Re: Re: Re: Re: This just leaves one small question.
Here are two statements that are completely agreed on by the IPCC. It is crucial to be aware of their implications:
1. A doubling of CO2, by itself, contributes only about 1C to greenhouse warming. All models project more warming, because, within models, there are positive feedbacks from water vapor and clouds, and these feedbacks are considered by the IPCC to be uncertain.
2. If one assumes all warming over the past century is due to anthropogenic greenhouse forcing, then the derived sensitivity of the climate to a doubling of CO2 is less than 1C. The higher sensitivity of existing models is made consistent with observed warming by invoking unknown additional negative forcings from aerosols and solar variability as arbitrary adjustments.
Given the above, the notion that alarming warming is ‘settled science’ should be offensive to any sentient individual, though to be sure, the above is hardly emphasized by the IPCC.
Reconsidering the Climate Change Act Global Warming: How to approach the science.
Richard S. Lindzen
Program in Atmospheres, Oceans, and Climate
Massachusetts Institute of Technology
Seminar at the House of Commons Committee Rooms
22nd February 2012