A claim by some climate change skeptics that new NASA satellite measurements of global average temperatures over land since the end of the El Nino suggest that record-breaking high temperatures in 2015 were not caused by human emissions has sparked controversy as anthropogenic global warming (AGW) advocates push back.
According to David Rose, in an article published on November 27, 2016, on the Daily Mail, a drop in global average temperatures over land by one degree Celsius since the end the El Nino effect in the middle of the year, adds to mounting evidence against the AGW theory.
This fall in temperatures, the biggest and steepest fall on record, according to Rose, suggests that the El Nino weather phenomenon, and not human carbon emissions, was responsible for 2015 being the hottest on record.
El Nino has now been replaced by the La Nina phenomenon which is causing a drop in global average temperatures over land, according to Rose. The cooling effect of La Nina has had worldwide impact, with global average temperatures taking the “biggest and steepest plunge on record,” Rose added.
And although 2016 is still expected to be the hottest year on record, “it is almost certain” that lower temperatures will be measured over the oceans in subsequent years, according to Rose. This could seriously undermine the AGW theory.
Rose emphasized in his article that El Nino is a complex natural weather cycle that takes place every few years and that it has nothing to do with human carbon emissions. But the warming affects large areas of the world, with the 2015-2016 El Nino being probably the strongest since accurate measurements began to be taken.
But supporters of AGW theory have denied the claims contained in Rose’s article.
In a December 5, 2016, article in the Guardian by environmental scientist Dana Nuccitelli, titled “Fake news tries to blame human-caused global warming on El Niño,” human carbon pollution is to blame for the increasing global average temperatures. Without human-caused global warming, we would not have seen record-breaking average temperatures in recent consecutive years.
Nuccitelli dismissed the claim that El Nino is the primary cause of the recent run of record high global temperatures, arguing that the NASA satellite measurements allegedly showing a drop in global average temperatures over land were actually estimates of the temperature of the lower atmosphere above areas of the Earth’s surface covered by land masses and not temperatures on the surface of the Earth where humans live.
The environmental scientist accused climate change skeptics of cherry-picking data, pointing out that while satellite data extends only as far back as 1979, global surface temperature data go back as far as 1880. But Rose and other climate change skeptics cited only portions of the data dating back to 1997 and based their claim of “plummeting” global average temperatures only on the relatively cool month of October 2016, which, according to Nuccitelli, was even “hotter than every month on record prior to 1998.”
Although the scientist argued that human carbon emissions are the primary cause of global temperature rise, he admitted that El Nino contributed to the recent spike in global average temperature.
“Human carbon pollution is heating the Earth incredibly fast. On top of that long-term human-caused global warming trend, there are fluctuations caused by various natural factors. One of these is the El Niño/La Niña cycle,” Nuccitelli said.
“The combination of human-caused warming and a strong El Niño event are on the verge of causing an unprecedented three consecutive record-breaking hot years, “he continued. “Simply put, without global warming we would not be seeing record-breaking heat year after year.”
“In fact, 2014 broke the temperature record without an El Niño assist, and then El Niño helped push 2015 over 2014, and 2016 over 2015.”
Dr. Gavin Schmidt, who heads NASA’s climate division, agreed with Nuccitelli, insisting that anthropogenic factors (man-made factors) were the primary cause of the recent run of record temperatures, and not El Nino.
According to Schmidt, data shows that 2015 would have been the hottest year ever recorded even if El Nino had not contributed to warming.
“The reason why (2015 was) such a warm record year is because of the long-term underlying trend, the cumulative effect of the long-term warming trend of our Earth,” the NASA scientist said, according to the Daily Mail. “This was ‘mainly caused’ by the emission of greenhouse gases by humans.”
But in his Daily Mail article, Rose had cited Judith Curry, climate scientists at the Georgian Institute of Technology and president of the Climate Forecast Applications Network, who disagreed with both Nuccitelli and Gavin.
“I disagree with Gavin. The record warm years of 2015 and 2016 were primarily caused by the super El Nino.”
According to Curry, data suggests that in the years between the 1998 El Nino event and the 2015 El Nino event, the rate of global warming was lower than estimated by AGW models.
She concluded that climate scientists would have to wait at least another five years to confirm their claim that man-made factors, rather than natural El Nino, is the primary cause of to confirm which of the two factors — natural El Nino and man-made factors — was more responsible for the recent temperature spikes, according to Express.
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