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.
Bob Tisdale - Climate Observations 
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Thanks, Bob. Very interesting Schmidt talk.
I found Aaron Lewis comment very interesting too:
“Ok, the models have done a pretty good job of estimating global temperature anomalies. And, it is nice to be able to give the modelers kudos for a win. (We were not so sure, running card decks in the basement of NCAR in 1964.) However, are GLOBAL temperature anomalies useful in the real world? Did they warn us of the 2007 Arctic sea ice retreat? Did it warn us of the ongoing Antarctic glacier (PIG) bottom melt? All of the real impacts and effects of AGW are local events – weather as it were. People have died in heat waves affected by AGW. However, those people died from the local temperature, and not the average global temperature.”
All climate, weather, is local in its effects. This I’m learning from Jim Steele (Landscapes & Cycles. 2013).
Steele attacks papers on local populations that base their findings on global temperatures and shows how the local temperatures for those studies had in fact been dropping.
Be happy!
Actually, what Schmidt calls observations are emergent properties of the models used to create them initialized with temperature data. 8>)
Merry Christmas!
Reblogged this on Centinel2012 and commented:
What I get from this is that there is neither the accuracy nor the precision in the output of the models; so they homogenize the real world data into making the anomalies match the simulations. They disguise the meaningless of there system with fancy words to try and make it seem that they really know what they are doing.
The problem they have is Mother nature doesn’t give a hoot about the system, GCM’s theories and fancy words so they are left with models that say its supposed to be getting hotter and the real world that is not. The only good that can possibly come of this travesty is that sometime in the near future we will decouple science and engineering from politics!
Sorry for the rant but I’m of the generation that went to the moon and back using slide rules!
Gavin Schmidt has jumped the shark with this one.
Baselines, trends and absolutes are the foundation of the AGW argument. It means … Accumulating (integrating) a constant process (derviative), upward with time as it disburses through space.
If the trend is wrong, it means that the differential is unsuitable, that the foundation of the model is seriously flawed. The benefit of sticking to a baseline and integrating forwards in time is that fluctuations will cancel out and the differential will ‘prove’ (demonstrate) itself to be true (reasonably appropriate) in the long run.
Now we are being ask to refocus on anomolies. We are told thst it is the change from what we are familiar and expect is thst which is importsnt in all this. … Yes exactly. The uncertainty monster is a very different type of beast.
People change, animals change, ecosystems change as a result of anomolyous events. New rules come into effect. There are new attitudes. The relevant differentials changes
Schmidt’s essay is written very poorly. For instance:
“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.”
To what does the word “this” refer?
Reblogged this on Globalcooler's Weblog and commented:
Ever wonder why everyone produces anomalies instead of absolute temperatures? You’ll have to read the references to get the whole story. Worth the effort.
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