Huffington Post contributor Laurie David explains, with the rigor for which that site is known, how your SUV caused hurricane Katrina:

As the country continues to dissect the recent natural disaster, we might want to start considering what about the disaster wasn’t actually “natural” at all. Water temperatures in the Gulf of Mexico were “unnaturally” high. Human activity, the burning of fossil fuels, is causing global warming. Global warming is causing the oceans to warm. Warm oceans are steroids for storms. Katrina began as a category 1 hurricane near Florida; after reaching the 90 degree waters of the Gulf it turned into a category 5 monster storm.

The former talent agent fails to cite sources for her chain of assertions, especially her keystone: “Global warming is causing the oceans to warm.”

Similarly, Robert F Kennedy Jr also wrote in the Huffington Post:

Now we are all learning what it’s like to reap the whirlwind of fossil fuel dependence which (Mississippi Governor Haley)Barbour and his cronies have encouraged. Our destructive addiction has given us a catastrophic war in the Middle East and–now–Katrina is giving our nation a glimpse of the climate chaos we are bequeathing our children.

Do we know that fossil fuel burning => global warming => more hurricanes?

A 2001 article in Science — “The Recent Increase in Atlantic Hurricane Activity: Causes and Implications” — suggests that recent ocean warming trends are part of a recurring 30-40 year cycle, not any human-caused permanent increase.

A news article at National Geographic on that study’s findings said

Until now, the conditions responsible for the formation of tropical storms have been poorly understood. … By using a combination of satellite imagery, computer modeling, and high-tech monitoring of numerous factors—from sea-surface temperatures to atmospheric conditions—the team of scientists has identified a multi-decade pattern of likely hurricane activity. These long-term patterns can be classified as quiet, near normal, or active.

During the 20th century, a period of high hurricane activity occurred from the 1920s through the 1960s, followed by reduced activity from 1971 to 1994.

The researchers predict that we are now on the cusp of a 10- to 40-year shift toward increased frequency of hurricanes.

Here is a graph from the Science paper (their figure 2, also here) that shows there have been several decades-long swings in Atlantic sea surface temperatures since 1870:

Written by researchers at NOAA’s Atlantic Oceanographic and Meteorological Lab, the University of Miami, and the University of Colorado, the highly cited article says:

The numbers of major hurricanes and of Caribbean hurricanes, however, exhibit strong multidecadal variability. The late 1920s to the 1960s were very active, while both the 1900s through mid-1920s and the 1970s through the early 1990s were quiescent … Even with 1997 included, the mean number of major hurricanes and mean NTC for 1995-2000 are the highest of any consecutive 6 years in the 1944-2000 record. While this recent period spans only 6 years, it clearly belongs to a different low-frequency climate regime than the previous 24 years.

On the issue of whether Atlantic warming is caused by humans, the answer is that the 30-40 year cycle is far more important than any long term increase in average temperature:

One may ask whether the increase in activity since 1995 is due to anthropogenic (human-caused — ed.) global warming. The historical multidecadal-scale variability in Atlantic hurricane activity is much greater than what would be “expected” from a gradual temperature increase attributed to global warming.

There have been various studies investigating the potential effect of long-term global warming on the number and strength of Atlantic-basin hurricanes. The results are inconclusive. Some studies document an increase in activity while others suggest a decrease. Tropical North Atlantic SST (sea surface temperature) has exhibited a warming trend of ~0.3°C over the last 100 years; whereas Atlantic hurricane activity has not exhibited trendlike variability, but rather distinct multidecadal cycles as documented here and elsewhere. The extreme activity in 1995 has been attributed in part to the record-warm temperatures in the North Atlantic.

The possibility exists that the unprecedented activity since 1995 is the result of a combination of the multidecadal-scale changes in Atlantic SSTs (and vertical shear) along with the additional increase in SSTs resulting from the long-term warming trend. It is, however, equally possible that the current active period (1995-2000) only appears more active than the previous active period (1926-1970) due to the better observational network now in place. During the previous active period, only 1966-1970 had continual satellite coverage. Further study is essential to separate any actual increase from an apparent one due to more complete observations.

So David’s and Kennedy’s linkage of any “global warming” (as the environmental community uses the phrase) and hurricane activity does not work. Today’s high sea surface temperatures are not primarily human-caused, but are just part of the 30 – 40 cycle seen in the chart above.

Human activity might have long-term effects on climate but likely had no impact on the creation of hurricane Katrina. Contrary to the poorly reasoned Huffington posts, Katrina — and every other hurricane — was entirely “natural.”

—
Kennedy also writes in his post “Well, the science is clear. This month, a study published in the journal Nature by a renowned MIT climatologist linked the increasing prevalence of destructive hurricanes to human-induced global warming..” But really all the study said was that recent hurricanes have been more powerful than they should have been. This result has been questioned by reasoned critics, including scientists at NOAA — see here.

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This entry was posted on Wednesday, September 21st, 2005 at 12:17 pm by A Senior Administration Official and is filed under Media. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.