Reader DR sends these notes from A Meeting on Sustainability at the University of Oxford
'What can be said about future climate? Using observations to constrain the forecast and the implications for climate policy.'
Myles Allen introduced himself as a member of an endangered species, a climate scientist. He agreed that energy measures will be needed regardless of climate change, but wanted to argue that climate change is important. He said that climate scientists have recently been faced by many questions, both from sceptics and from the policy community, and said that most people are asking the wrong questions. It is clear, he said, that CO2 is rising and temperatures are trending upwards.
He showed a slide listing the issues raised by Climategate, and said that he had not read the emails, but none of the accusations have come to anything. In terms of data sharing, he said that Phil Jones only ‘crime’ (if there was one) was to use his professional judgement to distinguish between scientists on one hand and ‘activists and nutters’ on the other. Allen said that personally he receives numerous emails purporting to have disproved relativity or some such, and he worries that freedom of information legislation may be removing his right to ignore such communications. He said there was no problem with data sharing in climate science between climate scientists. Indeed he had emailed John Christy and Eduardo Zorita, and they said they had never had any problems obtaining data from Phil Jones. Allen also criticised the press, e.g. the BBC’s Newsnight airing criticism of software, which was not in fact temperature software despite the impression given in the programme.
Allen then turned to climate predictions. He showed that the prediction he made 10 years ago (Allen et al. 2000) was exactly right for the average temperature of the first decade of the 21st century. But, he said, some predictions have been too conservative. Arctic sea ice has retreated faster than predicted (he showed sea ice data up to 2008), and sea level rise is at the top end of IPCC predictions. The 2003 european heatwave caused perhaps 40-70,000 extra deaths, which he said could be termed an ‘industrial accident’ (for the fossil fuel industry). The challenge for climate scientists, he said, was to distinguish the impacts of climate change from weather fluctuation – one should not blame everything on climate change, but neither should one blame nothing. He mentioned the strong financial incentive to be a ‘victim of climate change’ – there is a $100bn fund available to those who can prove it.
What is dangerous climate change? Allen showed the figure of various impacts of different temperature increases [a variety of the first graph on this page: http://en.wikipedia.org/wiki/Effects_of_global_warming] and said that the main negative impacts would be avoided if total temperature increase was limited to 2 degree C (about 1.5 degrees C from where we are now), but we don’t know how to ensure this. He feels it is encouraging that there is far more of a consensus between countries that emission reductions are needed, even China agreed this (in principle) at Copenhagen. But, Allen feels that CO2 targets are the wrong approach. Science cannot tell us whether CO2 should be stabilised at 350 or 450ppm. He argued that the total amount of fossil fuel burned is crucial – the long term temperature response is similar whatever the rate of emissions – but we cannot stabilise temperatures below 2 degrees C increase if we produce more than a trillion tonnes of CO2 (see Allen et al, Nature, 2009, and TrillionthTonne.org).
Allen feels that Kyoto took policy in the wrong direction (see e.g. Prins and Rayner, The Wrong Trousers) and that the failure of Copenhagen is an opportunity – it is time to consider alternatives. He cautioned against geoengineering, including pumping CO2 out of the air after the temperature has increased. His models predict that removing CO2 might have unwanted effects on rainfall – there is a danger of ‘replacing warming with drying’ and increasing climate instability. We don’t have the modelling capacity, he said, to predict all of the consequences of geoengineering, so we should attempt to prevent CO2 emissions reaching the cumulative limit, by reducing usage and making carbon capture mandatory.