evidence: The Intergovernmental Panel on Climate Change asserts the conclusion that most (more than 50 per cent) of the post-1950 global warming is due to human activity, chiefly greenhouse gas emissions and land use change. But it does not survey its own contributors, let alone anyone else, so we do not know how many experts agree with it. And the statement, even if true, does not imply that we face a crisis requiring massive restructuring of the worldwide economy. In fact, it is consistent with the view that the benefits of fossil fuel use greatly outweigh the climate-related costs. One commonly cited survey asked if carbon dioxide is a greenhouse gas and human activities contribute to climate change. But these are trivial statements that even many IPCC skeptics agree with. And again, both statements are consistent with the view that climate change is harmless. So there are no policy implications of such surveys, regardless of the level of agreement. [...] Looking into further detail there are other interesting ways in which the socalled experts are unaware of unresolved discrepancies between models and observations regarding issues like warming in the tropical troposphere and overall climate sensitivity.