Last year would not have definitely been the warmest on record without an incredibly strong El Niño warming the Pacific Ocean, according to analyses done by two climate scientists.
Government scientists declared 2015 to be the warmest on record in early January, reaching 0.87 degrees Celsius above the 20th Century average. But scientists admit some of that warmth would not have been possible without El Niño — a naturally-occurring warming event.
Analyses from two climate scientists show that without the current El Niño warming, 2015 would have been statistically tied with 2014 for the warmest on record — despite the fact scientists are less than 50 percent sure 2014 is actually the hottest year recorded.
“The recent El Niño has contributed ~0.1 °C of warming to the GISS monthly temperature values throughout 2015,” according to one analysis by Thomas Cropper, a climate scientist with the libertarian Niskanen Center — a think tank that also promotes left-leaning solutions to global warming.
Gavin Schmidt, a climate scientist who heads up National Aeronautics and Space Administration’s (NASA) Goddard Space Flight Center, estimated last year’s El Niño added 0.07 degrees Celsius to the global average temperature, meaning it would have only been 0.8 degrees above 20th Century average, according to the environmentalist blog Carbon Brief. That means 2015 would have only been 0.06 degrees warmer than 2014.
“This is still the warmest year in the NASA record, albeit by only 0.06C – less than the margin of error associated with estimates of global temperature,” Carbon Brief noted.
Both analyses mean 2015’s average global temperature could have been anywhere from 0.03 to 0.06 degrees Celsius warmer than 2014 without El Niño — well within the margin of error. Without El Niño, 2015’s average global temperature would have been statistically indistinguishable from 2014.
Last year, NASA scientists declared 2015 was the warmest on record, but they were only 38 percent sure that was actually the case because the difference between that year’s temperature and 2010’s was within the margin of error. The National Oceanic and Atmospheric Administration (NOAA) was only 48 percent sure 2014 was the warmest on record.
NASA and NOAA were heavily criticized for claiming 2014 as the warmest on record when they were so unsure. Critics pointed out 2014 basically continued to decade-long trend in the surface temperature record.
“With 2014 essentially tied with 2005 and 2010 for hottest year, this implies that there has been essentially no trend in warming over the past decade,” Judith Curry, a climate scientist at the Georgia Institute of Technology said last year.
“This ‘almost’ record year does not help the growing discrepancy between the climate model projections and the surface temperature observations,” Curry said.
Both Cropper and Schmidt used their data, however, to argue human activities were the main driver of 2015’s “record” warmth.
“El Niño helped, but the record came from the overall warming trend. Simply put, there is one major reason behind 2015 temperatures – global warming,” Cropper wrote.
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