WASHINGTON, June 6, 2019—The planet will warm by about 3 degrees Celsius above pre-industrial levels by the end of the century if the U.S. and other nations meet only their current commitments under the Paris climate agreement to reduce emissions of heat-trapping gases. According to a paper by U.S. and U.K. scientists published in Science Advances today, accelerating ambition to reduce global warming emissions to meet the Paris Agreement’s goal of limiting temperature rise to well below 2 degrees Celsius could prevent thousands of extreme heat-related deaths in cities across the U.S.

This first-of-its-kind study—led by Eunice Lo of the University of Bristol in the UK and co-authored by a team of researchers, including Peter Frumhoff, director of science and policy and chief climate scientist at the Union of Concerned Scientists (UCS), and Kristie L. Ebi, professor and researcher at the University of Washington’s School of Public Health—examines the impact on mortality rates of projected high temperatures associated with extreme heat expected to occur once every 30 years on average* in 15 U.S. cities: Atlanta, Boston, Chicago, Dallas, Detroit, Houston, Los Angeles, Miami, New York, Philadelphia, Phoenix, San Francisco, Seattle, St. Louis and Washington D.C.

“Climate change is not only affecting far away places but also the United States,” said Lo. “As temperatures rise, exposure of major U.S. cities to extreme heat will increase and more heat-related deaths will occur. The United States has emitted the largest amount of carbon dioxide in the world since the 18th century. Immediate and drastic emissions cuts are key to preventing large increases in heat-related deaths in the country.”

Climate change is already increasing the severity of extreme heat. If global temperatures reach 3 degrees Celsius, these cities would experience more severe heat waves than if temperature-rise is limited to 1.5 or 2 degrees Celsius. At 3 degrees Celsius, there would be between about 330 and 5,800 heat-related deaths per city for each 1-in-30-year event, with cities like Chicago, Los Angeles, Miami, New York and Philadelphia facing the highest number of fatalities. Limiting global temperature rise to 2 degrees Celsius avoids between about 70 and 1,980 extreme heat-related deaths per city. Even more heat related deaths—between about 110 and 2,720—can be avoided by achieving the 1.5 degrees Celsius threshold.

To view a spreadsheet highlighting the main findings for each U.S. city, click here.

Click here for a graphic displaying the overall findings per city or click here for the per capita findings graphic.

“This study shows that taking urgent action to reduce carbon pollution will save lives in cities across the United States,” said Frumhoff. “The government also has an obligation to help communities prepare for life in a world that’s heating up. This could include making air conditioning more available especially to those with low or fixed incomes, strengthening our health care system, and increasing awareness of heat-related health risks.”

“All heat-related deaths are potentially preventable,” said Ebi. “We need urgent investment in heat wave early warning and response systems and other options to protect the most vulnerable as temperatures continue to rise. Older adults, children and outdoor workers are among those populations particularly susceptible to higher temperatures. In the long term, urban planning must prioritize design changes that decrease urban heat islands and ensure our infrastructure is prepared for unprecedented temperatures.”

The numbers of avoided heat-related deaths in the analysis may be a conservative estimate, as they rely on current population data. Therefore, they cannot account for an aging population, increases in urbanization, exacerbation of the urban heat island effect, or other demographic factors that could change and contribute to added heat vulnerability.

*Please note that the high temperatures projected for 1-in-30-year events per city changes for the 1.5, 2 and 3 degrees Celsius scenarios.

The Union of Concerned Scientists puts rigorous, independent science to work to solve our planet’s most pressing problems. Joining with people across the country, we combine technical analysis and effective advocacy to create innovative, practical solutions for a healthy, safe, and sustainable future. For more information, go to www.ucsusa.org.