One hot-ass summer day in New York City.
Photo: Getty

The world is heating up and no one is safe, even in the richest country on Earth. Rising temperatures could kill thousands of us in the U.S., a new study finds.

The study, published Wednesday in the journal Science Advances, highlights how thousands of Americans could die under heat waves every 30 years if the world fails to meet the targets set forth in the Paris Agreement, which President Donald Trump announced he would withdraw the U.S. from in 2017. The number of deaths varies from city to city, and it’ll also vary depending on how much the world warms by 2100. That’s something we actually have the power to change.

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“We are no longer counting the impact of climate in change in terms of degrees of global warming, but rather in terms of number of lives lost,” co-lead author, Dann Mitchell, a researcher with the University of Bristol’s Cabot Institute, said in a statement.

The study looks specifically at 15 major cities in the U.S. and compared the number of heat-related deaths that could occur under three warming scenarios. The authors focus on the number of deaths during heat waves that are likely to occur once every 30 years as those types of heat events are “more relevant to climate change mitigation and adaptation action than rarer events” according to the study.

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Heat can lead to heat exhaustion and heat stroke, but it can also contribute to heart attacks and exacerbate asthma. Heat leads the number of weather-related deaths in the U.S., according to the Environmental Protection Agency. And it’s not just the United States: In 2010, a one-in-30-year heat wave broke temperature records and killed nearly 11,000 in Russia alone.

The 15 major cities—including New York, Seattle, San Francisco, Miami, Philly, and St. Louis—the authors from the University of Bristol looked at would witness different death counts based on the humidity and heat levels they’re projected to experience as the world continues to warm. In New York, where I live, some 1,980 more heat-related deaths may occur in a 2 degrees Celsius scenario versus the 3 degrees Celsius scenario.

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All told, if the world keeps warming within 2 degrees Celsius (3.6 degrees Fahrenheit) of preindustrial levels—the goal enshrined in the Paris Agreement—by the end of this century, the U.S. will see anywhere from 75 to 1,980 fewer heat-related deaths per city during a once every 30 year heat wave than if warming increased by 3 degrees Celsius (5.4 degrees Fahrenheit). Keeping the temperature to 1.5 degrees Celsius (2.7 degrees Fahrenheit), on the other hand, could save up to 2,716 lives per city in the U.S.

Just about every single city studied would see a reduction in the number of heat-related deaths if the world doesn’t reach a 3 degree Celsius increase. Atlanta is the only city that didn’t show this as it didn’t show a strong relationship between mortality and the hottest temperatures. But all cities would see fewer hot days if global warming is capped.

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The authors came to their conclusions after reviewing temperature trends from 1979 to 2013 across the U.S. They also looked at daily death counts and daily mean temperatures between 1987 and 2000 to project what the number of deaths may look like in the three warming scenarios.

The analysis isn’t without its caveats, though. The authors didn’t account for population changes in these cities, and we know cities are forever changing. People come and go. Different demographics also affect how many people can die from heat; older people are more likely to suffer from heat-related ailments. The study authors note that it doesn’t account for the aging U.S. population and that it would likely lead to increased mortality in these cities during heat waves.

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What’s clear from this analysis, however, is that climate change is going to kill people, and in fact it’s something that’s already happening. What this study shows, though, is that we can prevent more deaths if we take action to curb carbon emissions and limit global warming. That feels less likely under the current administration, but maybe presidential hopefuls will heed this warning. Lives are at stake.