No Link Between Cosmic Rays and Global Warming

According to Sloan and Wolfendale, the 2000 paper highlighting the connection between cosmic rays and low-level clouds completely avoids clouds at other altitudes. This is surprising because cosmic ray ionization should increase with altitude. Cosmic rays should be intercepted earlier by the atmosphere and turned into clouds, not down at the lowest altitudes. If cosmic rays were to blame, you would expect the exact opposite, with more high-altitude clouds.

It can't be ruled out, but it's pretty unlikely.

Abstract: It has been claimed by others that observed temporal correlations of terrestrial cloud cover with ‘the cosmic ray intensity’ are causal. The possibility arises, therefore, of a connection between cosmic rays and Global Warming. If true, the implications would be very great.
We have examined this claim to look for evidence to corroborate it. So far we have not found any and so our tentative conclusions are to doubt it. Such correlations as appear are more likely to be due to the small variations in solar irradiance, which, of course, correlate with cosmic rays. We estimate that less than 15% of the 11-year cycle warming variations are due to cosmic rays and less than 2% of the warming over the last 35 years is due to this cause. (8 page PDF)

From Wired
HT: Is It Getting Warmer