I have come across four scientific papers published recently, all of which support the climate realist perspective, and thought them of such significance that I should share them here, in my climate realist paper update series.
The CLOUD experiment at CERN has come out with four new, important papers (though the fourth wasn’t officially published by CLOUD, it had many authors from it), three of which were published in Nature journals. I will go over each of them and their importance for the cosmic-ray climate connection here. (I also thought this would be a good time to write a post like this seeing as I’m starting on the list of significant papers on the cosmic-ray climate connection.)
The first paper, The role of low-volatility organic compounds in initial particle growth in the atmosphere (a press release covers papers one, two, and four here), has been published in Nature. It examines how organic particle formation takes place and the role of particle volatility in it. Its implications are that oxidized organic particles formed by cosmic rays (see second paper) can grow large enough to serve as cloud seeds.
The second paper, Ion-induced nucleation of pure biogenic particles, has also been published in Nature. It finds that ions produced by galactic cosmic rays can significantly influence the formation rate of the oxidized particles talked about above, from 1 to 2 orders of magnitude, and that because of this, in unpolluted areas, cosmic rays may play a large role in cloud formation, because the particle clusters that have been stabilized by cosmic rays can grow large enough to serve as cloud seeds (see the first paper). In addition, aerosol particles produced by cosmic rays make clouds brighter and more long-lived, cooling the earth even more. This is highly important (and favorable) for Henrik Svensmark’s theory about cosmic rays, clouds, and climate, as well as for climate sensitivity and future climate projections. However, because cosmic rays affect sulfuric acid-driven particle growth less than biogenic particle-driven growth and we’ve been emitting it into the atmosphere, cosmic rays have less of an effect now than they used to. As well as this, it means that the pre-industrial atmosphere may’ve been cloudier than previously believed, and that because of this, climate sensitivity and projections should be revised slightly downward. This is because climate models assume humans have offset quite a bit of warming by forming clouds through emission of sulfuric acid, which is though to be the main gas responsible for aerosol particle formation. However, if there were more clouds in the pre-industrial atmosphere then we have formed less clouds and offset less warming than scientists have thought.
The third paper, The effect of acid–base clustering and ions on the growth of atmospheric nano-particles (press release which covers it and the second paper here), has been published in Nature Communications. It finds that increasing ions (as well as other things) will increase nanoparticle growth rates where sulfuric acid (as opposed to biogenic particles from trees) is driving particle formation. This may lead to those particles becoming larger and forming more cloud seeds and thus clouds. This lends even more support to Svensmark’s theory. A press release covers this paper as well as the second paper.
The fourth paper, New particle formation in the free troposphere: A question of chemistry and timing, has been published in Science. It essentially confirms that the findings of the first two papers are taking place in the real atmosphere, not just a cloud chamber. While this paper too is supportive of Svensmark’s theory, it also adds that:
Neutral nucleation is more than 10 times faster than ion-induced nucleation
So, in conclusion, cosmic rays significantly influence a possible mode of cloud formation that dominated in the past, and the pre-industrial climate may have been cloudier than previously thought, so climate sensitivity and projections of future climate change may need to be adjusted to be lower (though these last two are only implied in the papers). Interestingly, the English-language media has not reported very widely on the cosmic ray aspect of these papers (and the third was hardly talked about at all), though I think they are very important in regards to the Svensmark hypothesis and that the public should know this.
Furthermore, these results and my conclusions from them bolster and are bolstered by previous results of the CLOUD experiment, see Duplissy et al. 2010 and Kirkby et al. 2011. In my opinion, already the CLOUD experiment has essentially confirmed the Svensmark hypothesis: that there is a significant effect of galactic cosmic rays on clouds and climate.