Off by 6 Orders of Magnitude

May 22nd, 2006

Posted by: Roger Pielke, Jr.

In an ABC News story on changing hurricane intensities NCAR scientist Greg Holland asserts,

“Remember, for each 10 mph increase of wind speed,” says atmosphere scientist Greg Holland, “there’s about 10 times more damage, and 20 times more financial loss.”

There are those who argue that damage is proportional to the sqaure or even the cube of changes in wind speed, but no one I am aware of who argues that there is a factor of 10 or 20 per 10 mph. This would equate to a difference of 10^8 or 10,000,000 times more damage beween a category 1 and a category 5 (i.e. from 75 mph to 155 mph).

Empircally, when we look at normalized hurricane damage over the past 106 years, we find about 100 times more damage in category 4/5 storms than category 1.

6 Responses to “Off by 6 Orders of Magnitude”

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  1. Steve Lyons Says:
    May 23rd, 2006 at 6:10 am

    I would have to agree with Dr. Pielke. What is likely also more important to note is that most structures are build to “possibly” withstand 100-120 mph winds, but very few “homes” can withstand 160 mph CAT 5 winds. I have been in a wind tunnel at 160 mph and cannot imagine many homes standing up to sustained winds this fast, not to mention higher gusts atop these sustained winds. And this is the lowest of CAT 5 wind speeds. I do not think it necessary to add another category, the unlimited upper bound to CAT 5 already covers the strongest TC’s, which are (fortunately) extremely rare at landfall!

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  2. Roger Pielke, Jr. Says:
    May 23rd, 2006 at 6:40 am

    Greg Holland writes to a list-serv that he was misquoted by ABC:

    “If you view the original video, you will see that I said a doubling of the winds leads to a 10 times increase in damage….I have written to the ABC to have this corrected.”

    Here is the original video:

    http://abcnews.go.com/Video/playerIndex?id=1989535

    Readers/viewers can evaluate for themselves.

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  3. Roger Pielke, Jr. Says:
    May 23rd, 2006 at 7:04 am

    Further details — Greg says that there is a longer video to be aired in the future with his quotes not present in the shorter version. I accept that ABC misquoted him.

    Still, I suggested that he correct the numbers. A doubling of wind speeds will lead to an increase in damage of about 4 to 8 times, not 10, and certainly not 20 times the financial impacts.

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  4. Roger Pielke, Jr. Says:
    May 23rd, 2006 at 8:07 am

    Further, and perhaps final, update:

    Greg writes me to note that ABC News has revised the news story to remove the quote altogether:

    http://abcnews.go.com/GMA/Science/story?id=1986862&page=1

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  5. Steve Bloom Says:
    May 23rd, 2006 at 1:44 pm

    My comment from yesterday, lost apparently because of a snafu with the shift to Typekey, was to the effect that a phone call to Greg Holland before putting up this post would have been the polite thing to do.

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  6. Roger Pielke Jr. Says:
    May 23rd, 2006 at 1:52 pm

    Steve-

    Thanks. Greg and I have been in constant email contact on this, and his comments in the ABC article have been the subject of a lengthy exchange on the TS list-serv the past 24 hours (on damage functions as well as several other subjects).

    Given that my post helped to correct a major error by ABC on Greg’s comments, which he was unaware of, I think that this shows the value of a blog discussion providing an immediate critique of a media story.

    And BTW, despite the error, which happens to all of us from time-to-time of course, kudos to ABC for their quick action to correct the mistake on their WWW site.

    FYI, we will soon be publishing data on damage functions as related to different hurricane intensity levels.

    Thanks.