It is unfortunate, but nevertheless the case, that one has to regard papers on climate change with extra scrutiny due to the existence of a political lobby determined to "prove" that anthropogenic climate change is either non-existent or not a problem. Therefore papers that confirm the politically convenient view start off under a cloud of suspicion, whether the science is, in fact, either good or bad.
I have had a quick look at the paper referred to below, which seems to rely heavily on other papers cited with which I am not familiar - and not being a meteorologist or climatologist I needs must proceed with caution.
However, a couple of points strike me, and I raise them here in the hope that more expert people than I may comment.
Firstly, although looking at past records of cyclones back to 1900 may show the degree of fluctuation in rates from decade to decade, it would never be expected that a trend could be seen that could inform speculation about future rates if future rates are affected by very recent climate change. Phrases such as "with no trend identified in various metrics of hurricane damage over the 20th century" are therefore unhelpful and possibly misleading.
To inform speculation as to whether future rates of intense cyclones may increase, evidently one needs an approach based on judgement from projected increases in sea temperature, which appear to be indisputable.
The paper quotes some other studies that model a projected increase in wind speed in a cyclone of only a few percent, given a rise in sea temperature of a few degrees, and anyone can appreciate that if you have a cyclone with wind speeds of 100 mph, it won't be that much worse if they increase to 105 mph.
What seems to me to be more to the point is a consideration of what factors cause a storm to develop into a class 5 rather than a class 1. From what I understand about Katrina, its intensity developed partly as a result of warm sea temperatures, but more because of special atmospheric conditions.
Now, suppose one could formulate the conditions for a class 5 cyclone as follows:
Need factor A - probability of A is 10%
Need factor B - probability of B is 30%
Then the overall probability is 3%. But if B is "sea temperature greater than X", once global sea temperatures increase, the probability of B also increases, and the overall probability of a class 5 may go from 3% to 10%. In this case it would be possible to show the expected increase in frequency of very intense cyclones, which would be more meaningful than modelling the increase in wind speed in one cyclone, given an increase in sea temperature in isolation to other factors.
Does this make sense?
Roger Musson
> -----Original Message-----
> From: Natural hazards and disasters
> [mailto:[log in to unmask]]On Behalf Of Peiser,
> Benny
> Sent: 31 August 2005 12:38
> To: [log in to unmask]
> Subject: HURRICANES AND GLOBAL WARMING
>
>
> Bulletin of the American Meteorological Society (in press)
> http://sciencepolicy.colorado.edu/admin/publication_files/reso
> urse-1766-2005.36.pdf
>
> Hurricanes and Global Warming
> Pielke, Jr., R. A., C. Landsea, M. Mayfield, J. Laver and R.
> Pasch, in press, 2005.
> December. Hurricanes and global warming, Bulletin of the
> American Meteorological
> Society.
>
> Abstract
> This paper reviews recent research on tropical cyclones and
> climate change from the
> perspective of event risk - the physical behavior of storms,
> vulnerability - the
> characteristics of a system that create the potential for
> impacts, but independent of event
> risk, and also outcome risk - the integration of
> considerations of vulnerability with event
> risk to characterize an event that causes losses. The paper
> concludes that with no trend
> identified in various metrics of hurricane damage over the
> 20th century, it is exceedingly
> unlikely that scientists will identify large changes in
> historical storm behavior that have
> significant societal implications, though scientists may
> identify discernible changes in
> storm behavior. Looking to the future, until scientists
> conclude (a) that there will be
> changes to storms that are significantly larger than observed
> in the past, (b) that such
> changes are correlated to measures of societal impact, and
> (c) that the effects of such
> changes are significant in the context of inexorable growth
> in population and property at
> risk, then it is reasonable to conclude that the significance
> of any connection of humancaused
> climate change to hurricane impacts necessarily has been and
> will continue to be
> exceedingly small.
>
> Hurricanes and Global Warming
>
> Debate over climate change frequently conflates issues of
> science and politics.
> Because of their significant and visceral impacts, discussion
> of extreme events is a
> frequent locus of such conflation. Linda Mearns, of the
> National Center for Atmospheric
> Research (NCAR), aptly characterizes this context, "There's a
> push on climatologists to
> say something about extremes, because they are so important.
> But that can be very
> dangerous if we really don't know the answer" (Henson, 2005).
> In this essay we focus
> on a particular type of extreme event, the tropical cyclone
> in the context of global
> warming (tropical cyclones are better known in the United
> States as hurricanes, i.e.,
> tropical cyclones that form in the waters of the Atlantic and
> Eastern Pacific oceans with
> maximum 1-min average surface winds that exceed 32 m/sec).
>
> In our discussion we follow distinctions between event risk
> and outcome risk
> presented by Sarewitz et al. 2003. "Event risk" refers to the
> occurrence of a particular
> phenomenon and in the context of hurricanes we focus on
> trends and projections of storm
> frequencies and intensities. "Vulnerability" refers to "the
> inherent characteristics of a
> system that create the potential for harm" but which are
> independent from event risk. In
> the context of the economic impacts of tropical cyclones
> vulnerability has been
> characterized in terms of trends in population and wealth
> that set the stage for storms to
> cause damage. "Outcome risk" integrates considerations of
> vulnerability with event risk
> to characterize an event that causes losses. An example of
> outcome risk is the potential
> for a $100 billion hurricane in the United States. To
> calculate such a probability requires
> consideration of both vulnerability and event risk. This
> essay discusses hurricanes and
> global warming from both of these perspectives.
>
> FULL PAPER at:
> http://sciencepolicy.colorado.edu/admin/publication_files/reso
urse-1766-2005.36.pdf
© Copyright 2005 American Meteorological Society (AMS)
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