We recently presented and discussed modeled and observed global surface temperatures in absolute terms. See the post On the Elusive Absolute Global Mean Surface Temperature – A Model-Data Comparison. The WattsUpWithThat cross post is here. Yesterday, Willis Eschenbach at WUWT furnished EXCEL spreadsheets that included the outputs of climate model simulations of global surface temperatures in absolute terms. See Willis’s post CMIP5 Model Temperature Results in Excel.
Hot on the heels of those two posts comes a discussion at RealClimate of modeled absolute global surface temperatures, authored by Gavin Schmidt, the head of the Goddard Institute of Space Studies (GISS). Gavin’s post is Absolute temperatures and relative anomalies. Please read it in its entirety. I believe you’ll find it interesting. (Thanks, Gavin.)
Here are two quotes from it to get the discussion here rolling. First, Gavin Schmidt wrote (my boldface):
Second, the absolute value of the global mean temperature in a free-running coupled climate model is an emergent property of the simulation. It therefore has a spread of values across the multi-model ensemble. Showing the models’ anomalies then makes the coherence of the transient responses clearer. However, the variations in the averages of the model GMT values are quite wide, and indeed, are larger than the changes seen over the last century, and so whether this matters needs to be assessed.
Second quote (my boldface):
Most scientific discussions implicitly assume that these differences aren’t important i.e. the changes in temperature are robust to errors in the base GMT value, which is true, and perhaps more importantly, are focussed on the change of temperature anyway, since that is what impacts will be tied to. To be clear, no particular absolute global temperature provides a risk to society, it is the change in temperature compared to what we’ve been used to that matters.
See, I told you you’d find Gavin’s post interesting.
Enjoy your holidays.