On November 17, the House Committee on Science and Technology held a hearing on climate change. In a departure from past practice, a climate realist was included on each of the three panels. You can watch the entire hearing on C-Span. The witnesses’ statements are available at the committee’s site. One of the realist witnesses was Richard Lindzen of MIT, whose testimony is here. This brief excerpt sums up the essence of the global warming debate:
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.
The usual rationale for alarm comes from models. The notion that models are our only tool, even if it were true, depends on models being objective and not arbitrarily adjusted (unfortunately unwarranted assumptions).
However, models are hardly our only tool, though they are sometimes useful. Models can show why they get the results they get. The reasons involve physical processes that can be independently assessed by both observations and basic theory. This has, in fact, been done, and the results suggest that all models are exaggerating warming.