Pump Up The Volume  

I've muttered periodically about the link between global warming and the increasing frequency of various forms of heavy weather such as cyclones, hurricanes and typhoons, and how this is likely to affect oil production as we become more dependent on offshore based production as we pass over the peak (most of you have probably seen recent reports that the tallest wave ever measured was in the Gulf of Mexico last year during Hurricane Ivan, which damaged a number of rigs).

To a certain extent, this belief has been based on anecdotes and gut feeling as much as anything. While it seems to make sense, is there any empirical evidence to support it ?

Both RealClimate and WorldChanging have posts up today looking at the link between storms and global warming.

RealClimate says that there is no firm evidence linking frequency of storms to global warming yet, though there is a firmer link between the strength of the storms as the sea surface temperature rises.

There have been 7 Tropical Cyclones (TCs) already in this hurricane season. According to Gerry Bell from NOAA's, seven TCs during June and July is a new record. NOAA also forecasts a high hurricane activity for the remainder of the season, and time will show if this season will match the 2004 in terms of number of tropical cyclones. But we do not yet know if this constitutes an emerging trend - only hindsight after decades will tell.

Thus, the bottom line so far seems to be that sea surface temperatures play a role for the TC statistics (destructive power). The most dominant change in TC activity is related to natural cycles (on inter-annual and inter-decadal time scales), which we would call 'noise' in a trend analysis in which the trend would be the 'signal'. There is little evidence of a trend in the TC frequency, however there are some indications of a trend in the destructive capability of the TCs. Conlusions can differ depending what you look at: frequency, intensity, duration of storms (life times) or destructive potential. Emanuel suggests that the recent upturn in the tropical cyclones' destructiveness can have two explanations: increased level of intensity (consistent with discussions on Storms and Climate Change and Some recent updates) or longer cyclone life times.

WorldChanging's description is based on RealClimate's, with both posts referencing a recent article in Nature, summarised here in New Scientist.

The precise nature of the relationship between global warming and hurricanes remains the subject of debate. Although it's highly likely that increased atmospheric (and, as a result, ocean) temperatures has some effect on the location, frequency and/or intensity of hurricanes, a number of climate scientists remain hesitant to draw any specific conclusions about that effect. That's a wise course of action, in my view; it's important that, if climate scientists do present findings that global warming is increasing the threat from hurricanes, they do so in a way that is convincing to the broadest spectrum of climatologists.

That said, a growing number of climate researchers think that such a case is now being made.

The statistics for the southern hemisphere show that there has been a slight rise in numbers and intensity over the past 20 years, though the sample size probably isn't big enough to be significant.

As more and more offshore platforms go up on the North West Shelf and in the Timor Sea its worth keeping an eye on though, especially for whichever insurance companies cover the damage done to these by the weather.