The Bob-bot strikes again
Apr 8, 2016
Bishop Hill in Climate: Ward, Climate: sensitivity


At the end of last year, Bob Ward had this to say about a new paper on climate sensitivity:


A new paper on climate sensitivity that @mattwridley and other peddlers of denial will pretend does not exist:

— Bob Ward (@ret_ward) December 31, 2015


In fact, far from being ignored by the sceptic community, the paper in question, by Marvel et al., turned out to be something of a car-crash and was the source of steady stream of more-or-less amused blog posts in the months that followed.

This morning I couldn't help but wonder if someone has replaced Bob with a bot, preprogrammed to issue identical tweets in the response to any new paper on climate sensitivity:


New paper on climate sensitivity that @mattwridley and other climate change 'sceptics' will pretend does not exist:

— Bob Ward (@ret_ward) April 8, 2016


The paper, by Tan et al., looks as though it's a GCM-with-observational-constraints effort. 

Global climate model (GCM) estimates of the equilibrium global mean surface temperature response to a doubling of atmospheric CO2, measured by the equilibrium climate sensitivity (ECS), range from 2.0° to 4.6°C. Clouds are among the leading causes of this uncertainty. Here we show that the ECS can be up to 1.3°C higher in simulations where mixed-phase clouds consisting of ice crystals and supercooled liquid droplets are constrained by global satellite observations. The higher ECS estimates are directly linked to a weakened cloud-phase feedback arising from a decreased cloud glaciation rate in a warmer climate. We point out the need for realistic representations of the supercooled liquid fraction in mixed-phase clouds in GCMs, given the sensitivity of the ECS to the cloud-phase feedback.

I can't imagine quite how large the gap between a 5.7°C-ECS climate simulation and the historical temperature record is going to be. I wonder what fairy story will be conjured up to explain that away.

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