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Ursprungligen postat av Bjorn-Ola
Frågade herrarna vid JREF om detta och ett av svaren jag fick var detta:
"Well, the main factor continue to be the temperature of the sea in the regions where hurricanes generate, and that is going up, but slowly, though cyclical variation can provide up to a decade of -just relative- apparent calm. That is why there are no hurricanes in the Southern Hemisphere -except the first one in history, Cyclone Catarina, in 2004-. But in the same way hurricanes made their début in the Southern Hemisphere, hurricanes have an slight increasing decadal trend in the Northern Atlantic.
Be alert as denialists tend to use 10-15 years period for "long term" trends carefully selected to show what they want. They also use moving averages adapted to avoid including unfavourable events.
Also as an effect of global warming there are an increasing number of events involving a high pressure creating blockages. This makes the hurricanes to move slowly near coastal zones what increments the size of surges. If Sandy is an example of something, that'd be it.
Look this subject up in SkepticalScience. You can point to the fact that cyclone activity in medium and high latitudes is clearly increasing, as the "less difference" in lower latitudes becomes a more abrupt thermal gradient in higher ones. "