More of these will be part of global warming's impacts, scientists predict.
The name of the study by Erich M. Fischer and Reto Knutti is a mouthful—
"Anthropogenic contribution to global occurrence of heavy-precipitation and high-temperature extremes." Translation: global warming is causing weather extremes. Just as scientists have been predicting for at least a quarter century.
While this isn't the first study to make such a connection between extreme weather events and global warming, Fischer and Knutti are the first to forecast how those extremes may be transformed by future global warming. Not a pretty picture.
The authors acknowledge that it is challenging to tie a specific extreme weather event to human-caused global warming effects. This is so in part because of deficiencies in climate models and observational uncertainty. But the study's authors are confident of their fresh methodology. They used "computer analyses of what the climate would be like if the Industrial Revolution had never happened," Justin Gillis reports:
The moderate global warming that has already occurred as a result of human emissions has quadrupled the frequency of certain heat extremes since the Industrial Revolution, scientists reported Monday, and they warned that a failure to bring greenhouse gases under control could eventually lead to a 62-fold increase in such heat blasts.
The planetary warming has had a more moderate effect on intense rainstorms, the scientists said, driving up their frequency by 22 percent since the 19th century. Yet such heavy rains could more than double later this century if emissions continue at a high level, they said.
Many people point out that weather extremes are nothing new, and Fischer agrees. But, as he points out in an interview about the study published Monday in the journal
Nature Climate Change, "[T]he odds have changed, and we get more of them.”
He and Knutti conclude:
Already today 75% of the moderate hot extremes and about 18% of the moderate precipitation extremes occurring worldwide are attributable to warming, of which the dominant part is extremely likely to be anthropogenic. The fraction increases nonlinearly with further warming such that the probability of hot extremes at 2°C, for example, is double that at 1.5°C global warming. With every degree of warming it is the rarest and the most extreme events—and thereby the ones with typically the highest socio-economic impacts—for which the largest fraction is due to human-induced greenhouse gas emissions.
Currently, tropical island nations, "which typically have high vulnerability and low adaptive capacities," face the worst impacts. For now.