The Biggest Question About Climate Change Isn’t ‘If’ or ‘When.’ It’s ‘How Abrupt?’ - The Washington Post

It has been quite the week for climate change news: We’ve learned that scientists can now quantify the United States’ expected levels of inundation by rising seas, that droughts in the Amazon could triple, and much more.

But the most troubling research — depending, that is, on how you interpret it — may have appeared in a less-noticed, first-of-its-kind study just published in the influential Proceedings of the National Academy of Sciences.  In it, the researchers attempted something that seems never to have been successfully done before. Namely, they mined the data from a large suite of computerized climate change simulations, or models, to determine how often they produced abrupt and disruptive changes in a few decades or even less — surely the most feared impact of climate change.

The result — that out of 37 abrupt changes detected in these climate simulations, fully 18 of them occurred at temperature levels less than 2 degrees Celsius of warming — is simultaneously dramatic and yet also difficult to assess.  Models, after all, are mathematically sophisticated simulacra that embed scientists’ best current physical understanding of how the Earth system and its components work, but still should not be confused with reality.

Nonetheless, the authors — led by Sybren Drijfhout, a professor at the Royal Netherlands Meteorological Institute — assert that their results represent a sign of how unstable the future could really be, even before we reach warming levels of 2 degrees Celsius above pre-industrial levels (often thought of as a kind of guardrail in international climate negotiations).  “It is likely that the Earth system will experience sharp regional transitions at moderate warming,” they write, “although the prediction of any particular event has a very high uncertainty.”

Read more at The Biggest Question About Climate Change Isn’t ‘If’ or ‘When.’  It’s ‘How Abrupt?’