Manhattan, one of the places where climate change will kill people.

Shutterstock / Joshua HavivManhattan, one of the places where climate change will kill people.

Climate change is expected to boost homicidal heat waves in Manhattan, while cold snaps in the densely packed borough should become slightly less deadly.

Researchers from Columbia University and the Chinese Center for Disease Control and Prevention used climate models and two emissions scenarios to project seasonal patterns in temperature-related deaths in Manhattan. In all 32 of the scenarios developed by the researchers, the spike in summertime heat-related deaths was forecast to more than outweigh the decline in deaths caused by cold weather.

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Susie Cagle

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The study was published this week in the journal Nature Climate Change. “Monthly analyses showed that the largest percentage increases [in deaths] may occur in May and September,” the scientists wrote.

From Climate Central:

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The study found that heat-related mortality may rise 20 percent by the 2020s, and in some worst-case scenarios, it could increase by 90 percent or more by the 2080s, and the net temperature-related mortality, which includes the drop in deaths related to cold weather, could jump by a third compared to current levels. …

Some other studies have claimed that as heat wave-related deaths increase, they will be offset by a reduction in cold weather-related deaths, keeping the net change in mortality low or possibly even resulting in fewer temperature-related deaths per year. This study, however, finds the opposite to be true.

Extreme heat is already the No. 1 weather-related killer in the U.S., killing an average of 117 people per year during the 2003-2012 period. Hot temperatures can contribute to cardiovascular disease, aggravate respiratory illness, and cause heat stroke, among other life-threatening conditions.

Even a small amount of global warming can have a large effect on weather extremes, as recent studies have shown.

City dwellers can expect to be hit particularly hard by the heat waves that are growing in frequency around the world, as The Guardian reports:

Last year, the hottest summer since record-keeping began in the US, saw a string of days on which the temperature hit more than 37.7C (100F) in a number of US cities.

The week-long heatwave killed 82 people, according to figures compiled by the Associated Press.

In large metropolitan areas, such as New York, the impact of those temperature extremes are compounded by densely built-up areas. Cities such as Chicago, Cincinnati, Philadelphia and St Louis have also recorded sharp rises in deaths due to heart attacks and strokes during heatwaves, according to the draft of the National Climate Assessment, which was released last year.

“Urban heat islands, combined with an ageing population and increased urbanisation, are projected to increase the vulnerability of urban populations to heat-related health impacts in the future,” the assessment said.

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