by Judith Curry
Yale Environment 360 has just posted a forum with the same title as this post. I along with 7 other scientists provided a 250 word response to the question:
Do you think there is growing evidence that human-caused global warming is contributing to an increased incidence of extreme weather ?
The eight experts were:
- Kevin Trenberth
- Andrew Watson
- Roger Pielke Jr
- Kerry Emanuel
- Judith Curry
- Laurens Bower
- Gabriele Hegerl
- William Hooke
The individual essays are worth reading. I reproduce my own response below:
Judith Curry, chair of Georgia Institute of Technology’s School of Earth and Atmospheric Sciences.
The substantial interest in attributing extreme weather events to global warming seems rooted in the perceived need for some sort of a disaster to drive public opinion and the political process in the direction of taking action on climate change. However, attempts to attribute individual extreme weather events, or collections of extreme weather events, may be fundamentally ill-posed in the context of the complex climate system, which is characterized by spatiotemporal chaos. There are substantial difficulties and problems associated with attributing changes in the average climate to natural variability versus anthropogenic forcing, which I have argued are oversimplified by the IPCC assessments. Attribution of extreme weather events is further complicated by their dependence on weather regimes and internal multi-decadal oscillations that are simulated poorly by climate models.
I have been completely unconvinced by any of the arguments that I have seen that attributes a single extreme weather event, a cluster of extreme weather events, or statistics of extreme weather events to anthropogenic forcing. Improved analysis of the attribution of extreme weather events requires a substantially improved and longer database of the events. Interpretation of these events in connection with natural climate regimes such as El Nino is needed to increase our understanding of the role of natural climate variability in determining their frequency and intensity. Improved methods of evaluating climate model simulations of distributions of extreme event intensity and frequency in the context of natural variability is needed before any confidence can be placed in inferences about the impact of anthropogenic influences on extreme weather events.