Both globally and in California, 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.
The average global temperature for 2015 is well ahead of last year, the current titleholder of warmest year. October provided a particularly large boost, with a temperature that was above average by more than any other single month in the past 135 years. By NASA’s reckoning, October was more than a full degree Celsius (nearly 2°F) above the average from 1951-1980, the first month that has ever happened.