Simon Anthony sends this report of Myles Allen's recent lecture at Oxford.
Myles (I think he'd prefer I call him "Myles" rather than Prof Allen as most people in the audience seemed to refer to him thus) is prof of geo-system science in the school of geography and the environment and heads the climate dynamics group in physics dept, both in Oxford. His main interest has been in attribution of aspects of climate, particularly "extreme events" to human activities. Recently he's been working on how to use scientific evidence to "inform" climate policy.
The lecture's title comes from Isaiah Berlin's contrast between "negative" and "positive" liberty. These can be (slightly) caricatured as, respectively (and perhaps contrarily) freedom from constraints (eg tyranny) and freedom to do particular things (eg vote for the tyrant). Amongst other things, Berlin was concerned about the possible abuse of positive liberty in which the state prescribes what is permitted rather than ensuring the conditions in which individuals were free to make their own choices.
Myles contrasted two extreme views of how to address climate change: either continue as currently so 0.001% of the world's population choose to benefit from emissions of CO2 and the poorest 20% involuntarily suffer the consequences or halt emissions and so demolish the capitalist, liberal, market system. In conversation afterwards he accepted this was a rhetorical flourish rather than a genuine choice. 0.001% of the world's population is ~700,000. He said this number was those who profited directly from extraction and burning of fossil fuels. But it omits shareholders or citizens who benefit from taxes paid by oil cos etc. And it omits those who, for example, drive or keep warm or light their houses. If these people were included, the number of beneficiaries would likely be rather more than the number suffering. So it seems more than a little disingenuous to characterise the "sides" in these terms. In any case, rather than have states impose strict controls, Myles wanted to investigate means by which emissions could be voluntarily curtailed and suffering compensated through negative liberty.
So, he says, assume that IPCC's predictions are correct but it'll be 30 years before confirmation. What measures can be taken to reduce CO2 emissions? Offsetting doesn't work because what counts is cumulative emissions, not the rate. Centrally imposed limits would potentially mean big opportunity costs as beneficial activities might not be undertaken. Is there instead some means by which the impacts can be traced back to CO2 emissions and the originators made to pay (cf Deep Water Horizon)?
An essential component of any such scheme is that harm caused by climate changes should be correctly attributed to fossil fuel CO2 emissions. If that were possible then, on a pro rata basis of some kind, those companies responsible for the emissions and which had directly benefitted from extraction and burning of fossil fuels (oil, coal, gas, electricity, car manufacturers, airlines...) could be penalised and the proceeds distributed to those who were judged to have suffered.
Now Myles (I think somewhat inconsistently) seemed to accept that climate predictions for 30 years into the future were unverifiable, unproven and unreliable (perhaps not surprising when, as Richard Betts confirmed in another thread, even when the Met Office has the opportunity to assess its 30+-year temperature anomaly predictions in, for example, forecasts made in 1985, it chooses not to do the tests. One can only speculate as to why that might be.) He also accepted that the public might justifiably not believe the assurances of climate experts, particularly given the patchy record of mighty intellects in predicting the future (examples he gave were Einstein post-war seeing imminent disaster unless a world government was immediately set up; a Sovietologist who in the mid-1980s confidently predicted the continuing and growing success of the Soviet Union; 30-year predictions of US energy use which turned out to be huge overestimates and Alan Greenspan's view that derivatives had made the financial world much secure. I'd have been tempted to add Gordon Brown's (or George Osborne's) economic predictions but time was limited.) There was very little reason to expect people to believe in the extended and unfeasible causal chain leading to predictions of temperatures in 30 years time
Instead Myles proposed that the frequency and pattern of "extreme" events was now well enough understood that the effect of CO2 emissions could be reliably separated from natural variations. He gave various examples of how models had been validated: the extent of human influence on the European heatwave of 2003 has been "quantified"; the Russian heatwave of 2010 was within the range of natural variation; model predictions of annual rainfall in the Congo basin matched uncannily well the "observations" (Myles himself initially doubted the extraordinarily good match, although he now accepts it's genuine. However, the "observations" weren't all one might expect because conditions for meteorologists in the Congo are understandably difficult, so there aren't any actual measurements. Instead an "in-fill" procedure was used to extend readings from safer locations to the Congo basin. I asked whether this agreement between a model and, um, another model was really a good test of either. Myles assured me that both models were reliable and show good agreement with measured data in, for example, western Europe. Still, an odd way to illustrate reliability of model predictions.).
So although it wasn't possible reliably to predict climate to 2050, current near-term regional forecasts may be good enough to show that the probability of extreme events was changed by CO2. In any case, the people who believe they've been adversely affected by climate change are free to take legal action against the companies they believe are responsible. Myles foresaw such litigation growing as the effects of climate change became more apparent.
An obvious question arises, rather like the "dog that didn't bark": if the evidence for the effect of AGW on extreme events is as strong as Myles and others claim, why haven't class actions already been brought, particularly in the US? "Ambulance chasing" lawyers aren't renowned for their reticence but so far there has been no action of great significance. I don't think it's wild speculation to suggest that lawyers have examined possible cases but haven't yet thought the evidence strong enough to make it worth while proceeding. Of course at some stage such cases will come to court and then Myles may find that his hope that they'll change the "climate" of debate will cut both ways. Because if a major class action against, say, oil companies claiming compensation because the 2003 European heatwave was due in part to CO2 emissions, was brought and failed, it would be a major setback to hopes for international laws to limit further emissions. While litigation won't advance science, it could be very politically significant - as well as entertaining - to have the arguments for AGW tried in court.
Finally, having been to three of the Wolfson lectures on climate change, I'd like to add a couple of observations. First, although all the speakers talked about the evidence for AGW, not one of them mentioned hockey-sticks. Stocker came closest when he said that current temperatures were the warmest for 500 years but didn't venture an opinion on the medieval warm period. I wonder whether it's too much to hope that the more scrupulous climate scientists are distancing themselves from the petulant antics and inept science of hard-core "Team" members. And second, two of the three speakers (Wunsch and Allen) said that there was little reason for people to believe that 30-year climate predictions were reliable. So perhaps the better climate scientists will stop relying on magical trees and statistics to make up the past and dubious models for scary futures. Instead they might try to do what Myles advocates and concentrate on shorter term understanding of the climate which might at least be testable.