by Judith Curry
Better models are needed before exceptional events can be reliably linked to global warming. – Nature
Last week, a Workshop was held at Oxford University on Attribution of Climate and Weather Extremes: Assessing, Anticipating, and Communicating Climate Risks. The website for the Workshop is [here], but it is not very informative.
Nature has a very interesting editorial on the Workshop, some excerpts (JC bold):
So lawyers, insurers and climate negotiators are watching with interest the emerging ability, arising from improvements in climate models, to calculate how anthropogenic global warming will change, or has changed, the probability and magnitude of extreme weather and other climate-related events. But to make this emerging science of ‘climate attribution’ fit to inform legal and societal decisions will require enormous research effort.
Event attribution is one of the proposed ‘climate services’ — seasonal climate prediction is another — that are intended to provide society with the information needed to manage the risks and costs associated with climate change.
At a workshop last week in Oxford, UK, convened by the Attribution of Climate-related Events group — a loose coalition of scientists from both sides of the Atlantic — some speakers questioned whether event attribution was possible at all. It currently rests on a comparison of the probability of an observed weather event in the real world with that of the ‘same’ event in a hypothetical world without global warming. One critic argued that, given the insufficient observational data and the coarse and mathematically far-from-perfect climate models used to generate attribution claims, they are unjustifiably speculative, basically unverifiable and better not made at all. And even if event attribution were reliable, another speaker added, the notion that it is useful for any section of society is unproven.
Both critics have a point, but their pessimistic conclusion — that climate attribution is a non-starter — is too harsh. It is true that many climate models are currently not fit for that purpose, but they can be improved. Evaluation of how often a climate model produces a good representation of the type of event in question, and whether it does so for the right reasons, must become integral to any attribution exercise. And when communicating their results, scientists must be open about shortcomings in the models used.
It is more difficult to make the case for ‘usefulness’. None of the industry and government experts at the workshop could think of any concrete example in which an attribution might inform business or political decision-making. Especially in poor countries, the losses arising from extreme weather have often as much to do with poverty, poor health and government corruption as with a change in climate.
RealClimate also has a post on the Workshop. They answer the criticism that the whole exercise is pointless, in the following way (JC bold):
Do the critics (and Nature sort-of) have a point? Let’s take the utility argument first (since if there is no utility in doing something, the potentially speculative nature of the analysis is moot). It is obviously the case that people are curious about this issue: I never get as many media calls as in the wake of an extreme weather event of some sort. And the argument for science merely as a response to human curiosity about the world is a strong one. And if these changes can be laid at the feet of specific climate drivers, then they can certainly add to the costs of business-as-usual scenarios which are then often compared to the cost of mitigation. Therefore improved attribution of shifts in extremes (in whatever direction) have the potential to change cost-benefit calculations and thus policy directions.
JC comments: In agreement with the Nature editorial, I have written numerous previous points on why I think this exercise is pointless:
As per the RC essay, the rationale for attempting this seems to be driven by scientists thinking that this would be useful for influencing policy directions. To claim that the public and media interest in this is pure ‘curiosity’ (e.g. is there life on Mars) because of the large media interest surrounding this issue, seems naive at best; this interest is almost certainly driven by the interest of issue advocates in using extreme events to argue for mitigation policies.
People at the workshop from the insurance sector, lawyers, and government policy makers apparently see no use for these attribution exercises. Nevertheless, extreme event attribution is at the heart of the ‘climate service’ concept (which thankfully is still at best an unrealized concept). There has been a lot of wishful thinking (i.e. climate models are capable of attributing the causes of extreme events) and circular logic in terms of what the public and decisions makers need and want in trying to pass this stuff off as ‘climate services.’
Kudos to Nature for their insightful comments on this.