I’d have to agree with Peter Lang that it is “extremely unlikely” that IPCC will waver from its “CAGW” message, no matter what the latest science shows.
The dilemma for IPCC, however, is that “the cat is out of the bag”.
As Judith stated earlier, it will be difficult for IPCC to brush the new data “under the rug” and retain any semblance of credibility.
But it would be even more painful to admit that past reports exaggerated certainty when it came to the impacts of AGW – and, worse yet, that they also exaggerated the magnitude these impacts.
The most damaging news for IPCC were the two recent studies based on physical observations (Lewis and Schlesinger), which indicate that (2xCO2) equilibrium climate sensitivity (the alpha and omega of the “CAGW” premise) is very likely to be around half of the values previously predicted by the climate models.
These followed earlier studies based on CERES and ERBE satellite observations (Spencer + Braswell 2007, Lindzen + Choi 2009/2011), which also showed low climate sensitivity.
Let’s see how IPCC handles this new situation in its AR5 report.
My guess is that IPCC (in keeping with its past tradition) will try to “tough it out” as long as this is possible, maybe with some quick rebuttals to the damaging reports, but that this policy will eventually backfire, as it loses all the credibility it still had left after Climategate, etc.
However, I expect that the days for IPCC’s “CAGW” position are numbered scientifically, even though the politically-driven multi-billion dollar big business that “CAGW” has become may continue to lumber on a bit longer before it finally collapses under its own weight.
2013 should be an interesting year.
Max