Well, we knew that anyway, but there is some more stuff out on it, says the BBC: The Svensmark hypothesis is that when the solar wind is weak, more cosmic rays penetrate to Earth. That creates more charged particles in the atmosphere, which in turn induces more clouds to form, cooling the climate.
The solar folk tend to take this on a long term basis, which is fraught with problems because the cloud obs aren’t good over those scales due to inter-satellite calibration etc etc. But Sloan et al. seem to have decided to take Svensmark seriously (which most people don’t :-) and look to see if short-term cloud changes correlate to short-term changes in cosmic rays (because the mechanism, if it works at all, should also work on short time scales). The result: they don’t, and hence it doesn’t.
You can, if you please, discuss this theory over at The Sun but as you’d expect the level of discussion is rather low: apparently it was much warmer 25 kyr ago and much colder 100 kyr ago. Ah well -W]