Corroboration – Again
Posted by Jeff Id on September 11, 2011
It looks like the “skeptics” (if that’s what you call them) were right again. Steve McIntyre pointed out a paper in print at GRL that was similar in content to some of his an Ross McKitrick’s own work (MMH10)demonstrating again that climate models run generally higher than observations. This is particularly true in the case of the tropical warming in the upper troposphere covered in this paper - On the warming in the tropical upper troposphere:Models versus observations (free). The paper was written by Qiang Fu, Syukuro Manabe, and Celeste M. Johanson (FMJ11).
 IPCC (Intergovernmental Panel on Climate Change) AR4 (Fourth Assessment Report) GCMs (General Circulation Models) predict a tropical tropospheric warming that increases with height, reaches its maximum at ∼200 hPa, and decreases to zero near the tropical tropopause. This study examines the GCM‐predicted maximum warming in the tropical upper troposphere using satellite MSU (microwave sounding unit)‐derived deeplayer temperatures in the tropical upper‐ and lower‐middle troposphere for 1979–2010. While satellite MSU/AMSU observations generally support GCM results with tropical deep‐layer tropospheric warming faster than surface, it is evident that the AR4 GCMs exaggerate the increase in static stability between tropical middle and upper troposphere during the last three decades. Citation: Fu, Q., S. Manabe, and C. M. Johanson (2011), On the warming in the tropical upper troposphere:
My bold of course. This is a key factor in the global warming debate as the missing hot spot is an indicator that feedback mechanisms are not properly quantified in climate models. The results of FMJ11 are rather stunning to see in print these days as there was um …. considerable review difficulty experienced in rebutting the Santer 08 paper claiming that models do match observations. It is worth noting that Santer has a new paper out on the topic which I will discuss in another post here.
Now this is a slightly different claim than Santer and MMH10 which looked at simple trends of the atmosphere, but the result is perhaps more important in that climate science is now recognizing in print that key differences between observed vs modeled feedbacks DO exist and that modeled trends are overstated. I have yet to see any of the best known climate scientists admit these unquestionable discrepancies. The methods of the paper seem reasonable enough and are not difficult to follow except that you do need to understand the data in question is the difference in the temperature trends between tropical upper‐ and lower‐middle troposphere (T24‐T2LT) as defined and discussed in the paper linked above. How much upper vs lower troposphere warming is observed is a result of CO2 heat capture and feedback in real world and modeled climate systems.
Below is the key plot of modeled vs observed temperatures:
As we have seen so often in blogs and print, the models run hot in comparison to observed trends both individually and in aggregate. Again, the difference here is that this paper analyzes the heat buildup region of the tropical troposphere which is a key prediction of climate models. This is different from the result of MMH10 which shows that the model trends are generally high. Instead, this is a clue to the reason as to WHY they are running high.
In the text, however, a simple statement is made which corroborates MMH10, the numerous posts by Chad Herman at TreesFortheForest and Steve McIntyre on Briffa 08, Lucia and others and contradicts the general conclusions of Santer08 that climate models are accurately representing observation.
Tropical surface temperature trend from multi‐model ensemble mean is more than 60% larger than those from observations (Table 1), indicating that AR4 GCMs overestimate the warming in the tropics for 1979–2010. Thus larger T24‐T2LT trends from AR4 GCMs are partly caused by GCM overestimation of tropical temperature trends.
The models are running too hot. Either that or the thermometers need to be replaced. There has been a lot of denial in the climate scientist community on these basic facts perhaps we should begin collecting quotes for the future retractions as the main stream will soon need to address this reality. One can’t help but wonder if a change in predicted warming magnitude will affect the overall anti-industrial, anti-capitalist message of the climate community.
The conclusion with my bold:
One of the striking features in GCM‐predicted climate change due to the increase of greenhouse gases is the much enhanced warming in the tropical upper troposphere. Here we examine this feature by using satellite MSU/AMSUderived deep‐layer temperatures in the tropical upper‐ (T24) and lower‐ (T2LT) middle troposphere for 1979–2010. It is shown that T24‐T2LT trends from both RSS and UAH are significantly smaller than those from AR4 GCMs. This indicates possible common errors among GCMs although we cannot exclude the possibility that the discrepancy between models and observations is partly caused by biases in satellite data.
IPCC AR4 GCMs overestimate the warming in the tropics for 1979–2010, which is partly responsible for the larger T24‐T2LT trends in GCMs. It is found that the discrepancy between model and observations is also caused by the trend ratio of T24 to T2LT, which is ∼1.2 from models but ∼1.1 from observations. While strong observational evidence indicates that tropical deep‐layer troposphere warms faster than surface, this study suggests that the AR4 GCMs may exaggerate the increase in static stability between tropical middle and upper troposphere in the last three decades. In view of the importance of the enhanced tropical upper tropospheric warming to the climate sensitivity and to the change of atmospheric circulations, it is critically important to understand the causes responsible for the discrepancy between the models and observations.
With so many papers coming out in support of a less severe warming effect, the climate community might do well to accelerate the release of AR5 before they are forced to recognize these problems. As an aside, it isn’t the message that is causing public opinion to change, it isn’t the fact that the public doesn’t understand, it is the regular discovery of the truly uncertain nature of the climate future which cuts into the message.