[qam1]

The galactic (not solar) cosmic rays that hit the earth may cause warming. The sun's role is that its weakining magnetic field may let more cosmic rays in. The same effect would not occur on Mars because there are no clouds to be enhanced by the cosmic rays.

You are wrong, There are water vapor clouds on Mars

And yes like on Earth these clouds drive weather on Mars

See MARS'CHAOTIC CLIMATE

Mars' climatic interactions between dust and water ice clouds: The dusty perihelion climate was observed by Viking and Mariner 9 and by NRAO in 1992,1994, and 1996. What the 1970's orbiters did not identify was the very distinctive climate of Mars at aphelion--the farthest point in its orbit to the Sun--, with its planet-wide belts of water ice clouds. It is the cold atmospheric conditions of Mars during aphelion, when the Sun's effect is much weaker, that stimulate the formation of these water ice clouds. The clouds reduce atmospheric temperatures by forming around the dust acting as condensation nuclei,reflecting sunlight back out into space and once frozen the dust falls to the ground. This competition between dust heating in the summer and cloud cooling in the winter drives the sweeping annual and short-term regional changes in Mars' climate.

Less Cosmic rays = less cloud formation on Mars = Less Cooling = more warming.

Explains the huge dust storms in 2001, 2003 and 2005

[palmer]

Yes, I didn't realize there was so much weather on Mars, and the same sulfur and water vapor are there to produce the same condensation effect (or lack thereof) from cosmic rays. Maybe theguys who ran the lab experiment of earth's atmosphere can do the same with Mars.