A few days ago I linked to the new Verheggen (John Cook) et al paper, a survey of opinion among climate scientists. A tweet today reminded me of something I had noticed in skimming through the paper which is rather interesting. It concerns climate scientists' views on feedbacks, forcings and climate sensitivity.
At first glance the survey results on ECS are unremarkable, with the modal position being right in the middle of the official IPCC range, centred on 3°C. However, recall that if GCM output is to correctly hindcast the observations, there is a balance to be struck between climate sensitivity and aerosols: to the extent that sensitivity to carbon dioxide is high and therefore warming is large, you have to have a big cooling effect from aerosols in the twentieth century to prevent the GCM hindcast of warming outpacing what happened in the real world.
Now take a look at climate scientists' views on forcings, and in particular the aerosol forcing. The survey results are split into the opinions of those who think carbon dioxide is responsible for more than half of recent warming and those who think it's responsible for less than half. Let's call these the big warmers and the lukewarmers. Slightly confusingly the relevant graph shows the lukewarmers in red and the big warmers in blue. Here is is an extract, showing the results for aerosols (click for larger):
;)
If I understand the caption correctly, roughly 19% of lukewarmers offered an opinion on why they think we are not going to fry, at least as regards aerosols. And as you can see, most of those who answered this followup question suggest, with impeccable logic, that the influence of aerosols is slight - the pale red section is long, and much longer than the tiny dark red section. However, the big warmers seem equally inclined to think that the aerosol influence is weak as they do strong. Moreover, very few big warmers seemed inclined to discuss aerosols at all.
How can this be? Don't they understand how central a strong aerosol effect is to their case?
(Caveat: the paper is hard to follow, so it's possible I'm misunderstanding something. It seems to hint at some inconsistencies with scientists' views on aerosols.)