CERN's CLOUD experiment that uses a particle-physics-based device to study the effects underlying the cloud formation just published a new paper in Nature and a corresponding press release:
Molecular understanding of sulfuric acid–amine particle nucleation in the atmosphere (Nature, by Almeida and dozens of co-authors)I don't want to copy all the information you may find above so let me be brief.
CERN’s CLOUD experiment shines new light on climate change (CERN press office)
For a while, it's been more or less known that the sulfuric acid \(H_2 SO_4\) itself (I mean using the U.S. spelling with an "f") isn't enough to produce the cloud condensation nuclei. Is there another compound that helps?
They studied what happens in their chamber if they add realistic concentrations of an amine, namely dimethylamine. And they found out that the formation rate is extremely sensitive to the concentration of this stinky odor.
Their even claim that their observations may be reproduced by a quantum mechanical calculation. This would suggest a rather advanced degree of understanding of what's going on.
For this particular combination of compounds, the folks seem to experimentally deduce that the presence of cosmic rays has a negligible (but probably measurable by them) impact on the formation rate. However, they point out that it doesn't exclude the possibility that different combinations of compounds may also contribute to the formation of clouds and they could be sensitive to the cosmic ray flux.
Note that amines are compounds with a single nitrogen atom \(N\) at the center that may be considered derivatives of ammonia \(NH_3\). All of those things smell sort of similarly to the ammonia.
Dimethylamine that was used and demonstrated to matter is \((CH_3)_2 NH\) which means that two of the three ammonia's hydrogen atom branches are replaced by two copies of the methyl group, \(CH_3\), which still has one free 'hand" to be connected to the nitrogen atom. Incidentally, trimethylamine is similarly \((CH_3)_3 N\) – all the branches are replaced by the methyl group – and this amine is the primary component in the odor of rotten fish (and the typical bad breath or bacteria-based vaginal odors) in the real world.
Apologies for this repulsive appendix. TRF readers who are members of the IPCC might conclude that while men cause global warming, women cause global cooling. ;-)
If they're right, then I would think that it's about equally likely as not that the amine-sulfuric-acid combination is representative and cosmic rays are unimportant for cloud formation in general. However, there may be vast enhancements for other molecules and/or other indirect processes that make the cosmic rays matter. The Shaviv-Veizer geological correlation remains the most important reason why your humble correspondent tends to believe that the cosmic ray flux cannot be negligible.
At any rate, they surely show that the cloud formation does depend on many chemical properties of the atmosphere. One could say that they have pretty much shown that bad breath and rotten fish cause global cooling.