Quote:
I don't think that there is irrefutable evidence of global warming.


There is no such thing as "irrefutable evidence" in science.

Quote:
I have to think that the sun's radiation levels vary and change over time, and that has a greater shorter term impact than man-made pollution.


Actually, stellar thermodynamics are probably the most well-understand part of this whole debate. What the sun is doing, long-term, is very very predictable. We have about 100 million years to either get off the planet or get the orbiting solar panels in place. I'm guessing it will be the latter, with about 99.5 million years to spare.