In the aftermath of the devastating 2005 hurricane season, the following soundbite was repeated incessantly, packaged in various ways, on every network news station by head meteorologists with impressive four-letter acronym's after their names:
NOAA There is consensus among NOAA hurricane researchers and forecasters that recent increases in hurricane activity are primarily the result of natural fluctuations in the tropical climate system known as the tropical multi-decadal signal.
It sounded credible, it came from experts, it was reassuring--it was also known to be highly suspect. The view put forward indicated a consensus that simply didn't exist. To be fair, even some of the natural cycle people at NOAA were said to be uncomfortable with it. We've also since learned that at the same time this misinformation was being doled out to a nervous public, dissenting views were being censored at other institutions by a heavy handed White House, often enforced by hand-picked 'minders.' Even more disturbing, at the time carefully selected NOAA spokespeople were making the decadal cycle pronouncement on national news stations, research indicating that climate change was producing more intense storms was growing.
A new study by Professors Michael Mann (Realclimate) and Kerry Emanuel (MIT) adds even more weight to the idea that human-caused increases in sea surface temperatures (SSTs) are responsible for higher intensity hurricanes:
Link--Human induced climate change, rather than naturally occurring ocean cycles, may be responsible for the recent increases in frequency and strength of North Atlantic hurricanes, according to Penn State and Massachusetts Institute of Technology researchers. "Anthropogenic factors are likely responsible for long-term trends in tropical Atlantic warmth and tropical cyclone activity," the researchers report in an upcoming issue of the American Geophysical Union's EOS.
Mann and Emanuel's work is further confirmation of the growing scientific consensus: Human activity is warming the atmosphere and ocean; warmer seas mean more powerful storms. A cyclonic storm that wouldn't have made it to a Cat 1 hurricane feeds on the warmer water and blooms into a Cat 3, or what would have only been a Cat 3 might become supercharged to a Cat 5. The warmer SSTs also work their way down into the water column; the water that is churned up in the wake of a hurricane is thus warmer than it would have otherwise been. This negates a natural dampening effect and means that storms which hover in one spot can now maintain or gain intensity. And storms following the recent track of a previous one can grow do likewise for the same reason. The end result of all of this means more intense storms and longer lasting ones. I.e., hurricanes that are more powerful when and if they make landfall.
Mann and Emanuel also conclude that in the recent past, aerosol pollutants which contribute a minor cooling effect for the globe on the average, but a very strong cooling effect in the late summer and early fall over the tropical Atlantic region where Hurricanes are formed, appear to have masked much of the warming produced by greenhouse gases. But aerosol pollutants are losing to GHGs as their production is tapering off, and global warming is increasingly winning out over the offsetting regional cooling effect. One likely result will be... more powerful hurricanes.
This graph says it all (Enlarge): The period between 1940 and 1975 represents the time when aerosols may have been temporarily dampening the warming effect of GHGs. The more recent period would indicate that GHGs have overwhelmed the global cooling effect. The sobering possibility is that the break-down of the balance between cooling and warming represents only one tipping point out of several, all of which are contributing to an increase in global temperatures and tropical Atlantic sea surface temperatures. Those tipping points in toto form the basis for the truly dire possibility that global temperature will increase dramatically over the next two decades alone. Source: NASA GISS
No doubt industry shills will seek to discredit this new data and perhaps even proclaim that aerosol pollutants, often oxides of sulfur and nitrogen, are therefore 'good.' I asked Michael Mann about that idea; he responded in part, "Aerosol production has leveled off. The warming due to GHGs continues unabated. So the global GHG warming is increasingly winning out over the regional aerosol cooling, and this is responsible for the upsurge in tropical Atlantic SSTs. Polluting the atmosphere to mitigate global warming would probably destroy our environment twice as fast. We'd have to pollute at an ever accelerating rate to offset the continued warming. A Faustian bargain if there ever was one."
In addition to being unhealthy in themselves, these aerosols often contain traces of methyl mercury and other toxic compounds which accumulate in the biosphere. They contaminate the air we breathe, the water we drink, and the food we eat. Sulfur and nitrogen dioxide are also the essential precursor for acid rain.
Anyway, regarding hurricanes and this season, we may get lucky this year. Large hurricanes may miss the US coast, strike in relatively unpopulated areas, or not form with the frequency predicted. But this is just one season. We cannot count on luck each and every year, especially as the underlying factors appear to be increasing. We are playing Russian Roulette with catastrophic hurricanes as the bullet and America's major coastal cities, from the southern tip of Texas to New York City, as the participants. It's just a matter of time before that random spin of the barrel lands on a loaded chamber ... or two.
If you wish to directly combat right-wing propaganda, get educated, vote modestly with your wallet, and be entertained all in one shot and all in two hours, go see Al Gore's movie, An Inconvenient Truth. Lindsay has a personal review of the film here and John has a round-up of other reviews here.
Next week's Science Friday will come straight from YK 06 and feature material from the YK Science Panel! Have a great weekend!