A month ago, before Eli and Ms Rabett fell into deep depression, an interesting and important paper appeared in Science. While the conclusions are in the paper, the exhaustive supplementary material is where the at is at.
The paper "Global atmospheric particle formation from CERN CLOUD measurements" covers a huge range of experiments done in the CERN CLOUD chamber to try and tease out the source of atmospheric particle formation (that is the title), and the conclusion is about what any rational bunny who has been following the CERN experiments and other work and work from long ago would have expected,
Fundamental questions remain about the origin of newly formed atmospheric aerosol particles because data from laboratory measurements have been insufficient to build global models. In contrast, gas-phase chemistry models have been based on laboratory kinetics measurements for decades. Here we build a global model of aerosol formation using extensive laboratory-measured nucleation rates involving sulfuric acid, ammonia, ions and organic compounds. The simulations and a comparison with atmospheric observations show that nearly all nucleation throughout the present-day atmosphere involves ammonia or biogenic organic compounds in addition to sulfuric acid. A significant fraction of nucleation involves ions, but the relatively weak dependence on ion concentrations indicates that for the processes studied variations in cosmic ray intensity do not significantly affect climate via nucleation in the present-day atmosphere.
In other words, the conclusion from well before the evil danes stirred up the denialists with their cosmic ray fantasy holds. Cosmic rays do not play a significant, if any role in formation of the aerosols, there are always enough of them around that they are not limiting and the slight increase from cosmic rays plays no role.
What this paper and the supplementary material do is to assemble a large and complete set of laboratory data from which a kinetic model can be built and compared both with experiment and observation. That is science.
The interesting part, which this work reinforces, but to Eli was first pointed out by a bunch of Finns who instrumented the North Woods, and who are part of the team publishing the current work, is that amines, particularly ammonia turn out to be the limiting factor in the atmosphere for formation of particulates which grow into clouds. The lab data clearly show the enhancing effect of adding ammonia or amines in small concentration to the chamber, but more interesting perhaps is the model prediction for the effect of the solar cycle (aka cosmic rays) and the increase of ammonia concentration since preindustrial times.