The basic point here is a good one, and it's obviously right as it applies to evolution and very likely to AGW as well, though I know very little about that and rely entirely on the fact of the scientific consensus in forming my opinion. But at the same time it is important to keep in mind that just because someone has worked hard and offered you the best evidence that they could be reasonably expected to muster under current circumstances, that doesn't necessarily mean that they have come anywhere near proving the case.