Nigel Calder has pointed out the following interview in Physics World about CERN's CLOUD experiment:
In that interview, CLOUD's boss Jasper Kirkby answers lots questions - like what are the cosmic rays and whether the climate scientists in the world agree that someone should be allowed to believe, as a heretic, that the clouds may affect the weather. ;-)
Kirkby is giving lots of relevant answers and he also credits Nigel Calder himself for some early motivation to build the experiment more than a decade ago.
The main punch line is that the experiment has found that the cosmic rays substantially increase the production of the aerosol seeds of clouds. They have also measured the detailed evolution of the size of those particles and within 2 or 3 months, we will see some published results.
See older TRF stories on cosmoclimatology.