An interesting blog by Andrew Revkin discussing activist James Hansen’s latest
Armageddon postponed direst ever warning/press release to stoke the fires of alarm ahead of Paris- because there may have been a slight gap in the wall-to-wall coverage the mainstream has missed. Of particular note is Kevin Trenberth’s comments on how much the computer models fail to model reality (my bold).
No mention is made of ENSO or Pacific decadal variations that dominate interannual and decadal variability in the real world, and which are a key to understanding the recent hiatus, and recent trends that are not representative of longer-term trends, although frequently interpreted as such. In section 4.5, the authors point out the need to simulate a number of features realistically and the model does not really do them very well, especially basic things like sea surface salinity. So the relevance of the model is not established. They use the model for a number of highly artificial experiments that are supposed to depict melting of ice at high latitudes: ”freshwater injection.” These experiments introduce a lot of very cold fresh water in various places, and then they see what happens. The question is how relevant these are to the real world and what is happening as global warming progresses? They do not seem at all realistic to me.
A key to a lot of this is how clouds change, and one needs to get clouds right in the first place to have confidence in the results. Unfortunately, this is an area where major problems exist. Huge problems occur over the southern oceans for instance and ***all models have far too much sunshine penetrating to the surface compared with observations***. No doubt the southern ocean, featured strongly by Hansen et al, plays an important role, but data there are poor, and change is not well known; in particular the recent hiatus in global warming greatly influences any observations, which can therefore be quite misleading wrt trends. I certainly do not believe the result claimed with regard to less snow over Antarctica with a warming climate. Although Hansen argues that the real world is responding even faster than in the model scenarios, this is not at all clear owing to the natural variability.