Since I have a bit of free time, I thought I would expand a little on my Review of Roger Pielke Jr’s book about Disasters and Climate Change. As I mentioned in my earlier post, there were a number of things I disagree with, so thought I would expand a little on those here.
One thing that should be stressed is that what the book was mostly highlighting is that there is no indication that trends in disaster losses are due to human-caused climate change. This does not mean that we have not been able to attribute changes in some extreme events to human-caused climate change, because we have; the book is focusing on trends in disasters, not trends in the extreme events themselves.
Of course, that we may not be able to detect a trend in disaster losses that is due to human-caused climate change, does not mean that there is no such trend. However, the book argues that a signal that may exist, but which cannot be detected, is indistinguishable from a signal that does not exist. The book points out that God, aliens, and celestial teapots are also examples of things for which we have no evidence, but that we might want to believe do exist.
The problem, though, is that climate change is clearly happening and is predominantly being driven by our emission of greenhouse gases into the atmosphere. It’s already changing the conditions associated with extreme events and, in some cases, we’ve even detected a climate change related influence in some of these events. It may well be that other factors are dominating trends in disaster losses, but it would be remarkable if climate change was having no impact at all. I don’t think that this means that we should assume that human-caused climate change has contributed to some of the trend in disaster losses, but does – in my view – mean that we should be cautious of assuming that the lack of a detectable trend means that there is no trend. Even if we can’t detect something now, it seems very likely that we will in the future if we continue to dump CO2 into the atmosphere.
The other thing I was going to discuss was the argument against single event attribution. The suggestion is that this abandons the IPCC framework, which involves detecting trends over climatologically relevant timescales, and then trying to establish if anthropogenically-driven climate change was a cause of this trend. The IPCC, however, is simply an organisation that produces synthesis reports; it doesn’t – as far as I’m aware – have any mandate to specify appropriate scientific methodology. Also, single event attribution is an entirely reasonable thing to do. You consider the conditions associated with an extreme event, try to determine if these conditions could have been influenced by human-caused climate change and, hence, how this may have influenced the extreme event itself. Arguing against this is essentially arguing against doing physics. Patrick Brown has a nice post that briefly discusses this and presents an illustrative video.
As usual, this post is now too long. I wanted to finish by highlighting an earlier post in which I discuss extreme events and anthropogenic emissions and argue that formal attribution is not really all that relevant; we don’t really need to do some kind of formal attribution study to be quite confident that our emission of greenhouse gases into the atmosphere will probably influence extreme events. Understanding how it will do so, and the likely impact, clearly is important, but that’s somewhat distinct from demonstrating an anthropogenic cause.
Signal, Noise and Global Warming’s Influence on Weather – post by Patrick Brown.
Extreme events and anthropogenic emissions. – earlier post about attributing anthropogenic emissions to trends in disaster losses.
Economic losses from US hurricanes consistent with an influence from climate change – a paper by Estrada, Wouter Botzen and Tol estimat[ing] that, in 2005, US$2 to US$14 billion of the recorded annual losses could be attributable to climate change, 2 to 12% of that year’s normalized losses.