Nighttime temperatures are warming faster

**updated June 2021**

More impact from climate change–at one point this month (July 2018), “more than 100 million people” in the United States were under heat warnings or advisories.  While high daytime temperatures and humidity were most noticeable, it was the nighttime temperatures that were having the greatest impact.

“Nationwide, summer nights have warmed at nearly twice the rate of days”; overnight low temperatures have increased an average of 1.4 degrees F since 1895; daytime temperatures have increased an average of 0.7 degrees per century.  And, nighttime temperatures have warmed faster than days in the winter, spring, and fall as well.

This pattern is expected to continue …

While the change in temperatures may seem small, the consequences are very large.

Most years, heat waves kill more people in the U.S. than any other natural disaster including floods and hurricanes.  “The combination of high daytime and high nighttime temperatures can be really lethal because the body doesn’t have a chance to cool down during the nighttime hours.”  And, “the risks are higher in places where temperatures have historically been cooler.”  Older people, the sick, young children, outdoor workers, and the homeless are particularly at risk.  In cities, where the heat island effect exacerbates high temperatures, it is often the poor and/or minority residents who are more likely to live in the hotter areas.

Yes, air conditioning can help.  But, air conditioners work by sending hot air outside–where it can add to the heat island effect in urban areas.  Plus, air conditioning is a major player in climate change globally, and increased air conditioner use during heat waves is a factor in power failures.

This is another impact of climate change that is real and is happening today–read the article, see the graphs (Kendra Pierre-Louis and Nadja Popovich, New York Times, July 11, 2018).

For more information, search the Science Primary Literature database.

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