There’s an interesting new paper by Smith et al. called Role of volcanic and anthropogenic aerosols in the recent global surface warming slowdown. A few months ago, I went to a seminar where one of the authors discussed this paper. I didn’t write about it at the time as there wasn’t a paper yet, but now that it’s out, I can do so.
There’s not really all that much to say, since Carbon Brief has covered it in some detail. The basic idea is that the supposed slowdown in surface warming is largely driven by a negative phase of the Pacific Decadal Oscillation (PDO), and partly by a recovery from Pinatubo. However, as illustrated in the figure below, at least some of the negative phase of the PDO is forced by aerosol emissions, mainly from China. Therefore, at least part of the supposed surface warming slowdown is externally forced.
Maybe the key consequence of the results in this paper is
The external factors that contributed to the GMST slowdown therefore appear to be diminishing or reversing. Barring a major volcanic eruption, and assuming continued aerosol mitigation especially in China, this suggests that GMST trends may increase rapidly over the coming few years.
Certainly seems true so far. We’ll have to wait and see if it continues. If we continue to increase our CO2 emissions, while also reducing aerosol emissions, it certainly won’t be all that surprising.