It sure is quiet across the tropics - everywhere. The Western Pacific, which normally sees about 30 named storms per season, has had only a single named storm in June, and that one developed just yesterday. The East Pacific hurricane season began on May 15th, and not one named storm has formed as of June 19th. As of 1AM CDT this morning (June 19th), this is the latest start to the East Pacific hurricane season since detailed records began in 1970.
Globally, tropical cyclone activity remains at a 30-year low, similar to levels in the 1970s, and activity continues to decline. Detailed records of global tropical cyclone intensity are sketchy at best prior to the late 1970s, so it’s hard to say just how low current activity is compared to several decades ago. And we probably underestimated the intensity of many tropical cyclones prior to the age of modern recon, Doppler Radar and GPS dropwindsondes deployed by recon, so it’s likely that current global activity is even lower compared to the record of the 1970s.
We measure global tropical cyclone activity by the total Accumulated Cyclone Energy, or “ACE”. ACE for a tropical cyclone is calculated by squaring the max wind speed at each 6-hour advisory interval and then dividing the end result after a cyclone dissipates by 10,000. So ACE is a good measure of the intensity of a tropical cyclone and its duration. The median ACE for the Atlantic Basin since 1950 is about 90. The most active season during that period, 2005, had an ACE of 248. The season with the lowest ACE since 1950 was 1983 with a total of only 17. Last year’s ACE was 145, making the 2008 Atlantic Basin season a good bit above normal. But the Atlantic Basin was the only ocean with above normal activity in 2008. Most other regions had well below normal activity over the past 2 years.
What’s going on? Why the big drop in ACE the past few years? For one thing, the Earth’s climate has actually begun to cool over the past two years. Cool La Niña conditions have prevailed across the Tropical Pacific for the past year, adding to the cooling of the climate. Cool water means less intense tropical cyclones with shorter lifespans. The last significant cooling trend in the Earth’s climate began during the mid 1940s and continued until the late 1970s when the Atlantic began to cool considerably (cool Atlantic Multidecadal Oscillation which began in 1970 and continued through 1994). The previous cooling began during the middle of the last warm Atlantic cycle which began in 1926 and ended in 1969. The current warm Atlantic cycle began in 1995 and will probably continue for another 10-20 years. As the Atlantic temperatures pass the peak, we should expect global climate cooling to continue in the coming years, much like the period from the late 1940s through the late 1970s.
A cooling climate is good, right? Perhaps not. If one checks hurricane activity across the Atlantic Basin in the 1940s, 1950s and 1960s (during the global cooling trend), this was a period of significantly increased major hurricane landfalls across the U.S., particularly from Florida northward through the Carolinas. So cooling may not diminish the impact from hurricanes, at least not in the short term. And as the Earth’s climate cools, farmers will experience shorter and shorter growing seasons. For those of you concerned about global warming, I encourage you to read an article published in Newsweek on April 28, 1975:
http://www.denisdutton.com/cooling_world.htm
There was such concern about global cooling and the potential lack of food due to the shorter growing seasons back then that some scientists advocated the questionable idea of spreading soot across the Arctic ice sheet to help melt the ice to produce global warming! According to the article, scientists were “almost unanimous in the view that the trend will reduce agricultural productivity for the rest of the century.” That just goes to show you how well we can predict the Earth’s climate. I particularly liked the last sentence of the article - “The longer the planners delay, the more difficult will they find it to cope with climatic change once the results become grim reality.” That’s something to ponder as we consider taking drastic actions to counter the predicted impact of global warming.
Given the current state of the tropics, I think that there’s a good chance that we won’t see the first named storm in the Atlantic Basin until August. So enjoy the current lull in tropical cyclone activity while it lasts. And remember, even though we’re predicting only about 10 named storms this season, it only takes one hurricane hitting the wrong location (i.e., you) to make for a very bad year.
