The Intergovernmental Panel on Climate Change does not seem to be an irresponsible organization, and I know of no obvious reason to suspect that it is involved in any shenanigans of the CRU variety. At the same time, IPCC does not do its own research; it is dependent upon the research of others, and therefore upon the scrupulousness of others. Nonetheless, they write: ‘The observed widespread warming of the atmosphere and ocean, together with ice mass loss, support the conclusion that it is extremely unlikely that global climate change of the past 50 years can be explained without external forcing and very likely that it is not due to known natural causes alone.’ (That ‘very’ is an escalation from their previous position of just ‘likely.’) Having no scientific basis to disregard this conclusion, and no strong basis to suspect IPCC’s honesty, we ought to consider this claim carefully and sympathetically.