Real Climate on IPCC
A helpful and sane analysis:
Contrarians will no doubt be disappointed here. The conclusions have been significantly strengthened relative to what was in the TAR, something that of course should have been expected given the numerous additional studies that have since been done that all point in the same direction. The conclusion that large-scale recent warmth likely exceeds the range seen in past centuries has been extended from the past 1000 years in the TAR, to the past 1300 years in the current report, and the confidence in this conclusion has been upped from "likely" in the TAR to "very likely" in the current report for the past half millennium. This is just one of the many independent lines of evidence now pointing towards a clear anthropogenic influence on climate, but given all of the others, the paleoclimate reconstructions are now even less the central pillar of evidence for the human influence on climate than they have been incorrectly portrayed to be.
The uncertainties in the science mainly involve the precise nature of the changes to be expected, particularly with respect to sea level rise, El Niño changes and regional hydrological change - drought frequency and snow pack melt, mid-latitude storms, and of course, hurricanes. It can be fun parsing the discussions on these topics (and we expect there will be substantial press comment on them), but that shouldn't distract from the main and far more solid conclusions above.
I've long been an advocate of empirically-based, market-friendly policies that ensure we do not damage the sacred inheritance of our planet. I wrote one of the first pamphlets arguing that conservatism and environmentalism are not just compatible but intertwined. It was for Margaret Thatcher in 1985 - and she promptly ignored all of it. I have long had an open mind on climate change, but an open mind now means, it seems to me, a clear, empirical conclusion. Climate change is happening, it is almost certainly man-made, although some doubt persists as to quite how deep and swift the change will be. I write this not as a statement of dogma but as a statement of the best inference from the data we now have. This is not - or should not be - a right-vs-left issue. It's a fact vs fantasy issue. Right now, the fantasists are those saying we have nothing to worry about. We do. The question is merely how best to adapt. A big increase in taxes on carbon is the obvious starting point. Once government sets incentives, the amazing ingenuity of the American marketplace will do the rest.