A new study came out today that seems to be a pretty big deal, though it's not my area of expertise. A team of scientists narrowed estimates of climate sensitivity. In The Precipice, Toby Ord notes that uncertainty about things like this increases the probability we should place on such risks. Does anyone know how much this study should lower our credence (if at all)?
Here are the "Key Points" from the study:
● We assess evidence relevant to Earth’s climate sensitivity S: feedback process understanding, and the historical and paleo-climate records.
● All three lines of evidence are difficult to reconcile with S < 2 K, while paleo evidence provides the strongest case against S > 4.5 K. 48
● A Bayesian calculation finds a 66% range of 2.6-3.9 K, which remains within the bounds 2.3-4.5 K under plausible robustness tests.
AR6, for the uninformed like me.
Very useful comment — thanks.
How do these tail values compare with your previous best guess?
I suppose they're roughly in line with my previous best guess. On the basis of the Annan and Hargreaves paper, on median BAU scenario the chance of >6K was about 1%. I think this is probably a bit too low because the estimates that ground that were not meant to systematically sample uncertainty about ECS. On the WCRS estimate, the chance of >6K is about 5%. (Annan and Hargreaves are co-authors on WCRS, so they have also updated).
One has to take account of uncertainty about emissions scenarios as well