Extreme weather seems to make the headlines almost every week, as disasters increasingly strike out of season, break records, and hit places they never have before.
Decades of scientific research has proven that human-caused climate change is making some disasters more dangerous and more frequent. The burning of fossil fuels like oil, gas, and coal releases carbon dioxide into the Earth’s atmosphere, where it traps heat, warms the planet, and alters the conditions in which extreme weather forms. These changes are happening more rapidly than at any time in the last 800,000 years, according to climate records.
Below, we break down what experts know — and what they don’t — about the connections between climate change and extreme heat.
The relationship between climate change and heat waves is perhaps the most straightforward of any disaster. “If we have an extreme heat wave, the null hypothesis is, ‘Climate change is making that worse,’” Andrew Dessler, a professor of atmospheric sciences at Texas A&M University, told Grist after a record-breaking heatwave hit the Pacific Northwest in 2021. The planet has already warmed 2 degrees Fahrenheit compared to pre-industrial times, and most heat waves we’ve experienced since have either been caused or strengthened by that. In 2020, scientists concluded that extreme heat in Siberia — with temperatures nearing 100 degrees in the Arctic Circle — was made 600 times more likely because of greenhouse gas emissions.
Cities in the U.S. are seeing 100-degree days more often, and they’re not just reserved for the dead of summer. Some places, like Houston, have hit triple digits in February. Cities with mild climates might be ill-equipped to respond to the new normal, and will need to invest in interventions like better warning systems and outreach, subsidizing air conditioning installations in low-income housing, maintaining a network of public cooling centers and transportation services during heat waves, and strengthening the electrical grid to withstand the additional energy load.
Policies barring utility companies from disconnecting electric services can also protect vulnerable residents, who may be afraid to run their AC all day due to the costs. Forty states have disconnection moratoriums during extreme cold — but only 21 have similar laws for extreme heat.
Nighttime temperatures are rising as well, intensifying the risk of heat waves. This is especially troubling for people who don’t have access to air conditioning (over 35 million people in the U.S., for example), or those who live in urban heat islands, where the abundance of heat-trapping concrete combined with a lack of trees and shade in some neighborhoods can cause temperatures to rise 15 to 20 degrees higher than neighborhoods with parks and green spaces.
Extreme heat can cause a myriad of health problems and even be deadly, particularly for the elderly, those who work outdoors, unhoused people, and people with pre-existing heart or lung conditions. Even for healthy adults, extreme heat can make it difficult for the body to cool itself off, which puts acute stress on the heart and kidneys. A recent study found that chronic heat exposure ages the body more than habitual smoking. Between 2004 and 2021, the number of Americans who officially died from heat exposure rose by 439 percent. On average over the last 30 years, heat waves have killed more people than hurricanes, floods, or tornadoes.
Even though it’s becoming more common and more dangerous, FEMA still does not classify extreme heat as a natural disaster, so federal funding to support local relief efforts is not available. Labor unions, environmental groups, and health professionals are pushing the federal agency to change that. Some advocates even say that heat waves should be named and ranked on a simple scale, like hurricanes are, to increase public awareness about the risks of extreme heat. For example, a pilot program in Seville, Spain, named heat waves (similar to hurricanes), and ranked them in three classifications based on severity. Each category triggered specific alerts and public health interventions like cooling centers and wellness checks.