James Hansen at NASA has been the chief perpetrator of the nonsense known as anthropogenic global warming (AGW). His former boss, Dr. John S. Theon, expressed his opinion of Hansen's work in a recent email to a congressional committee:
Yes, one could say that I was, in effect, Hansen’s supervisor because I had to justify his funding, allocate his resources, and evaluate his results. I did not have the authority to give him his annual performance evaluation. He was never muzzled even though he violated NASA’s official agency position on climate forecasting (i.e., we did not know enough to forecast climate change or mankind's effect on it). He thus embarrassed NASA by coming out with his claims of global warming in 1988 in his testimony before Congress.
My own belief concerning anthropogenic climate change is that the models do not realistically simulate the climate system because there are many very important sub-grid scale processes that the models either replicate poorly or completely omit. Furthermore, some scientists have manipulated the observed data to justify their model results. In doing so, they neither explain what they have modified in the observations, nor explain how they did it. They have resisted making their work transparent so that it can be replicated independently by other scientists. This is clearly contrary to how science should be done. Thus there is no rational justification for using climate model forecasts to determine public policy.