Friday, June 30, 2017

Global Warming Tipped Scales in Europe’s Heat Wave

No surprise. If you have half a cup of hot water and half a cup of cooler water, if you add the same amount of hot water to each, the one that was warmer to start with will continue to be the warmer one.

Andrea Thompson By Andrea Thompson
June 29, 2017

Global warming gave a clear boost to the searing temperatures that blanketed Western Europe earlier this month — a heat wave that helped fuel deadly wildfires in Portugal.

The greenhouse gas-driven warming of the atmosphere has made the intensity and frequency of such extreme heat up to 10 times as likely, according to a new analysis from researchers working with Climate Central’s World Weather Attribution program and several outside partners.

It is the latest such attribution analysis to show that the warming that has occurred over the last century — nearly 2°F (1°C) — has already had a clear influence on such extreme heat events.

“Global warming has already put a thumb on the scales; it’s already tipped the odds,” Noah Diffenbaugh, a Stanford University climate scientist who wasn’t involved with the work, said.


To evaluate the role of global warming in the recent heat wave, the researchers used both historical temperature observations and climate models to see how the odds of such an event have changed over time and to compare the odds in a climate with and without warming, respectively.

They found that the likelihood of such a heat wave had at least doubled across the region and was up to 10 times more likely in the worst-hit places, Spain and Portugal. What was once a rare heat event can now happen every 10 to 30 years, and is more likely to happen earlier in the summer.

The findings fit with other studies, including one by Diffenbaugh that found that record heat was both more likely and more severe over 80 percent of the part of the globe with good enough observational data.

That trend toward more and more severe heat will continue, especially if the heat-trapping greenhouse gases that are driving global temperature rise aren’t curtailed.






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