Like many I've found that Anthropogenic caused global warming to be a bit too easy, and the leap from contributing factor to causality to be across a chasm a bit too wide. Researcher Henrik Svensmark's* work on cosmic rays seeding low cloud formation seems to suggest the the influence of the solar magnetosphere in shielding the Earth from cosmic rays and the clouds they form is 1.2 watts per square meter compared to the 1.4 watts per square meter attributed to man-made CO2.
The Danish scientists put together several well-established scientific phenomena to arrive at their novel 1996 theory. The sun's magnetic field deflects some of the cosmic rays that penetrate the Earth's atmosphere, and in so doing it also limits the immense amounts of ions and free electrons that the cosmic rays produce. But something had changed in the 20th century: The sun's magnetic field more than doubled in strength, deflecting an extraordinary number of rays. Could the diminution of cosmic rays this century have limited the formation of clouds, making the Earth warmer? reported Lawrence Solomon, in The sun moves climate change
interestingly this would mean that those who are proposing seeding sulfur oxides in the atmosphere to generate clouds would be merely replacing what the solar magnetosphere is blocking.
*Henrik Svensmark is director of the Centre for Sun-Climate Research at the Danish Space Research Institute (DSRI). Previously, Dr. Svensmark was head of the sunclimate group at DSRI. He has held post doctoral positions in physics at University California Berkeley, Nordic Institute of Theoretical Physics, and the Niels Bohr Institute. In 1997, Dr Svensmark received the Knud Hojgaard Anniversary Research Prize and in 2001 the Energy-E2 Research Prize.