The conference last week in Exeter on “Avoiding Dangerous Climate Change” grew out of a speech by UK Prime Minister Tony Blair. He asked “What level of greenhouse gases in the atmosphere is self-evidently too much?” and “What options do we have to avoid such levels?”. The first question is very interesting, but also very difficult. As Roger Pielke has noted the conference organisers actually choose three “key questions”:
- For different levels of climate change what are the key impacts, for different regions and sectors, and for the world as a whole?
- What would such levels of climate change imply in terms of greenhouse gas stabilisation concentrations and emission pathways required to achieve such levels?
- What technological options are there for achieving stabilisation of greenhouse gases at different stabilisation concentrations in the atmosphere, taking into account costs and uncertainties?
It is worth thinking about the difference between the initial aim and the “key questions” chosen. Question 1 is essentially IPCC WGII impacts); question 2 is firmly WGI (how-much-climate-change); question 3 is fairly WG III (mitigation, including technical options). I guess they switched questions 1 and 2 round to avoid making the identification too obvious. The conference steering committee report makes it very clear that they are building on the IPCC TAR foundation.
All in all it would seem that the bold vision of the politicians has been tempered by the conference organisers into something more manageable – a set of questions that can be discussed within the usual scientific framework and by the usual people. And probably that was sensible, because the initial question really is very hard – not merely because all the science isn’t in, but because even if it was what is “dangerous” is probably a political rather than scientific question. And this was a largely scientific meeting.
So, what’s new? On the impacts front, the final report says that there is more clarity and less uncertainty since the TAR, which is what you would hope for after 4 years of research. They identify a few “thresholds” that are dangerous for certain processes – 2.7 ºC local for melting Greenland; coral bleaching above 1 ºC global. Extremes, and the 2003 european heatwave get a mention. On climate change, they note that restricting the global temperature change to 2 ºC with a fair degree of confidence would require stabilisation at 400 ppm CO2 equivalent (CO2 itself is at 380 already, but “equivalent” includes other GHG’s and the negative effects of sulphates; see here for more). If you were prepared to accept more risk of exceeding 2 ºC then 550 ppm would be possible. For technical options, they note that the IEA predict a 63% increase in CO2 levels by 2030, in line with IPCC estimates. There are a whole raft of options that could be taken to reduce emissions, and they do mention the word “nuclear”.
All in all, it looks like progress as normal. In summary, they note that work is needed on both mitigation and adaption – which is to recognise that climate change is occuring and will continue, although possibilities for slowing it exist.
To pick out some of the science, there is the perennially interesting “will global warming cause cooling” bit that people love so much because it seems paradoxical. This is the “thermohaline circulation (THC) shutdown” or slowdown, caused by freshening of the North Atlantic. Of course it wouldn’t (at its worst) lead to global cooling, it would mostly impact Northern Europe. And the IPCC TAR said even in models where the THC weakens, there is still a warming over Europe (because the overall warming outweights the local cooling). This still seems to be true. The conference was presented some results showing what happens if THC shutdown is artifically induced (by Richard Wood), and various attempts to explore the probability of a collapse, but coupled AOGCMs seem to be quite resilient to a total collapse. From impacts, they mention that “resilient” societies are better able to survive climate stresses – for example, they downplay the oft-mentioned risk of malaria spreading under increasing temperature: the increase expected is small compared to the total number; all it means is that existing efforts to combat malaria should be strengthened.
And finally, since it gets a mention in the report, there are two possible errors to make, apparently labelled Type 1 and Type 2. Type 1 is excess caution, leading to damage by unnecessary action restricting development. Type 2 is insufficient action, leading to damage from climate change. In the face of uncertaintly, it is very hard to steer a true path avoiding these two errors, but it appears that we should be tilting towards taking action.
The conference generated a lot of press coverage (thanks Het). Nature said UK climate meeting calls for action; New Scientist said Climatologists pursue greenhouse gas danger levels and Only huge emissions cuts will curb climate change. The BBC told us of Scientists’ grim climate report, that “The risks from global warming are more serious than previously thought”. The Guardian warned of A grim assessment of the global cost for each degree rise in temperature and the Manila Times says Evidence indicates climate change already here, which is a mild strengthening of what the IPCC TAR told us. The reporting seems reasonably fair – slightly sexed up headlines, as usual, but the text of the articles quite faithful to the conference.