Yale's Kai Chen reports that air conditioning saved an average of 5,267 lives a year in the United States from 2010 to 2020, nearly 58,000 over the decade. Extra cooling, he says, does not save more lives. Many places treat 24 degrees Celsius (75 degrees Fahrenheit) as a reasonable indoor limit, and residual heat risk remains on the hottest days. United Nations figures project heat-trapping gas from cooling rising in about 25 years from 4.5 billion to 7.2 billion tonnes.
Kai Chen of the Yale School of Public Health reports that air conditioning saved an average of 5,267 lives a year in the United States from 2010 to 2020, nearly 58,000 over the decade. With Chen as senior author, the same average is put at 5,267 lives saved a year.[1], [2]
The most lives saved were in Arizona, Florida, Texas, Louisiana and southern Nevada, Alabama and Mississippi. More than a dozen northern states, from Washington to Maine, had fewer than 10 lives a year saved. US cooling degree days, a measure of how much cooling buildings need, have risen since 1990 by 28 per cent.[1]
Chen says using more air conditioning than needed does not save more lives. Many places already use 24 degrees Celsius (75 degrees Fahrenheit) as a reasonable indoor limit. The protective effect levels off once use passes a certain point, and residual heat risk remains on the hottest days even with air conditioning in use. United Nations figures project heat-trapping gas from cooling rising in about 25 years from 4.5 billion to 7.2 billion tonnes, and electricity demand from cooling is expected to triple. Chen says more than half the cases the researchers looked at could be considered overuse.[1], [2]
