Wednesday, November 25, 2015

Global Warming Key Driver of 2015’s Record Heat

The gray line on this graph shows observed surface temperatures from 1880 to 2015. The red line shows the effective temperature forcing of greenhouse gases and aerosols (converted to CO2), and the blue line shows the forcing from both those manmade sources and natural factors, like solar radiation. Early on in the temperature record, the red and blue lines diverge because natural factors meant the full impact of greenhouse gases on temperatures wasn't being felt, but in recent years, the two lines match closely, showing how much greenhouse gases are dominating global temperatures. 2015 is slightly above the red line because of a small push from El Niño as well as even smaller contributions from solar radiation and random weather variations. (Credit: Click to Enlarge.
It is virtually certain that 2015 will be the warmest year on record, with one of the strongest El Niños ever recorded combining with manmade warming to send global temperatures soaring.  But which of these is more responsible for the record heat this year?

Global warming fueled by the buildup of heat-trapping gases in the atmosphere is the overwhelming contributor, according to a new analysis by scientists involved with Climate Central’s World Weather Attribution program and at the University of Reading.

That analysis, which broke down the effects of a number of different possible influences on the global temperature, found that El Niño provided only a relatively small, though still noticeable, assist.  And with 2015 not even officially yet in the record books, 2016 could see even more of a warming boost from El Niño, thanks to the delayed effect it has on temperatures.

“2015 is a climate milestone in several ways.  Atmospheric carbon dioxide has now passed 400 [parts per million] for the foreseeable future.  It will also be the warmest year on record, primarily because of anthropogenic emissions of greenhouse gases, with CO2 being the main culprit,” Ed Hawkins, a climate scientist at the University of Reading, said in an email.

Read more at Global Warming Key Driver of 2015’s Record Heat

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