During the last week, there have been three cosmoclimatological preprints by two teams on the arXiv. Rusov et al. (Ukraine) argue that all observed climate change at the timescale of millenia and millions of years can be explained by two factors, namely the the solar output and the galactic cosmic ray flux that determines the cloudiness.Twomey effect. In the second paper, their bifurcation model is compared with the EPICA data.
On the other hand, Terry Sloan (Lancaster) and A.W. Wolfendale (Durham) show that in some places, the cloud cover is anticorrelated with the cosmic ray flux relatively to what is expected. At the 95% confidence level, they claim that less than 23% of the changes of the cloudiness during the 11-year cycles is caused by cosmic rays.
A very convincing criticism of the paper by Sloan and Wolfendale was written by Nir Shaviv in April 2008.
Hat tip: Physics arXiv blog