The Washington Post

Study: Home air conditioning cut premature deaths on hot days 80 percent since 1960

As winter begins to tighten its grip on much of the United States, air conditioning doesn’t seem like much of a survival strategy. But a new study has found that home air conditioning played a key role in reducing American death rates over the past half-century, by keeping people cool on extremely hot days.

The installation of air conditioning in American homes is the reason why the chances of dying on an extremely hot day fell 80 percent over the past half-century, according to an analysis by a team of American researchers.

The findings, based on a comprehensive analysis of U.S. mortality records dating from 1900, suggests the spread of air conditioning in the developing world could play a major role in preventing future heat-related deaths linked to climate change. Very few U.S. homes had air conditioning before 1960; by 2004, that figure had climbed to 85 percent.

A team of researchers from Tulane University, Carnegie Mellon University, the National Bureau of Economic Research and the Massachusetts Institute of Technology examined patterns in heat-related deaths between 1900 and 2004. The group found that days on which temperatures rose above 90 degrees Fahrenheit accounted for about 600 premature deaths annually between 1960 and 2004, one-sixth as many as would have occurred under pre-1960 conditions.

“It’s all due to air conditioning,” said MIT environmental economics professor Michael Greenstone, one of the paper’s co-authors, adding that factors including increased electrification and health-care access did not affect heat-related mortality.

The likelihood of a premature death on an extremely hot day between 1929 and 1959 was 2.5 percent, the academics found, dropping to less than 0.5 percent after 1960. The paper, which is under review at an academic journal, compared days on which temperatures exceeded 90 degrees Fahrenheit with days when they ranged between 60 and 69 degrees Fahrenheit.

Matthew E. Kahn, an economics and public policy professor at UCLA’s Institute of Environment, called the study “a very strong paper” that could show one strategy for adapting to increasingly frequent bouts of warmer weather. The U.N. Intergovernmental Panel on Climate Change issued a report this year linking the increase in heat waves to human-generated greenhouse gas emissions, predicting the frequency of these events will increase in the coming decades.

“We have to begin to wake up to the new normal,” Kahn said. “Rational people have to learn how to duck and take action so we don’t get rolled by Mother Nature.”

The study’s results could be particularly important for nations such as India, where only a small portion of the population has residential air conditioning. The typical person in India experiences 33 days per year where the temperature rises above 90 degrees Fahrenheit; that could increase by as much as 100 days by the end of the century, according to some climate projections.

Anand Patwardhan, a visiting professor at the School of Public Policy at the University of Maryland in College Park, said he expects home air conditioning to become more common in India, but not as a conscious response to global warming.

“While it is certainly the case that residential air-conditioning helps in reducing mortality due to temperature extremes, the rapid growth of air-conditioning in the past is perhaps more due to rising incomes and increasing affordability of air-conditioning,” he wrote in an e-mail.

The spread of air conditioning has one obvious problem, Greenstone noted, since many of these units will likely be powered by fossil fuels and will therefore increase the world’s carbon output.

“The painful part of that is the solution involves more energy consumption,” he said. “And that is going to exacerbate the problem of increased temperatures.”

Andrew Steer, president of the World Resources Institute, said that although there is no question about “air conditioning growing in leaps and bounds in developing countries with rising temperatures,” policymakers also need to explore “ecological” adaptation strategies that yield environmental benefits instead.

Indian Institute of Technology professor Ambuj Sagar wrote in an e-mail that the world should focus on improving appliance efficiency in the face of warmer weather.

“To me, if there is any policy relevance of this study, it is that the developing countries, in their drive for a comfortable life (which will also help adapt to hotter temperatures) are following the same pathway that their industrialized-country counterparts because they don’t have any other pathway available,” Sagar wrote.

Juliet Eilperin is The Washington Post's White House bureau chief, covering domestic and foreign policy as well as the culture of 1600 Pennsylvania Avenue. She is the author of two books—one on sharks, and another on Congress, not to be confused with each other—and has worked for the Post since 1998.



Success! Check your inbox for details. You might also like:

Please enter a valid email address

See all newsletters

Show Comments

Sign up for email updates from the "Confronting the Caliphate" series.

You have signed up for the "Confronting the Caliphate" series.

Thank you for signing up
You'll receive e-mail when new stories are published in this series.
Most Read



Success! Check your inbox for details.

See all newsletters

Your Three. Videos curated for you.
Play Videos
How to make Sean Brock's 'Heritage' cornbread
New limbs for Pakistani soldiers
The signature dish of Charleston, S.C.
Play Videos
Why seasonal allergies make you miserable
John Lewis, 'Marv the Barb' and the politics of barber shops
What you need to know about filming the police
Play Videos
The Post taste tests Pizza Hut's new hot dog pizza
5 tips for using your thermostat
Michael Bolton's cinematic serenade to Detroit
Play Videos
Full disclosure: 3 bedrooms, 2 baths, 1 ghoul
Pandas, from birth to milk to mom
The signature drink of New Orleans

To keep reading, please enter your email address.

You’ll also receive from The Washington Post:
  • A free 6-week digital subscription
  • Our daily newsletter in your inbox

Please enter a valid email address

I have read and agree to the Terms of Service and Privacy Policy.

Please indicate agreement.

Thank you.

Check your inbox. We’ve sent an email explaining how to set up an account and activate your free digital subscription.