Hurricane intensity linked to global warming
August 15, 2006

A new study says climate change is affecting the intensity of Atlantic hurricanes and that hurricane damage will likely worsen in coming years due to increasing ocean temperatures. Unlike recent studies that have linked higher sea temperatures to an increase in the number of hurricanes, the new research shows a direct relationship between climate change and hurricane intensity.

In early August, forecasters at the National Ocean and Atmospheric Administration's National Hurricane Center revised downward slightly their early-season predictions of the 2006 Atlantic hurricane season. Citing atmospheric and oceanic conditions less conducive to hurricane formation than they initially expected, the center decreased its predictions of named storms (12-15 instead of 13-16), hurricanes (7-9 instead of 8-10), and major hurricanes (3-4 instead of 4-6). The revised prediction is still above-normal compared to the long-term average.

This pair of images from Japan's Advanced Microwave Scanning Radiometer for EOS Aqua satellite shows areas where sea surface temperatures were hurricane-ready on August 14, 2006 (top), and August 1 (bottom). Sea surface temperatures warmer than a threshold of about 28 degrees Celsius (about 82 degrees Fahrenheit) are one of the required ingredients for hurricanes to form. Areas where waters have reached the hurricane-ready threshold are yellow or red in these images, while areas where waters are generally to cool to support hurricanes are blue. Coastal areas where temperatures were not measured are light gray.

The study, published by James Elsner of Florida State University in the August 23 issue of Geophysical Research Letters, the journal of the American Geophysical Union, found that a correlation between average air temperatures during the June through November hurricane season and sea surface temperatures that help fuel hurricanes winds. Elsner says his work "helps provide verification of a linkage between atmospheric warming caused largely by greenhouse gases and the recent upswing in frequency and intensity of Atlantic hurricanes, including Katrina and Rita."

"The large increases in powerful hurricanes over the past several decades, together with the results presented here, certainly suggest cause for concern," he said. "These results have serious implications for life and property throughout the Caribbean, Mexico, and portions of the United States."

"I infer that future hurricane hazard mitigation efforts should reflect that hurricane damage will continue to increase, in part, due to greenhouse warming," Elsner said. "This research is important to the field of hurricane science by moving the debate away from trend analyses of hurricane counts and toward a physical mechanism that can account for the various observations."

Data questioned

Nevertheless, while Elsner's findings lend support to the contention that warmer temperatures will produce stronger hurricanes, they will not settle long-standing concerns among some scientists.

While several studies published since early 2005 have linked recent climate warming to the increasing occurrence and strength of hurricanes over the past thirty years, the research has proved controversial since some scientists say the system for tracking storms is flawed. They argue that storm data from 20 years ago is not nearly as accurate as current hurricane data making it nearly impossible to accurately compare storm frequency and strength over the period.

"Before aircraft and satellite monitoring were available, the Atlantic hurricane data are likely woefully underestimated - except where a hurricane ran directly over a ship or coastal community and there were meteorological observations of pressures and/or winds recorded," Chris Landsea, a scientist as the NOAA National Hurricane Center, told "Given that ship captains did their best to NOT sail into the eye of hurricanes, there is a very large underreporting bias in our databases during the late 19th and early 20th Centuries, except for hurricanes at landfall along populated coastlines. Disentangling trends due to bias in the hurricane dataset and possible global warming induced changes is then very problematic."

The new paper fails to steer around this controversy since it compares average global near-surface air temperature and Atlantic sea surface temperature with "hurricane intensities" from the National Oceanic and Atmospheric Administration's Atlantic basin hurricane database (HURDAT) over the past 50 years. Climate researchers are currently working to re-analyze existing tropical cyclone databases to address these concerns.

"What data we do have - and there certainly are biases in HURDAT that need to be addressed storm by storm - suggest that the middle of the 20th Century was about as busy as the last active 11 years have been (1995 to 2005)," Landsea added. "Disentangling trends due to bias in the hurricane dataset and possible global warming induced changes is then very problematic."


Global warming link to hurricanes challengedChris Landsea, a storm researcher at the National Hurricane Center, and colleagues argued in a paper published in the journal Science that improvements in technology now allow forecasters to produce more accurate estimates of a storm's power, meaning that more hurricanes are now recognized as Category 4 and 5 storms than prior to the 1980s. They said that the storm databases used by researchers who found links between hurricanes and warmer sea temperatures contain inaccurate information.

Hurricanes getting stronger due to global warming says study Late last month an atmospheric scientist at Massachusetts Institute of Technology released a study in Nature that found hurricanes have grown significantly more powerful and destructive over the past three decades. Kerry Emanuel, the author of the study, warns that since hurricanes depend on warm water to form and build, global climate change might increase the effect of hurricanes still further in coming years.

Birthplace of hurricanes heating up say NOAA scientists The region of the tropical Atlantic where many hurricanes originate has warmed by several tenths of a degree Celsius over the 20th century, and new climate model simulations suggest that human activity, such as increasing greenhouse gas emissions into the atmosphere, may contribute significantly to this warming. This new finding is one of several conclusions reported in a study by scientists at the NOAA Geophysical Fluid Dynamics Laboratory in Princeton, N.J., published today in the Journal of Climate.

Global Warming Fueled Record 2005 Hurricane Season Conclude Scientists Global warming accounted for around half of the extra hurricane-fueling warmth in the waters of the tropical North Atlantic in 2005, while natural cycles were only a minor factor, according to a new analysis by Kevin Trenberth and Dennis Shea of the National Center for Atmospheric Research (NCAR). The study will appear in the June 27 issue of Geophysical Research Letters, published by the American Geophysical Union.

US denies hurricane link with climate change Harlan Watson, chief climate control negotiator for the U.S. State Department, told the Associated Press that the Bush administration does not blame global warming or climate change for extreme weather -- including the hurricanes that thrashed the Gulf earlier this year.

Hurricane Katrina damage just a dose of what's to come The kind of devastation seen on the Gulf Coast from Hurricane Katrina may be a small taste of what is to come if emissions of the greenhouse gas carbon dioxide (CO2 ) are not diminished soon, warns Dr. Ken Caldeira of the Carnegie Institution's Department of Global Ecology in his opening remarks at the 7th International Carbon Dioxide Conference in Boulder, Colorado, September 26, 2005.

Hurricane could hit San Diego San Diego has been hit by hurricanes in the past and may 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.

Fewer hurricanes predicted for 2006 season William Gray and Philip Klotzbach of the Colorado State University hurricane forecast team issued a report today reducing the number of storms expected to form in the Atlantic basin this season. However, the researchers still call for above-average hurricane activity this year and expect above-average tropical cyclone activity in August and September. That's despite an average start to the season with two named tropical storms forming in June and July.

2006: Expect another big hurricane year says NOAA The 2006 hurricane season in the north Atlantic region is likely to again be very active, although less so than 2005 when a record-setting 15 hurricanes occurred, according to the National Oceanic and Atmospheric Administration (NOAA).

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CITATION: (August 15, 2006).

Hurricane intensity linked to global warming.