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More Evidence Mann Is Wrong About Hurricanes

August 31, 2012

By Paul Homewood



In an interview a couple of weeks ago, Michael Mann told us

One of the more robust predictions is that in the Atlantic, hurricane intensities have increased and they will likely continue to increase, and so, it’s part of a trend, Katrina, the record season of 2005 was part of a trend towards more destructive storms.


There is plenty of evidence that there no such trend exists, but it is worth noting a paper published by Chris Landsea and Andrew Hagen earlier this year titled “On the Classification of Extreme Atlantic Hurricanes Utilizing Mid-Twentieth-Century Monitoring Capabilities”. The abstract states

An investigation is conducted to determine how improvements in observing capabilities and technology may have affected scientists’ ability to detect and monitor Saffir–Simpson Hurricane Wind Scale Category 5 hurricanes in the Atlantic Ocean basin during the mid-twentieth century. Previous studies state that there has been an increase in the number of intense hurricanes and attribute this increase to anthropogenic global warming. Other studies claim that the apparent increased hurricane activity is an artifact of better observational capabilities and improved technology for detecting these intense hurricanes. The present study focuses on the 10 most recent Category 5 hurricanes recorded in the Atlantic, from Hurricane Andrew (1992) through Hurricane Felix (2007). These 10 hurricanes are placed into the context of the technology available in the period of 1944–53, the first decade of aircraft reconnaissance. A methodology is created to determine how many of these 10 recent Category 5 hurricanes likely would have been recorded as Category 5 if they had occurred during this period using only the observations that likely would have been available with existing technology and observational networks. Late-1940s and early-1950s best-track intensities are determined for the entire lifetime of these 10 recent Category 5 hurricanes. It is found that likely only 2 of these 10—both Category 5 landfalling hurricanes—would have been recorded as Category 5 hurricanes if they had occurred during the late-1940s period. The results suggest that intensity estimates for extreme tropical cyclones prior to the satellite era are unreliable for trend and variability analysis.


Chris Landsea, of course, is one of the leading scientists at the National Hurricane Center, whilst Andrew Hagen is based at the Institute for Marine and Atmospheric Studies at the University of Miami, so it is reasonable to assume they know what they are talking about.

The paper includes a useful graphic showing how hurricane observation has changed over the years. It is clear that observation systems back in the 1940’s, although much better than even the 1930’s, were primitive by today’s standards.




There is also the following chart listing the ten Category 5 hurricanes they included in the study.




The authors make another interesting comment

“The analyses indicate that all of the hurricanes in the study that did not reach Category 5 strength would have been classified as a Category 4. The reader is reminded that the methodology employed is somewhat conservative. For example, many times during the late 1940s the aircraft often did not penetrate the center of hurricanes with central pressures in the 950s or even the 960s. If this criteria of, say, a 960-mb threshold were utilized, many of these cyclones would have been listed with a peak intensity of only Category 3 strength.”


To put these numbers into perspective, let’s look at the decadal summary of Category 5 Atlantic hurricanes (i.e. not just landfalls).


Decade Number of Category 5 Hurricanes Number As Adjusted By Landsea/Hagen
1921-30 2  
1931-40 5  
1941-50 1  
1951-60 4  
1961-70 6  
1971-80 3  
1981-90 3  
1991-00 2 2
2001-10 8 1


At 1940’s observation standards it would be reasonable to assume that the number of early 20thC hurricanes would have been greater. Similarly, from about 1960 onwards the number would probably be less. Nevertheless, it is clear that the number of Category 5’s in the last two decades is not high by historical standards. And not only Category 5’s, as the paper makes clear.

During recent years, there have been a number of Category 4 hurricanes that might have only been classified as weak hurricanes or even tropical storms if they had taken place at the same location during the late 1940s and early 1950s.

I find it highly unlikely Mann was unaware of any of this, but in that case why would he say something that was not true?

  1. Coldish permalink
    September 1, 2012 7:49 am

    It’s just more evidence that Mann exploits his position to pursue a non-scientific agenda, Thanks Paul, for your investigative work it’s much appreciated.

  2. Brian H permalink
    September 1, 2012 9:58 pm

    I assume the final question is ironic-rhetorical.

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