Abstract: The subject of global warming has become so politicized that it is difficult for a scientist to evaluate what is true and what is not. I'll present a broad range of relevant evidence. As an example, I'll discuss the recent controversy over the "hockey stick" plot, and the recent Academy study, for which I was a referee. The greatest uncertainty in the discussion today is the relative size of human vs natural variation, and I'll present data that will help you understand the limitations of the analysis.