Links between global warming and massive heat waves

What science can tell us about the links between global warming and massive heat waves, WP, By Chris Mooney July 21 The United States is witnessing a massive, dangerous heat wave, as a huge system of high pressure covers the central part of the country. It’s a big enough deal that yesterday President Obama even tweeted about it, including a map showing the maximum heat index in some parts of the Midwest and Southeast reaching 110 or 115 degrees on Saturday.

Here in Washington, temperatures could break 100 degrees Friday or over the weekend.

[D.C.’s summer heat is rapidly becoming more oppressive, analysis finds]

This will, inevitably, lead to much talk of climate change in the coming days. So it’s important to separate the scientific wheat from the chaff and figure out what science can, and can’t, reliably say about the link between an event like this and a warming planet — especially in a year that, on a global scale, has shattered past temperature records for six out of the last six months.

[June sets another global temperature record, extending a blazingly hot year]

And the gist is that when it comes to extreme heat waves in general — heat waves that appear out of the norm in some way, for instance in their intensity, frequency, or duration — while scientists never say individual events are “caused” by climate change, they are getting less and less circumspect about making some connection….

[It’s official: We can now say global warming made some weather events worse]……we’ve definitely already had changes in not only “long-term mean conditions,” but in heat waves themselves. The U.S. National Climate Assessment found that U.S. heat waves have already “become more frequent and intense,” that the U.S. is shattering high temperature records far more frequently than it is shattering low temperature records (just as you’d expect), and that it is seeing correspondingly fewer cold spells.

As for future projections, meanwhile, the assessment added that “Climate models project that the same summertime temperatures that ranked among the hottest 5% in 1950-1979 will occur at least 70% of the time by 2035-2064 in the U.S. if global emissions of heat-trapping gases continue to grow.”…..

“With every heat wave, probably the number one question is, is it climate change, or is it not? Well the answer is, it’s both,” said Texas Tech University climate scientist Katharine Hayhoe on a press call Thursday. “We get heat waves naturally, but climate change is amping them up, it’s giving them that extra energy, to make them even more serious, and have even greater impacts.” https://www.washingtonpost.com/news/energy-environment/wp/2016/07/21/what-science-can-tell-us-about-the-links-between-global-warming-and-massive-heat-waves/?wpisrc=nl_green&wpmm=1