GLOBAL WARMING Experts dispute weather trends

One links global warming and hurricane intensity. Another sees no such trend.
SOUTH FLORIDA SUN-SENTINEL
ORLANDO, Fla. -- Is global warming to blame for the past two horrific hurricane seasons?
Yes, says Judith Curry, a professor of atmospheric sciences at the Georgia Institute of Technology. Her argument: Worldwide sea surface temperatures have increased by about 1 degree since 1970, resulting in about 50 percent more tropical storm activity than normal.
No, counters Jim O'Brien, a professor of meteorology and oceanography at Florida State University. His point: Since 1850, the Earth has undergone numerous warming and cooling cycles and there has been no distinct trend in the overall intensity of hurricane seasons.
The debate by the two climate experts at Friday's National Hurricane Conference took on added importance in light of the past season that produced a record 28 storms and 15 hurricanes.
Curry said greenhouse warming, created by the trapping of gases in the atmosphere, has resulted in a sharp increase in tropical activity, particularly in the past decade. Since 1995, 166 tropical storms, including 112 hurricanes, 28 of them Category 4 and 5 systems, have been spawned in the abnormally warm waters of the Atlantic basin.
What's cited
Although scientists say a natural cycle of ocean warming is responsible for that rise in activity, Curry noted that the peak period of the previous cycle, from 1945 to 1955, saw considerably fewer systems: 115 tropical storms, including 74 hurricanes, 19 of them Category 4 and 5.
As a result of global warming, hurricane seasons now are five days longer on average than they were 100 years ago, Curry said.
In addition, the United States has suffered a "precipitous increase" in hurricane strikes in just the past 10 years.
"We see an overall trend," she said. "This implies some external force is raising sea surface temperatures in tropical regions."
Ocean temperature
O'Brien disputed that the world's oceans have increased in average temperature, including in the most active tropical months, August through October.
He said to determine if the seas have actually warmed, readings would have to be taken as deep as 1,000 feet worldwide.
"There's no obvious warming," he said.
O'Brien said contrary to press reports, extraordinarily warm Gulf of Mexico waters did not supercharge Hurricane Katrina, which devastated New Orleans and the Gulf Coast of Mississippi last August.
Instead, he said, the normally hot water near the shoreline did.
"In my view, it was just August," he said. "Go put your toe in the Gulf of Mexico; it's hot."
O'Brien said warm periods in the Atlantic have historically produced powerful hurricanes, and storm intensity is further influenced by El Ni & ntilde;o or La Ni & ntilde;a conditions -- the warming and cooling cycles in the eastern Pacific.
He also showed a graphic of all hurricanes and their strengths since the mid-1800s, depicting a chaotic jumble.
"If you see a trend, please raise your hand," he said.