Why Summer in the City Will Get Deadlier

As the climate warms, heat-related deaths are almost certain to increase in cities like New York—unless we take steps to adapt to global warming

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Heat waves will take more lives in New York as the climate warms

Heat kills. In 1995 five days of stifling heat led to more than 750 deaths in Chicago, as mostly elderly and sick people died in their oven-like apartments. In 2003, a record heat wave struck much of Europe, which led to as many as 70,000 additional deaths due in part to heat. France, which was unused to lingering heat in the summers and which mostly lacks air-conditioning, was hardest hit. Thousands of elderly people died during the heat wave in August of that year, so many that some bodies were left unclaimed for weeks. Undertakers in Paris ran out of space to store all the corpses.

So you can imagine that researchers — and officials in big cities — are worried about the effect of killer heat waves in the future, supercharged by climate change. They have reason to fear. A new study in the journal Nature Climate Change by researchers at Columbia University’s Earth Institute and Mailman School of Public Health looked at Manhattan and found that temperature-related deaths could rise by some 20% by the 2020s and — if worst-case scenarios hold — could rise by more than 90% by the 2080s. And that’s despite the fact that rising temperatures in the winter would be expected to reduce deaths from cold. Heat in a hot and crowded world could be that deadly.

Study co-author Radley Horton, a climate scientist at the Earth Institute, said in a statement:

This serves as a reminder that heat events are one of the greatest hazards faced by urban populations around the globe.

The Nature Climate Change study is hardly the first to try to project how rising temperatures could impact heat-wave-related deaths, but it is unusually detailed, thanks in part to the minute weather data kept in the city. Monthly average temperatures in New York’s Central Park rose 3.6ºF between 1901 and 2000 — significantly more than the global and U.S. average. That’s likely due in part to the urban-heat-island effect: the concrete of a major city holds in heat, causing temperatures to rise and stay hotter than in surrounding, greener areas, especially at night. That’s one reason big cities like New York will be uniquely vulnerable to longer and stronger heat waves in the future.

Depending on climate models and future action on carbon emissions, temperatures can be expected to rise 3.3ºF to 4.2ºF by midcentury, and 4.1ºF to 7.1ºF by the 2080s. The best-case scenario projects an increase of temperature-related deaths of about 15% over a 1980s baseline of 370 heat deaths and 340 deaths from cold. The worst case would see an increase of over 30%, which would translate to more than 1,000 deaths.

That’s not inevitable, though. Even if we fail to curb warming, cities can reduce heat-related deaths through smart interventions, including planting roof-top gardens to cut the urban-heat-island effect, and providing air-conditioned cooling centers for the elderly and the needy. Indeed, New York and other cities have already taken those steps — Chicago in particular learned after the deadly 1995 heat wave — which is one reason why heat-related deaths in the city actually went down over the second half of the 20th century, even as temperatures increased.

Smart planning can cope with climate change, but an endless summer would tax all our resources — and not just the air-conditioning bill.