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Published online 30 January 2008 | Nature | doi:10.1038/news.2008.544
News: Briefing
Stormy weather
Experts still divided on the link between climate change and hurricanes.
Are rising temperatures favouring more and stronger hurricanes? A study published in Nature this week attempts to quantify the relationship between Atlantic hurricane activity and ocean temperature to help answer this question. Nature News examines where we are in the debate and what it means for us.
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Starting your stats at 1970 makes for a shamelessly contrived analysis. The powerful storms in the 1950s and 1960s weaken your argument, so just leave those years out, right? Plus, technology's enabled us to detect Atlantic storms earlier in their lifespan (easily explaining the 'longer-lasting storms' claim), and also to spot brief surges in strength for distant storms (helping to explain more storms reaching higher index levels). You've basically 'stacked the deck' to make the situation support your analysis, which is the way we used to do our physics labs in high school -- but backwards from the way real science goes. Note that seasonal storm strength has *decreased* over 50% since 2005. (Manipulating statistics is a whole lot easier than doing real science, and it makes better headlines; but do that and forfeit your credibility among scientists.)
I do not find the same facts as outlined in this article: for one, I do not find a "70% increase in category 4 and 5" storms. I recently completed an analysis of tropical storms in the North Atlantic and find no increase in number of intensity starting from 1966, the beginning of the satellite era. It is, however, possible to say there was an increase if you choose a starting date in the mid-1970s. Nor is there is an increase in storm days, track length, or individual storm power dissipation index. There has been an increase in the variance of these measures, but not their mean: this is consonant with the fact that changes in measurement instruments and practices have changed since 1966, but, of course, it is also consonant with actual physical changes. This paper will appear shortly in J. Climate. I repeated the analysis for world-wide tropical storms and came to the same conclusions. Plus, the measurement error in the Indian Ocean is very large and obvious until about, say, 1990. A draft of both papers can be had at my website wmbriggs.com/resume The world-wide paper is undergoing revision and will change (no results will, but my English was awful in the first draft).
I think that there are several other factors which could be contributing in some way to the intensity of storms and/or their frequency. For one thing the composition of the atmosphere is changing. There is a higher concentration of CO2 and a decreasing concentration of O2 (NOAA research data). In addition the concentration of both of these in the oceans are changing the overall composition of seawater. The H2O produced by burning fossil fuels ( CH4 + 2O2 -> CO2 + 2H2O) is potentially increasing the overall humidity (or water concentration) in the atmosphere and potentially maintaining such unnaturally high levels from sea level all the way up to the Troposphere. It is hard to believe, as the other two commenter's seem to be claiming, that such an overall change in composition of the atmosphere and ocean would have no effect on the frequency or severity of storms.
I'd probably concur with the third post's point, if the concentration of CO2 in question was more significant. (Earth's atmosphere is roughly 78% nitrogen, 21% oxygen, 1% argon, and less than 0.1% carbon dioxide.) You'd have to double the CO2 several times before you even reach 1%. Getting all apocalyptic about this is as ridiculous as saying ''our planet has a FEE-ver'' (from Algore's cheesy horror slide-show), when the temperature's only gone up a couple of tenths of one degree. (Yes, Al - you take your baby to the doctor when it runs a fever, but you don't call 911 when it's temp is 98.7 degrees...)
It’s a little bit ironic that the same commenter who is blaming others for “manipulating statistics†is himself presenting the facts in a way that suit him best. Yes, the concentration of CO2 in the atmosphere is in absolute terms very small, but isn’t that small amount largely responsible for the total greenhouse effect that makes the average surface temperature of the Earth about 33 K warmer that it would otherwise have been? It’s not the absolute numbers that count, but the relative impact.