Perhaps we can sit down and discuss this climate change thing like the adults we are? Put the Delingpoles over here, the vilenesses that are Greenpeace, FoE and the rest of the forward-to-the-Middle-Ages crowd over there, and in that vast howling wasteland between the two positions discuss what we really know and what we ought to do about it?
Start with the simple fact that there are really only two important things we know about the entire idea. The first of these is that the direct effect of a doubling of atmospheric CO2 is trivial, something simply not to get worried about. Yes, we convert all the methane, NOx and all the rest into their CO2 equivalents, giving us not CO2 but CO2-e. And we know very well what the effect, directly, of a doubling of this from pre-industrial levels will be. A 0.7 degree rise in average temperature. This is simply straight physics and it is indeed highlighted in all of the IPCC reports. Less than the difference between Yorkshire and Cornwall, possibly than Somerset and Cornwall. At this level, quite frankly, who gives a damn?
The second thing we know absolutely is that this is not the end of the story, for there are feedbacks, and the really important thing is that we don’t know where they will lead. Feedbacks are all of the processes started by that 0.7 degree warming, and which then amplify (positive feedbacks) or dampen (negative feedbacks) that initial direct effect of the CO2. You can take your pick from an improbably long list: sea ice melting reduces reflection of light back out into space, allows the ocean underneath to be warmed: a positive feedback. More CO2 increases plant growth (which is why commercial greenhouses pump the stuff in) which leads to more humus formation and thus more carbon locked up in the soil: a negative feedback.
The cumulative effect of all of these feedbacks is something we simply do not know. We don’t even know what all the feedbacks are; and of those we do know about, we’re not sure in which direction they move. While there are some reasonable guesses about what the total number and direction of them all added together, we’re not certain whether that total effect is positive or negative.