a hurricane can also strain your emotional state.

Even some of us who haven't felt the direct effects of climate change carry a general sense of unease about our planet's future that experts have termed "eco-anxiety." It’s the idea of worry that stems from the risk of climate change, Bernstein says. "It's this constant looming threat."

"The question of how bad it's going to be in the United States is a fraction of however bad it's going to be in lots of parts of the world," Bernstein says. "The countries that are least responsible for this are going to get the worst heat, the worst hurricanes, the worst effects on their food supply."

Countries that lack a well-developed infrastructure and health care system could bear even more of the burden from climate change. Food supply is one big area of concern. Rising carbon dioxide levels change the nutrient concentrations of crops like rice and wheat, making them heavier in starch and sugar, and lower in crucial nutrients like protein, zinc, and iron.

Climate scientists warn that we're on the brink of a climate change-fueled disaster, but we do have the power to curb global warming. "This is something we can do something about," Bernstein says. "And to be clear, we have been doing something about it."

He points to the Clean Air Act, which has reduced air pollution from cars and factories, and in the process saved hundreds of thousands of lives. Governments can take sweeping actions, like increasing the amount of green space in cities. But we don't have to wait for our elected officials to respond.

"Every single one of us can contribute to the solutions. And every action we take is important," Ebi says.

These simple steps are a great way to start -- and they can add up if enough people take them:

  • Buy energy-efficient appliances and vehicles.
  • Recycle paper and plastic.
  • Walk or bike to work if you can.
  • Turn up the thermostat a degree.
  • Switch off the lights when you leave a room.

Finally, make sure the people you elect to represent you are as concerned about climate change as you are, and are taking steps to address it. "At the end of the day, voting is by far one of the most important things we can do," Bernstein says.

Show Sources


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GlobalChange.Gov: "The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment."

World Health Organization: "Climate change and health."

U.S. Geological Survey: "What is the difference between global warming and climate change?"

Aaron Bernstein, MD, interim director, Center for Climate, Health, and the Global Environment, Harvard T.H. Chan School of Public Health, Boston.

Lewis Ziska, PhD, associate professor of environmental health sciences, Mailman School of Public Health, Columbia University, New York City.

Center for Climate and Energy Solutions: "Heat Waves and Climate Change."

Nature: "The burden of heat-related mortality attributable to recent human-induced climate change."

Cleveland Clinic: "Heat Illness."

U.S. Environmental Protection Agency: "Benefits and Costs of the Clean Air Act 1990-2020, the Second Prospective Study," "Climate Change Indicators: Heat-Related Illnesses," "Health Effects of Ozone Pollution."

Kristie Ebi, PhD, professor, Center for Health and the Global Environment, University of Washington, Seattle.

CDC: "Climate Change Decreases the Quality of the Air We Breathe," “Costs of Illness in the 1993 Waterborne Cryptosporidium Outbreak, Milwaukee, Wisconsin,” “Cryptosporidiosis.”

Harvard T.H. Chan School of Public Health: "Climate Change and Allergies."

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Nature Climate Change: "Higher temperatures increase suicide rates in the United States and Mexico."

The New York Times: "A Rise in Murder? Let's Talk About the Weather."

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