Roger Pielke Sr. comments on Michael Mann: "significant positive radiative feedback from added water vapor" or lack thereof

Roger Pielke Sr. dissects a Michael Mann interview:

“The details, how much warming you get, depend on things like feedbacks. And you can’t incorporate feedbacks through a back of the envelope approach. You actually have to critically think about the interactions that take place in this very complex system. And those feedbacks ultimately determine the extent to which that initial warming will be amplified, but they don’t even change the fact that you elevate greenhouse gas concentrations in the atmosphere and you’ll get a warming of the surface. That’s basic physics and chemistry and people who claim that they don’t believe that, they don’t believe we’re warming the planet through increasing CO2 levels because of climate models, they don’t understand the fact that you don’t need a climate model to come to that conclusion. It’s basic physics and chemistry.

My Comment: Mike is arguing about an issue that is not in disagreement! Of course, if you add greenhouse gases, there is a radiative warming effect. However, its magnitude is relatively small unless there is a significant positive radiative feedback from added water vapor. It is this feedback, which involves the entire hydrologic cycle that is still so poorly understood; e.g. see

Stephens, G. L., T. L’Ecuyer, R. Forbes, A. Gettlemen, J.‐C. Golaz, A. Bodas‐Salcedo, K. Suzuki, P. Gabriel, and J. Haynes (2010), Dreary state of precipitation in global models, J. Geophys. Res., 115, D24211, doi:10.1029/2010JD014532.