Heat waves in Eastern US will become deadlier, study says

Nov 08, 2013

Wu J, Y Zhou, Y Gao, JS Fu, BA Johnson, C Huang, YM Kim, Yang Liu. 2013. Estimation and uncertainty analysis of impacts of future heat waves on mortality in the Eastern United States. DOI:10.1289/ehp.1306670

Synopsis by Brian Bienkowski

Heat waves will kill about 10 times more people in the Eastern United States in 45 years than they did at the turn of this century, according to a new projection from researchers. The study builds on previous research that predicts as climate change spurs more frequent heat waves, there will be more heat-related deaths.

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Heat waves will kill about 10 times more people in the Eastern United States in 45 years than they did at the turn of this century, according to a new projection from researchers.

The study builds on previous research that predicts as climate change spurs more frequent heat waves, there will be more heat-related deaths. It is the first study to project future heat wave deaths across an entire region.

"Estimates suggest that mortality risks from future heat waves may be an order of magnitude higher than in 2002-2004,” says the study, which was published online this week in the journal Environmental Health Perspectives.

The researchers used two climate change projections for the Eastern third of the United States. Both assume that emissions will increase, but at different rates. One scenario projects “low-medium” greenhouse gas emissions and one projects a “more extreme” scenario, similar to today’s rate. Under the “low-medium” scenario, heat wave-related deaths would increase by 1,403 per year compared with 3,556 under the more dire projection, according to the study.

An estimated 187 people in the Eastern United States died of causes related to heat waves per year during 2002-2004. Nationwide, about 660 people die each year from heat waves, according to the U.S. Centers for Disease Control and Prevention.

The large disparity between the projections suggests “curtailing emission will have a great impact on the reduction of heat wave mortality in the future,” wrote the authors, led by Emory University environmental health scientists.

The scientists found that heat waves will be 3.5 to 6.4 times more frequent from 2057 to 2059 compared with 2002 to 2004.

Some places will have it worse than others: 10.4 percent of the 1,700 counties in the study are projected to have more than four heat waves per year under the lower emissions scenario, and 26.5 percent would have more than four heat waves per year under the increased emissions scenario.

Southern states such as Florida, Georgia and Louisiana, and those on the coast, such as Massachusetts, New York and New Jersey, would have the biggest jump in deaths, according to the study.

“Effective mitigation and adaptation measures will be crucial to reduce the potential for catastrophic outcomes, particularly in the most vulnerable geographic regions,” the authors wrote.

Air temperature is projected to increase between 3.2 and 11.52 degrees Fahrenheit over the next 90 years, increasing the frequency, intensity and duration of U.S. heat waves, according to the Intergovernmental Panel on Climate Change. Heat waves cause spikes in body temperature, which can cause brain and organ damage, and, in severe cases, death. The elderly, poor, children and outdoor workers are most at risk.

The study is limited since the Eastern United States is largely urban. City temperatures are generally higher, driving up projected deaths. In addition, the researchers didn’t look at non-heat wave days that could be hot enough to cause deaths.

For the study, the scientists used scenarios developed by the IPCC, one “low-medium scenario of climate change that assumes moderate emissions and use of a range of technologies and strategies for reducing greenhouse gas emissions, and the more extreme RCP8.5 scenario, which assumes fossil fuel intensive energy consumption with increasing greenhouse gas emissions,” similar to today’s rate.