this triggered a tax on dr. mann and the science behind his work, all documented in his book "the hockey stick and the climate wars." michael mann, you write that in mid 1990s, scientiststs were abe to begin to connectct the dototn climate chanange. could yoyou elaborate? >> we underststood the basic science of the greenhouse effect nearly two centuries ago. joseph fourier, the same guguy who discovered the law of heat conduction, understood that there was this greenhouse eeffect. so wewe've known for se time that the greenhouse effect exists and that we'rere increasg it through fossil fuel burning. bby the mid 1990s, we had reachd a level of formal certainly about that that we had not before reached. we could actually attach a number to it. in the second assessment report of the ipcc published in 1995, the ipcc concluded that there was now a discernible human influence on the climate. now, therere's an interesting storory there. the language woud have been n stronger than just discerernible, but the delelegas of cer