Essentially the argument is that we know what we need to know from the GCMs, and should stop modelling and start mitigating. Tom's reply is that, despite what the denialists would have you believe, the actual expense of GCMs to date is trivial.
Actually, they could get massively better with an order of magnitude more spending and an importation and empowerment of real software management talent. I once tried to interest Google in taking this on. They stopped returning my calls, alas.
Vranes' argument is that this counts for nothing. The government shouldn't do it and Google shouldn't do it. Nobody should pay anything for GCMs, because the purpose of GCMs is to tell us we're in trouble, and they have already done their job.
Vranes is wrong. That is not, as some argue, because the GCMs are insufficient to tell us we're in trouble. Hell, we don't even need the GCMs to know we're in deep. As realclimate said a while back:
The main reason for concern about anthropogenic climate change is not that we can already see it (although we can). The main reason is twofold.Vranes is wrong because it's time to get down to brass tacks on the adaptation side. It's time to start computing in earnest to support the adaptation question, which is pretty much what the Ramanthan NAS panel is saying.
(1) Carbon dioxide and other greenhouse gases are increasing rapidly in the atmosphere due to human activity. This is a measured fact not even disputed by staunch “climate skeptics”.
(2) Any increase in carbon dioxide and other greenhouse gases will change the radiation balance of the Earth and increase surface temperatures. This is basic and undisputed physics that has been known for over a hundred years.
Eli sensibly argues that adaptation without mitigation is insane. This is true. On the other hand, it's far too late to have a pure mitigation strategy. The main applied science role of the large climate models should be to inform adaptation.