One of the major techniques of modern politics is to take every important event and tie it to the back of one's own particular hobby horse. One of the more ludicrous examples was the utterly absurd claims that the Asian tsunami was caused by global warming. Hence it was inevitable that we would begin to see articles today with titles such as "Brace for more Katrinas, say experts,"
from today's edition of Agence Press France. The anonymous author correctly observes that hurricane activity has intensified and looks likely to remain so for a while:
"Earlier this month, Tropical Storm Risk, a London-based consortium of experts, predicted that the region would see 22 tropical storms during the six-month June-November season, the most ever recorded and more than twice the average annual tally since records began in 1851."
The piece also notes,
"Already, 2004 and 2003 were exceptional years: they marked the highest two-year totals ever recorded for overall hurricane activity in the North Atlantic."
That is all quite true. Then the article moves on to consider a possible relationship to global warming, as has been posited by advocates of controls over greenhouse gas emissions:
"This increase has also coincided with a big rise in Earth's surface temperature in recent years, driven by greenhouse gases that cause the Sun's heat to be stored in the sea, land and air rather than radiate back out to space."
The characterization of the rise in the planet's surface temperature in recent years as "big" is certainly an exaggeration. However, the article does go on to point out that hurricane activity is cyclical and almost certainly always has been:
"But experts are cautious, also noting that hurricane numbers seem to undergo swings, over decades.
"About 90 tropical storms -- a term that includes hurricanes and their Asian counterparts, typhoons -- occur each year.
"The global total seems to be stable, although regional tallies vary a lot, and in particular seem to be influenced by the El Nino weather pattern in the Western Pacific."
These are very important observations. The article then outlines, at some length, the arguments of global-warming advocates who claim that g.w. is creating more intense hurricanes, if not more such storms overall:
"On the other hand, more and more scientists estimate that global warming, while not necessarily making hurricanes more frequent or likelier to make landfall, is making them more vicious."
The evidence the article adduces for this argument is coincidental and not causal, however, and is clearly highly speculative at this point. The piece says, for example, "'The intensity of and rainfalls from hurricanes are probably increasing, even if this increase cannot yet be proven with a formal statistical test,' Trenberth wrote in the US journal Science in June. He said computer models 'suggest a shift' toward the extreme in in hurricane intensities." That is to say, Trenberth believes it although there is no statistical evidence for it.
The article ends on that note, which is a pity because there is more to the story than that. Readers are not told, for example, that as an article in the forthcoming October issue of Environment and Climate News
mentions, a group of prominent climatologists and other experts on climate change has noted, "according to a century of National Hurricane Center
reports, the decade with the largest number of hurricanes to come ashore in the United States
was the 1940s, and that hurricane frequency has declined since then. They also cited data from the United Nations Environment Programme of the World Meteorological Association that hurricane frequency has declined since the the 1940s."
The ECN story, unlike the APF one, quotes the environmental scientists as observing that "centuries-old evidence, as well as computer models, suggest warmer periods may actually generate a decline in the number or severity of such storms."
The ECN story quotes James J. O’Brien, director of the Center for Ocean-Atmospheric Prediction Studies at Florida State University, as arguing that "the more likely cause of hurricane frequency might be found in variations in the Atlantic Ocean Conveyer, the movement of the warm Gulf Stream whose waters, taken from the South Atlantic, replace the cooler, sinking water in the North Atlantic.
"When the Conveyer is strong, O’Brien said, historic records have shown an increase in Atlantic hurricanes; when it is weak, so are the hurricane seasons. For a hurricane to grow stronger, it must keep moving over waters warmer than 80 degrees F, which leads some people to link global warming and the storms. But, he said, there’s no scientific evidence to show that such areas of warm water are increasing in size."