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experts comment on Hurricane Gustav

The hurricane hit large parts of the Louisiana coast but did not reach the levels of intensity of Hurricane Katrina, which devastated New Orleans three years ago.

Jane Strachan, Willis Research Fellow, Walker Institute for Climate Change, Department of Meteorology, University of Reading, said:

“As Hurricane Gustav approaches the coast of USA, with severe impacts expected in New Orleans almost exactly three years since Hurricane Katrina struck, we cannot help but start to question whether this is normal climate behaviour.

“It is impossible for climate scientists to look at a particular tropical cyclone and say whether it is due to climate change or not. This is not how climate analysis works. Climate is average weather, and therefore to assess climate activity and how the climate varies, climate scientists must look at the statistics of average activity over a period of time. So, is global warming changing the frequency of tropical storms? Where they are making landfall? How intense the impacts of the storm will be?

“To understand how global warming may be changing tropical cyclone activity, scientists are looking very carefully at the atmospheric and oceanic conditions that lead to the formation, the structure and the motion of these complex tropical features. Based on this work, there is much active research going on into tropical cyclones and how their behaviour may be changing. However, the global climate system is incredibly complex and tropical cyclones have a very delicate interaction with the background climate conditions. It is true that scientists are still trying to unravel how this complex relationship may be changing. Not only with global warming, but also with natural climate variability, such as the relationship between tropical cyclones and El Niño.

“Scientists are using a combination of past storm data, state of the art climate models, and physical understanding to try and solve this puzzle, and we are starting to get some answers. But, while scientists are trying to solve this incredibly complex puzzle, it is inevitable that contradicting findings will emerge. This doesn’t reveal that scientists don’t agree or don’t know what they are talking about. It just reflects the huge complexity of the science of tropical cyclones.

“In terms of impacts, we also need to look at our own behaviour- a tropical cyclone only becomes a disaster when humans become involved. If we build oil platforms in the Gulf of Mexico, if we insist on developing Miami beach, if we continue living in New Orleans, we are increasing the risk and it is inevitable that the impact of tropical cyclones will increase. More money will be lost, and more people will suffer.”

Bob Ward, Director of Public Policy at Risk Management Solutions, who co-ordinated a review of the methods used by the United States Army Corps of Engineers to assess the risk of flooding in New Orleans, said:

“New Orleans is better prepared to withstand the effects of Hurricane Gustav than it was three years ago when it was struck by Hurricane Katrina. The Army Corps of Engineers has carried out work on 236 of the 325 miles of floodwalls and levees protecting the city. However, only about a quarter of the work to protect the city against a storm that happens on average once every hundred years has been completed. The ambitious plan is scheduled to finish in 2011.

“The extent of any damage caused by the storm surge from Hurricane Gustav will depend on a number of factors, like where it reaches land and its strength. The National Hurricane Center is currently predicting that it will be a weak category 3 hurricane with sustained winds of 115 miles per hour. The Center is predicting that there is only a 40% chance of the storm surge to the east of New Orleans reaching 10 feet above normal levels. By comparison, Hurricane Katrina was a category 5 storm just hours before it reached land, with winds of 170 miles per hour, and generated a surge of 20 feet in New Orleans.

“Hurricane Gustav may cause some overtopping of the flood defences in certain parts of New Orleans, putting them under pressure. However, it is unlikely that flooding will occur on the scale caused by Hurricane Katrina.”

Bill McGuire, Director of the Benfield UCL Hazard Research Centre, said:

“There is growing evidence that higher sea-surface temperatures resulting from climate change have driven increased Atlantic hurricane activity in the last few decades. Given this scenario, the locations of a number of major US cities in the hurricane belt, in particular New Orleans, Miami and Houston, are becoming increasingly precarious.”

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