A very interesting thread. A couple of observations which I'd be grateful for Dr Dave (or anyone else) to comment upon:
(a) There is incontrovertible evidence that global CO2 levels have increased substantially over the last 150 years (and are continuing to increase, although the rate is slowing). The evidence that this change has resulted in global temperature increases over the same period is much thinner.
(b) Models of the earth's climate are still pretty crude. One of the biggest problems is lack of computing power which forces the use of very coarse grids (around 1km square) which can take no account of smaller-scale phenomena such as clouds. Another problem is our lack of understanding of how the climate actually works! Estimates of future global warming amount (IMHO) to little more than a best guess.