‘Natural climate variations just can’t explain the observed recent global heat records, but man-made global warming can …’
It’s no accident that 13 out of the 15 warmest years on record have all occurred during the current century, according to climate researchers, who said there’s an “extreme likelihood” that the recent spate of warmth is caused by human-made climate change.
Without greenhouse-gas emissions from burning coal and oil, the odds that 13 out of the 15 warmest years ever measured would all have happened in the current, still young century are between 1 in 5000 and 1 in 170.000. Including the data for 2015, which came in after the study was completed, makes the odds even slimmer. The findings will be published in the journal Nature.
“2015 is again the warmest year on record, and this can hardly be by chance,” said Stefan Rahmstorf, with the Potsdam Institute for Climate Impact Research. The the new analysis enabled the research team to better separate natural climate variability from human-caused climate change.
“Natural climate variability causes temperatures to wax and wane over a period of several years, rather than varying erratically from one year to the next,” said lead-author Michael Mann, director of Earth System Science Center at Penn State . “That makes it more challenging to accurately assess the chance likelihood of temperature records,” Mann said.
With global attention focused on global warming after the Paris climate talks, Mann said it was important to do a study to address the question of “how unlikely it is that the recent run of record temperatures might have arisen by chance alone.”
The newly computed odds for experiencing the recent runs of record temperatures by chance, without accounting for human-caused greenhouse gases, are greater than odds previously reported in some media — between 1 in 27 million and 1 in 650 million – but they are still incredibly slim.
“Natural climate variations just can’t explain the observed recent global heat records, but man-made global warming can,” said Rahmstorf. “What is more, the anomalous global average warmth comes with substantial impacts.
“It has led to unprecedented local heat waves across the world – sadly resulting in loss of life and aggravating droughts and wildfires,” he said. “The risk of heat extremes has been multiplied due to our interference with the Earth system, as our data analysis shows.”