I noticed a discussion on Twitter about whether or not, from basic physics, we know that most of the warming since the 1800s has been anthropogenic. Of course, it’s probably not basic physics, because it is quite complicated. However, I do think – given our current understanding – that we can use some basic physics to show just how difficult it is to construct a plausible scenario under which most of our warming was not anthropogenic. I had thought of writing a post, but realised I had already largely done so, so am reblogging the one below. Admittedly, I wrote this one with respect to 1950, but a similar argument could be made based on warming since the 1800s.
Essentially, given how much we’ve warmed (~ 1K), given the estimates for the external changes (solar, volcanoes, anthropogenic, …), and given that we still have a planetary energy imbalance (we’re still accuring energy) it is very difficult to construct a physically plausible scenario under which most of the warming is not anthropogenic. Of course, this isn’t some kind of claim of formal attribution, just a back-of-the-envelope approach to illustrate the point. It may also be possible to construct an alternative that is both physically plausible, and not inconsistent, but I can’t think of how. If anyone can, feel free to point out how in the comments. Of course, I’m looking for more than just hand-waving.
The latest critique of consensus studies is an attempt to re-analyse the data from Verheggen et al. (2014) to suggest that the consensus amongst climate scientists is only 47%, not 97%. I only have two things to say about this. Firstly, As Michael Tobis points out, you do need to consider who you include as a scientist, what question you are asking, and how you go about asking it. Secondly, these consensus studies are not to inform those who work in – or understand – this scientific area; it’s for those who do not and for those who dispute the existence of a strong consensus. If you analyse survey data that aims to address this issue and conclude that the level of consensus with respect to AGW is less than 50%, then you’re wrong. It’s clear (whether you look in the scientific literature or speak to relevant…
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