|MadSci Network: Earth Sciences|
Hi Barry - Thanks very much for writing to Mad Scientist Network. You have asked an important question that many climate scientists have been working very hard on. The answer to your question is that it is impossible to say whether or not any individual hurricane (like Katrina) or snow storm or drought is caused by global warming. Weather events like these depend on many other factors as well as temperature. All we can talk about is if the chance a hurricane is formed, or its strength, may be larger because of higher temperatures from global warming. We can figure this out if we look at the physics of how hurricanes form. Hurricanes form when the ocean is warm enough to evaporate large amounts of liquid water to gas. Once in the atmosphere the water eventually turns back into liquid to form clouds and rain, and warms the surrounding air as a result. As the air warms it expands, and creates a region of low pressure. This low pressure causes the winds to spiral and form a hurricane. So in general, the warmer the ocean surface is the more likely it is that a hurricane can form. Also, the warmer the ocean surface is the more likely it is that any hurricanes that do form are stronger. (For example, a category 4 or 5 compared to a category 2 or 3 hurricane.) But itís important to remember this just tells us what is likely due to basic scientific principles. This can not tell us what actually happened on any day for any hurricane. Right now many scientists believe that historical data and computer models do NOT show that the number of hurricanes has increased significantly due to global warming. However, they do believe that on average hurricanes are getting stronger. So the chance of a hurricane hitting any place isnít higher, but those that do exist are likely to be more destructive than those in the past. I very much hope that you do not have another hurricane coming near your home. Stephanie
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