We* are a group of researchers who just published a paper showing previous comparisons of global temperatures change from observations and climate models were comparing slightly different things, causing them to appear to disagree far more than they actually do.

The lead author Kevin Cowtan has a backgrounder on the paper here and data and code posted here. Coauthor /u/ed_hawkins also did a background post on his blog here.

Basically, the observational temperature record consists of land surface measurements which are taken at 2m off the ground, and sea surface temperature measurements which are taken from, well, the surface waters of the sea. However, most climate model data used in comparisons to observations samples the air temperature at 2m over land and ocean. The actual sea surface temperature warms at a slightly lower rate than the air above it in climate models, so this apples to oranges comaprison makes it look like the models are running too hot compared to observations than they actually are. This gets further complicated when dealing with the way the temperature at the sea ice-ocean boundaries are treated, as these change over time. All of this is detailed in greater length in Kevin's backgrounder and of course in the paper itself.

The upshot of our paper is that climate models and observations are in better agreement than some recent comparisons have made it seem, and we are basically warming inline with model expectations when we also consider differences in the modeled and realized forcings and internal climate variability (e.g. Schmidt et al. 2014).


https://www.reddit.com/r/science/comments/3flzb4/science_ama_series_climate_models_are_more/