2007 hurricane season will be "very active" but not due to global warming
Rhett A. Butler, mongabay.com
April 3, 2007




Developing La Nina conditions, not global warming, should make the 2007 Atlantic hurricane season "very active," according to a top U.S. hurricane forecaster.

William Gray of the Department of Atmospheric Science at Colorado State University said he expects 17 named storms this year, including 9 hurricanes. He says there is a 74 percent chance that a category 3, 4, or 5 hurricane will hit the U.S. coastline (the historic average for the past century is 52 percent) and a 49 percent chance that such a storm would hit the Gulf Coast of the United States (versus an average of 30 percent for the past century).

"There were five hurricane seasons since 1949 with characteristics most similar to what we observe in February-March 2007 and characteristics that we expect to see in August-October 2007," wrote Gray and his colleagues Philip J. Klotzbach and William Thorson. "The best analog years that we could find for the 2007 hurricane season are 1952, 1964, 1966, 1995 and 2003. We anticipate that 2007 seasonal hurricane activity will have activity slightly more than what was experienced in the average of these five years. We expect the 2007 hurricane season to be very active."

Gray says that last year's forecasts, which predicted above average hurricane activity, were usurped by the weak to moderate El Niño event, a phenomenon that reduces Atlantic basin hurricanes. This year El Niño conditions have subsided, meaning that hurricane activity is likely to return.

He adds that the recent upswing in hurricanes is likely a result of naturally occurring multi-decadal Atlantic Ocean circulation variations, not global warming.


Warm ocean waters fuel hurricanes, and there was plenty of warm water for Katrina to build up strength once she crossed over Florida and moved into the Gulf of Mexico. This image depicts a 3-day average of actual sea surface temperatures (SSTs) for the Caribbean Sea and the Atlantic Ocean, from August 25-27, 2005. Every area in yellow, orange or red represents 82 degrees Fahrenheit or above. A hurricane needs SSTs at 82 degrees or warmer to strengthen. The data came from the Advanced Microwave Scanning Radiometer (AMSR-E) instrument on NASA's Aqua satellite. The GOES satellite provided the cloud data for this image. Image Credit: NASA/SVS.

"The Atlantic has seen a very large increase in major hurricanes during the 12-year period of 1995-2006 (average 3.9 per year) in comparison to the prior 25-year period of 1970-1994 (average 1.5 per year). This large increase in Atlantic major hurricanes is primarily a result of the multi-decadal increase in the Atlantic Ocean thermohaline circulation (THC) that is not directly related to global temperature increase or to human-induced greenhouse gas increases. Changes in ocean salinity are believed to be the driving mechanism. These multi-decadal changes have also been termed the Atlantic Multidecadal Oscillation (AMO)."

Gray notes that hurricane activity in the past 12 years appears to be similar to that of the 1940s and 1950s.

"There have been similar past periods (1940s-1950s) when the Atlantic was just as active as in recent years. For instance, when we compare Atlantic basin hurricane numbers over the 15-year period (1990-2004) with an earlier 15-year period (1950-1964), we see no difference in hurricane frequency or intensity even though the global surface temperatures were cooler and there was a general global cooling during 1950-1964 as compared with global warming during 1990-2004."

He says that the small changes is sea surface temperature recorded to date would not likely trigger an increase in the number of intensity of hurricanes.

"In a global warming or global cooling world, the atmosphere's upper air temperatures will warm or cool in unison with the sea surface temperatures," he continued. "We have no plausible physical reasons for believing that Atlantic hurricane frequency or intensity will change significantly if global ocean temperatures continue to rise. For instance, in the quarter-century period from 1945-1969 when the globe was undergoing a weak cooling trend, the Atlantic basin experienced 80 major (Cat 3-4-5) hurricanes and 201 major hurricane days. By contrast, in a similar 25-year period of 1970-1994 when the globe was undergoing a general warming trend, there were only 38 major hurricanes (48% as many) and 63 major hurricane days (31% as many) in the Atlantic basin. Atlantic sea-surface temperatures and hurricane activity do not necessarily follow global mean temperature trends."

Hurricanes require temperatures of around 27 degrees Celsius (81 degrees Fahrenheit) to develop. Some climate scientists have argued that because the Atlantic Ocean is cooler than other areas where hurricanes (known as typhoons in the Western Pacific and cyclones elsewhere) form, it is more susceptible to small changes in ocean temperature.

"The average conditions in the Atlantic at any given time are just on the cusp of what it takes for a hurricane to form. So it might be that imposing only a small (man-made) change in conditions, creates a much better chance of having a hurricane," said James Kossin, a research scientist at the University Wisconsin-Madison who led a hurricane study published earlier this year in Geophysical Research Letters. His work assessed two controversial studies (published in Nature and Science) that argued climate change is causing more frequent and intense hurricanes.

Related articles

Powerful hurricanes may be getting stronger due to warmer seas
(9/3/2008) Warming climate is causing the strongest hurricanes to strengthen and more moderate storms to stay the same, claims a new study published in Nature. However the data on which research is based is already facing fierce criticism.

Scientist forecast 4 Atlantic hurricanes in September
(9/2/2008) Prominent hurricane researchers are forecasting five tropical storms in the Atlantic for September, including four hurricanes. Two of these are expected to be "major" — category 3 or greater. Retired Colorado State University climatologist William Gray and Philip J. Klotzbach, who has taken over Gray's role as lead hurricane forecaster, estimate that Atlantic storms in September will be twice as active as normal.

Could hurricane Gustav be stopped or diverted?
(8/31/2008) With Gustav threatening to become the second major hurricane to hit New Orleans in three years, the question emerges, is there something that could be done to redirect or at least diminish storms from major population areas? In short, the answer is no, although someday there may be ways to reduce the intensity of these tropical storms. In the meantime, the best option is to avoid new construction in hurricane-prone regions.

69% of Floridians believe coast threatened by rising sea levels
(6/24/2008) 69 percent of Floridians believe that parts of the state's coasts may need to be abandoned due to rising sea levels over the next 50 years according to a new survey conducted by researchers at Yale University and the University of Miami.

2008 hurricane forecast: storm activity will be above normal
(5/22/2008) The U.S. government's weather agency predicts an above average Atlantic hurricane season this year.

Global warming will produce fewer hurricanes
(5/18/2008) Global warming will produce fewer Atlantic hurricanes, according to a study published today in the journal Nature Geoscience by a U.S. government meteorologist.

Massive deforestation of mangroves may have worsened scale of disaster in Burma
(5/13/2008) Weeks after the devastating cyclone Nagris struck Myanmar's Irrawaddy Delta on May 2nd, scientists and the media are debating the role in the scale of the disaster played by the region's deforestation of mangroves. According to recent studies, mangrove forests act as a buffer against the effect's of tropical storms like Nagris, though scientists don't yet fully understand the relationship between storm mitigation and mangroves.

Cyclone batters Madagascar
(2/22/2008) 29 people were reported dead after Cyclone Ivan, a category 3 storm, struck Madagascar. The storm flooded key rice-producing regions in the country and comes a month after Cyclone Fame killed 13 on the island.

Natural climate variations have larger effect on hurricanes than global warming
(12/12/2007) Natural climate variations, which tend to involve localized changes in sea surface temperature, may have a larger effect on hurricane activity than the more uniform patterns of global warming, a report in this week's Nature suggests.

Hurricane forecast calls for 7 hurricanes, 3 major, in 2008
(12/7/2007) Hurricane forecasters William Gray and Philip Klotzbach are predicting a "somewhat above-average" hurricane season for 2008. The Colorado State University researchers anticipate seven Atlantic hurricanes, three of them "major" (category 3 or higher), during the 2008 season. In total 13 named storms in the Atlantic are expected.

Historical records of Atlantic hurricanes are accurate says study
(11/28/2007) Counting tropical storms that occurred before the advent of aircraft and satellites relies on ships logs and hurricane landfalls, making many believe that the numbers of historic tropical storms in the Atlantic are seriously undercounted. However, a statistical model based on the climate factors that influence Atlantic tropical storm activity shows that the estimates currently used are only slightly below modeled numbers and indicate that the numbers of tropical storms in the recent past are increasing, according to researchers.

Hurricane Katrina released large amounts of carbon by destroying 320m trees
(11/15/2007) The destruction of 320 million large trees by Hurricane Katrina reduced the capacity of forests in the Southern United States to soak up carbon, reports a new study published in the journal Science. The research shows that hurricanes and other natural disturbances "can affect a landscape's potential as a 'carbon sink' because the dead vegetation then decays, returning carbon to the atmosphere, and because the old vegetation is replaced by smaller, younger plants."

Felix Death Toll Washes Up on Coastline
(9/7/2007) Nicaraguan and Honduran officials have announced that upwards of 100 people are confirmed dead, and another 120 still unaccounted for after Hurricane Felix made landfall earlier this week.

Felix: first time two Category-5 storms hit land in same season
(9/4/2007) Hurricane Felix made landfall in Nicaragua around 7:45 a.m. Eastern Time as a Category 5 storm with top winds at 160 mph (260 km/h), according to the U.S. National Hurricane Center.

Dean was 3rd most intense Atlantic hurricane at landfall
(8/21/2007) Hurricane Dean was the third most intense Atlantic hurricane to make landfall, according to forecasters at the National Hurricane Center who measured the storm's central atmospheric pressure.

Could a hurricane hit California?
(8/20/2007) San Diego has been hit by hurricanes in the past and could be affected by such storms in the future according to data from the National Oceanic and Atmospheric Administration (NOAA). While a hurricane in San Diego would likely produce significantly less damage than Hurricane Katrina in New Orleans, it could still exact a high cost to Southern California especially if the region was caught off guard.

U.S. government weather agency cuts hurricane outlook
(8/10/2007) The U.S. National Oceanic and Atmospheric Administration on Thursday reduced its forecast for the number of tropical storms and hurricanes expected during the 2007 Atlantic season. NOAA said it now expected between 13 and 16 named storms, with seven to nine becoming hurricanes and three to five of them classified as "major" hurricanes (categories 3, 4, or 5).

2007 hurricane season downgraded, questions over climate role remain
(8/6/2007) Hurricane researcher William Gray from Colorado State University cut his 2007 hurricane season outlook, saying there will likely be fewer storms than previously projected due to weak La Niña conditions and more atmospheric dust from Africa.

2007 hurricane season to be weaker than expected says forecaster
(7/24/2007) WSI Corp, a private forecaster, cut its 2007 hurricane season outlook, saying there will likely be fewer storms than previously projected, reports Reuters.

Hurricanes can help coral reefs
(7/17/2007) A close call with a hurricane can be beneficial to a stressed coral reef, reports a study published in Proceedings of the National Academy of Sciences (PNAS).





Comments?



News options Liquid error: Template not found languages/english/includes/x/_91.liquid



CITATION:
Rhett A. Butler, mongabay.com (April 03, 2007).

2007 hurricane season will be 'very active' but not due to global warming.

http://news.mongabay.com/2007/0403-hurricanes.html