This report in the Guardian cites leading leftwing thinktank the Institute of Public Policy Research as saying that, according to the latest research at the Hadley Centre for Climate Change, the likely change in temperature by 2100 (under business as usual) will be 8 degrees C, as against ‘consensus’ estimates ranging from 1 to 5 degrees C . The argument is apparently based on claims that CO2 stored in the soil will be released with rising temperatures, producing a positive feedback.
I haven’t followed this up, and it seems surprising that such an obvious mechanism should have been overlooked. So I’m not suggesting that this report should be regarded as reliable. Rather, I want to use this report to illustrate a point I’ve made previously.
A lot of critics of Kyoto argue that, since there’s a lot of uncertainty about the estimates produced by the Intergovernmental Panel and Climate Change and similar bodies, we should ‘wait and see’. These critics tend to pounce on any study that produces an estimate lower than the consensus range to bolster their case.
This neglects the fact that uncertainty goes both ways. There’s a nonzero probability that the rate of warming could be lower than the range suggested by the best available estimates, but it’s equally possible that the rate could be higher. The best available estimates suggest we should do something now (Kyoto) and prepare to do a lot more in the future unless we get a favorable surprise.
In the case of global warming uncertainty actually strengthens the case for action because the damage costs are convex. That is, an increase of 4 degrees will do more than twice as much damage than an increase of 2 degrees and an increase of 8 degrees (the IPPR estimate cited above) would be utterly catastrophic. So, the more uncertainty there is, the stronger the case for action.
When there’s a lot of uncertainty, the important thing is not so much immediate action to reduce emissions as the creation of institutions and mechanisms that will allow large reductions to be made in future. With all its imperfections, the Kyoto agreement is the only process that offers any possibility of progress in this respect.