Friday, December 14, 2018

Forecasts of Old Climate Models

Zeke Hausfather, now at Carbon Brief, shared the poster he's presenting today at the AGU Fall Meeting in DC.
Click on the image to get a fuller 
presentation of the Hansen graphs.

I assume he put the actual forcings that occurred into Hansen's projections, instead of what Hansen assumed.

I don't know what models Zeke's considering here, but there were only a few big models that cover that time period -- see the IPCC ARs of the period.

It will be interesting to see how much the observations of the 2010s bring the agreement back in line from the 'noughts. You can get a sense of that from Ed Hawkins' monthly update comparing observations to CMIP5 models; they've come back up after the lows around 2010:

Added about one hour later:

I asked ZekeH on Twitter how he corrected model projections for the actual emissions, instead of the assumed emissions. He wrote:


Layzej said...

we evaluated models on the basis of the ratio of model warming to model forcings, which mostly normalized for misspecified future forcings (see the bottom panel of the figure).

So the top graph is showing divergence between projected vs observed temps but the bottom graph shows close agreement wrt forcing vs warming?

David Appell said...

Well, the bottom graph stops in 2010.

Layzej said...

The bottom graph stops at 1.7 w/m^2... I think Hansen just presumed we'd have emitted more ghg by now.

Layzej said...

This pretty cool and is also from Zeke: