Publication Date June 30, 2017

Extreme Heat Is Defining Climate Change

United States
Image: Climate Central

The lasting legacy of climate change will be heat. The land, the oceans, all of it. It’s the tie that binds and while the global average temperature is the defining metric, the increasing incidence of heat waves and longer lasting extreme heat is how the world will experience it.

All eight papers dealing with extreme heat events in this year’s Bulletin of the American Meteorological Society’s attribution report show a clear climate change signal that made them more likely, more hot or both. In fact, of the 22 studies scientists have submitted to the annual review over the past four years, only one didn’t find that climate change increased the odds or severity of extreme heat.

"​Global warming is the most obvious, well-documented effect of ​climate change,” Stephanie Herring, a climate scientist at the National Oceanic and Atmospheric Administration and organizer of this year’s attribution issue, said. “As a result, the signal is very strong so we can more easily detect it amongst noise of natural variability compared to other types of extreme events."

In the case of a strong signal, 2014 stands out as particularly notable. It was the hottest year on record, though this year is on track to top last year’s record (and signs are already pointing to 2016 continuing the record heat parade).

The lift in background temperatures makes extreme heat more likely. “The underlying processes that relate climate change to heat wave intensity and frequency are fairly straightforward to understand: if you increase the average temperature by even a modest amount, then it turns out that you dramatically increase the area under the extreme positive ‘tail’ of the distribution,” Michael Mann, a climate scientist at Penn State who wasn’t involved in any of the new studies, said in an email.