DALLAS–While hurricane intensity could likely increase as the Earth warms, the regions in which they form and possibly even the maximum number of storms per season could remain the same, a weather expert said here.

Robert Korty, assistant professor, department of atmospheric science at Texas A&M University, outlined for inland marine underwriters the conditions under which hurricanes form, and provided some insight into what could happen to hurricane activity as global warming conditions progress.

His comments were made during the Inland Marine Underwriters Association's 75th Annual Conference.

While hurricanes tend to form over water that is around 80 degrees Fahrenheit, Mr. Korty said that 80 degrees is not a “magic number.”

Hurricanes in the Atlantic and identical tropical cyclones in other parts of the world have formed in their respective areas throughout history, during which time the Earth has gone through various heating and cooling cycles, he explained.

If there was something special about the number 80, Mr. Korty said, then hurricanes would begin to form in water that currently averages 77 degrees if the Earth warmed by an average of three degrees, yet that is not expected to happen.

Additionally, he said the number of tropical cyclones and hurricanes each year reaches between 90 and 100.

Scientists, Mr. Korty said, are unsure why exactly that is. “We don't know why there are any tropical storms at all, or why there are not 1,000 or 10,000. It's pretty close to 100 each year, and what controls that is something that we are working really hard to figure out.”

Storm intensity, though, Mr. Korty said, will likely increase as the Earth warms. But he noted that certain factors regarding the Earth have and will prevent hurricanes from reaching speeds far in excess of what the maximum is today, which is about winds of 180-to-200 miles per hour.

For example, Mr. Korty said, wind shear limits how intense a storm gets, and hurricanes expend much of their energy “restoring symmetry” with their surroundings.

Additionally, he said the ocean gets “very cold, very fast” at a depth of about 200 feet. Basically, as hurricanes stir up the waters, warmer water necessary for fueling hurricanes mixes with the cooler, deeper water, and that limits hurricane intensity.

What can be expected is that as the Earth warms, it is likely that more of the hurricanes that do form will reach maximum intensity.

Mr. Korty stressed that knowledge about hurricanes is limited, and he said that information used in making assumptions about hurricane behavior should be looked at over very long periods of time.

For example, he cast some doubt on the concept of the multidecadal signal, which refers to the belief among some atmospheric scientists that hurricane activity in the Atlantic ebbs and flows according to 15- to 20-year cycles.

This theory is based on the fact that Atlantic hurricane activity was more active in the 1950s and '60s, less active in the '70s and '80s, and more active in the '90s through today, he related.

But Mr. Korty said the time period used to make this assumption is far too short to say with any degree of certainty that there is a pattern or cycle.

He likened this thinking to weather patterns from the 1940s to the 1970s, when the degree of global warming reached a plateau and some scientists believed the Earth was heading toward another ice age. If looked at over a longer period of time, however, Mr. Korty noted that it is clear the Earth is warming, rather than cooling. It is helpful, he said, to “keep the long term in perspective.”

Special Reports /

Storm Count Could Stay Even Despite Global Warming

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