Boy, first time I heard that argument. Imagine, sun spots are caused by fossil fuel burning on the third rock from the sun.

Astounding, how those greenhouse gases from the tailpipe of my SUV travel across ninety three million miles of vacuum and affect the hydrogen fusion reactions of the sun!

Actually, I heard a talk on this at Harvard in 1992, and the reporter has it a little garbled. The non-thermal radiation from the sun varies, with a strong cyclical component with a roughly 250-year period. We had the last minimum in about 1890 and are approaching the next maximum. The variation comes from large-scale magnetic fluctations which also affect sunspots and determine in particular the length of the sunspot cycle (which also varies around 11 years).

This non-thermal radiation is mainly absorbed in the upper atmosphere. While it can dramatically raise the temperature of the upper atmosphere, its total energy is not enough to warm the earth's surface by a full degree if the energy gets thermally distributed. However, because the energy is absorbed locally and pushes the atmosphere out of equilibrium, there may be some nonlinear amplification process going on. Otherwise, the variation in solar emissions needs to be accompanied by some other warming mechanism.

If they can show that the variation in Earth surface temperatures tracks the solar cycle over many centuries, that suggests that there is a nonlinear amplification process and this may be the source of natural temperature variations. If so, then the Earth's surface temperatures will probably peak sometime before 2025 and then start cooling.

I read an interview with an English astronomer about this a few years ago. It was funny how he bent over backward to avoid offending the 'greenies.' No doubt he was afraid his observatory would be vandalized.