So how about the Frankenstorm?
Here the waters get muddied. There is a hierarchy of weather events which scientists feel they understand well enough for establishing climate change links. Global temperature rises and extreme heat rank high on that list, but Hurricanes rank low. As the IPCC special report on extreme events put it “There is low confidence in any observed long-term (i.e., 40 years or more) increases in tropical cyclone activity (i.e., intensity, frequency, duration), after accounting for past changes in observing capabilities.”
The reasons for “low confidence” are manifold. Some part of the caution comes from the complexity of the problem, and some part comes from the lack of good data before the satellite era (about 1970). Thus, many climate scientists will not want to go out on a limb for hurricanes. They just don’t have the tools to make strong inferences.
This is not to say progress isn’t being made. One thing that does seem clear is that warmer oceans (a la global warming) mean more evaporation, and that likely leads to storms with more and more dangerous rainfall of the kind we saw with Hurricane Irene last year. In addition, a paper published just last month, used records of storm surges going back to 1923 as a measure of hurricane activity. A strong correlation between warm years and strong hurricanes was seen. Thus if you warm the planet, you can expect more dangerous storms.
Which brings us to our bottom line. The science of climate attribution is very exciting and full of cool, new ideas. It has already provided us with first steps towards more precision in understanding how climate change is changing climate now, already. For hurricanes, however, sticking to the science means it is still hard to point to an individual storm and say, yes! Climate change! A more reasoned approach is to take the full weight of our understanding about the Earth and its systems and go beyond asking if any particular event is due to global warming or natural variability. As Kevin Ternbeth of NCAR says “Nowadays, there’s always an element of both.”
Sorry Meggie! Try again.