- Bishop Hill blog

A new paper by Kevin Cowtan et al claims that the divergence of models and observations is not as big as we thought.

Global mean temperatures from climate model simulations are typically calculated using surface air temperatures, while the corresponding observations are based on a blend of air and sea surface temperatures. This work quantifies a systematic bias in model-observation comparisons arising from differential warming rates between sea surface temperatures and surface air temperatures over oceans. A further bias arises from the treatment of temperatures in regions where the sea ice boundary has changed. Applying the methodology of the HadCRUT4 record to climate model temperature fields accounts for 38% of the discrepancy in trend between models and observations over the period 1975-2014.

It sounds a bit odd to me, but I don't have a copy as yet, so I'm going to hold off further comment for the minute. One assumes though that even if the findings are sound the divergence of satellite temperatures from the models is unaffected.

Update on Jul 30, 2015 by

Bishop Hill

Thanks to readers who have sent the paper along. Here's what the authors have done:

Global averages of the observational temperature records are typically compared to near surface air temperature from an ensemble of climate model simulations...most studies have used the surface
air temperature field from models rather than blended land-ocean temperatures...A true like-with-like comparison would involve blending the air and sea surface temperature fields from the models in a manner consistent with the observational records. The purpose of this work is to evaluate the impact of comparing air temperatures from models with the blended observational data, and to establish guidelines for the determination of blended temperature comparisons.

This seems unexceptionable to me.