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Did Global Warming Cause Katrina? |
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Did global warning cause Katrina?
The answer is more subtle than what the experts are saying. There are three related questions and for simplicity, they seem to roll all three answers into one. Here are the relevant questions and the right answers.
Q1. Did global warming cause Katrina or significantly affect its intensity? (Yes.)
Q2. Has global warming increased damage due to hurricanes? (No.)
Q3. Should we judge global warming's impact on hurricanes as negligible? (No.)
Answers to Q1 and Q2 seem to contradict, and that is why the experts answer Q1 incorrectly as "No". They are afraid that if they said "yes" (the correct answer) to Q1 we would think the answer to Q2 is "yes", which it is not.
The basic idea is this. Weather is chaotic, which means a small change at one point in time has a progressively larger effect on all the particulars of weather as time goes on. This is often called the "butterfly effect." A butterfly flaps its wings and causes a tornado at some later date. If global warming has had even 1/5 of its theoretical effect, that still amounts to the energy of 1 hurricane a year world wide. That's an unthinkably bigger disturbance to global weather than a butterfly, and there can be no doubt that over the last few decades such a large continuing disturbance to the global weather system has rearranged all the particulars.
The path of every present hurricane has been changed, new ones have been brought into existence, and ones that would have existed (without global warming) never happened. Such is the sensitivity of chaotic systems, that we can be virtually certain Katrina would not have struck New Oreans had there been no global warming.
What we cannot tell is whether hurricane damage would have been more or less over the last five years. No one will ever know what hurricanes would have struck the U.S., where they would have struck, or how much damage they would have caused without global warming.
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Rethinking Warming and Hurricanes For decades, Kerry Emanuel, the meteorologist and hurricane specialist from the Massachusetts Institute of Technology, asserted that no firm link had been established between warming and the intensity and frequency of hurricanes.
But in August, two weeks before Hurricane Katrina struck the Gulf Coast, Professor Emanuel wrote in the journal Nature that he had discovered statistical evidence that hurricanes were indeed affected by global warming. He linked the increased intensity of storms to the heating of the oceans.
"I predicted years ago that if you warmed the tropical oceans by a degree Centigrade, you should see something on the order of a 5 percent increase in the wind speed during hurricanes. We've seen a larger increase, more like 10 percent, for an ocean temperature increase of only one-half degree Centigrade."
''His paper has had a fantastic impact on the policy debate,'' said Stephen Schneider, a climatologist at Stanford. ''Emanuel's this conservative, apolitical guy, and he's saying, 'Global warming is real.' '' Interview with Dr Emanuel
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Can we show statistically that there has been increased damage from hurricanes as a result of global warming?
Not yet and not for a long time to come. That's because hurricane damage is just too unpredictable. A very few storms account for most of the damage. It's like trying to call an election by polling one person every three years. Even if we were headed for a 60/40 landslide it would take decades to prove it. But the fact that we can't prove it from damage statistics just means our statistics are poor, it doesn't mean the extra damage is not significant.
If we can't tell from damage statistics, how can we tell?
About 99.8% of hurricane data is for hurricanes that are not in contact with the U.S. By studying all hurricane data, we can tell if their numbers are increasing. If there are more category 4 and 5 hurricanes wandering the oceans, more are sure to hit land at the wrong place over the long run. If the danger of the hurricane population goes up 20%, you can't say there will be 20% more damage in the next 10 years, that's a matter of luck. But you can say that our best guess is 20% more damage. This type of estimation is exactly the type of information insurance companies base their cost of coverage on. Just because they don't know what will actually happen doesn't mean they assume it will be zero. They play the odds and your insurance premium goes up.
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http://zfacts.com/p/240.html | 01/18/12 07:18 GMT
Modified: Thu, 03 Apr 2008 20:27:53 GMT
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