What do we know about climate changes?

The only current "evidence" for blaming carbon emissions [for global warming] are scientific models (and the fact that there are few contradictory observations). Historically, science has not progressed by calculations and models, but by repeatable observations. Some theories held by science authorities have turned out to be spectacularly wrong: heavier-than-air flight is impossible, the sun orbits the earth, etc. For excellent reasons, we have much more confidence in observations by several independent parties than in models produced by a small set of related parties!

I Was On the Global Warming Gravy Train, by David Evans.