Is This Heat Wave Evidence of Global Warming?

Beachgoers enjoying the hot weather at Crissy Field on Sunday. Photo: Marin Favier.

Another heat wave is upon us. It seems like there have been a lot of heat waves this summer. We in the Bay Area were sweating for a few days back in August; New York City had the hottest summer on record; Russia suffered through horrible heat and fires. Are all these heat waves the result of global warming?

Several climate studies have found that heat waves are likely to become more frequent—and hotter—as the earth warms up. In this recent paper out of Stanford, two researchers ran several different climate models to see how a 1 degree Celsius increase in average global temperature would affect heat waves over the next 30 years. They found that even with this relatively optimistic increase in average temperature, heat waves are predicted to happen more frequently—especially here in California.

However, we cannot say that this week’s hot weather a result of global warming. Any single extreme event—a heat wave or a hurricane—cannot be attributed to climate change. One event is just one data point. To know whether there is a trend, we have to look at a whole cloud of data: heat wave incidence across several years. But, 2010 is shaping up to be a really hot year. So far, heat records have been set in 17 countries since the start of 2010.

Heat waves have some serious consequences. Heat stresses and kills organisms—its effects in the marine intertidal have been particularly well documented, affecting seaweed, mussels, barnacles, and more. Heat can make trees drop their leaves, and can damage and kill crops, creating economic havoc. And people, particularly the elderly, can perish, as a result of dehydration and hypothermia.


As heat waves become more and more frequent, will people see them as evidence that global warming is happening? Or will people just get accustomed to the hot weather?

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