Hansen again. He seems to have got bored with saying climate sensitivity is 6 oC, and now agrees with JA that its 3 oC. Hurrah. Less excitingly, his estimate for all-ice-sheet melt on 2-3 x CO2 is now “it would take some time”, which has the virtue of vagueness.
But far more excitingly, he is now pushing the idea that Earth could be heading towards a Venus type runaway greenhouse effect, apparently with added forcing as small as 10-20 W/m2. (over present day or over pre-industrial? What CO2 level would that be? Not sure, but In my opinion, if we burn all the coal, there is a good chance that we will initiate the runaway greenhouse effect. If we also burn the tar sands and tar shale (a.k.a. oil shale), I think it is a dead certainty. Perhaps we are expected to guess what Hansens estimate of total coal reserves is). Sadly he seems to have omitted the reference to the paper where the fine details have been published, but I’m sure that just a matter of time. I’m sure I can leave the likes of JA and RMG to rip the fine details to shreds.
As an encore, he has yet another go at defining tipping points. There are where Climate forcing (greenhouse gas amount) reaches a point such that no additional forcing is required for large climate change and impacts. Try to play that around D-O events (removing the unreasable restriction that forcing has to be from GHG amount).
There are some tantalising headlines about intergenerational equity, but no substance.