Suricat, here's hot from the press an excellent presentation by Richard Lindzen which indicates extremely strong empirical evidence that climate sensitivity is very low approx 0.5 deg C.
The only conclusion that I can draw from it is that there is a strong negative feedback mechanism that responds to anthropic warming.
Whether it's Lindzen's iris effect or increased organic material in the atmosphere increasing cloud cover doesn't matter as the effect of the phenomenon has been clearly measured. I think the piece of work by Lindzen will go down in the annals as a real tipping point in the AGW debate.