US Hurricane Expert Stirs Global Warming Debate
Author: Jim Loney
In an article published in the journal Science, Chris Landsea, a leading researcher at the US National Hurricane Center, challenged studies that found a dramatic jump in hurricane intensity in recent years.
The paper is the latest salvo in the debate among climate scientists on whether human-induced global warming is producing stronger hurricanes.
The argument reached boiling point during last year's record-shattering Atlantic hurricane season, which produced 28 tropical storms and hurricanes including, for the first time in a single season, four of the most destructive Category 5s.
Because of improvements in technology, including more and better satellites, forecasters now produce more accurate estimates of a storm's power, which could mean more hurricanes are now recognized as powerful Category 4 and 5 storms, Landsea said.
"It's a consequence of us better monitoring things the last 15 years than we did back in the '70s and '80s," Landsea said.
Some climate scientists argue that global warming is causing more intense hurricanes, which draw their energy from warm sea water. Sea surface temperatures have increased by about 1 degree Fahrenheit (0.55 Celsius) in the last three decades, they say.
Last year, respected researcher Kerry Emanuel of the Massachusetts Institute of Technology wrote in Nature magazine that the energy dissipated by hurricanes in the North Atlantic has doubled in the last 30 years.
Another study, by Georgia Institute of Technology researchers and published in Science, found the proportion of hurricanes reaching Category 4 and 5 has nearly doubled in the last 35 years.
Landsea is among a group of scientists who say the impact of global warming on hurricanes is not clear, and the studies do not account for inaccurate information in storm databases.
"It's not to say that global warming isn't causing changes. I don't dispute the fact that global warming is going on or that it can have an impact on hurricanes," Landsea said.
Landsea said researchers had data from only two geostationary satellites to monitor storms in 1975. Now, much better pictures are available from eight satellites.
Today's scientists can get readings on hurricanes around the clock, where only daylight images were available decades ago.
Together, the technology changes mean forecasters are more likely than in the past to determine that a hurricane has higher winds.
"The hurricane doesn't change. But you're getting a better analysis of how strong that hurricane is," Landsea said.
The Science article said reanalysis of historic data has found about 70 previously unrecognized Category 4 and 5 hurricanes in the eastern hemisphere from 1978 to 1990. Such a finding would weaken the argument that the number of intense hurricanes is rising.
"For some of the storms in the north Indian Ocean, if they were to occur today, we would say they are Category 4 or 5 and yet they are listed in the data as Category 3 or weaker," Landsea said.
A cyclone that hit Bangladesh in 1970 and killed up to 500,000 people is not even listed as a hurricane, he said.