Re: Hurricane Intensity: An Example of Global Warming Alarmism

Friends: Here are some of my perhaps uninformed musings. I am a self-acknowledged climate-change novice, although I tend to be much more impressed by the empirical evidence in support of the global warming hypothesis than some others contributing to this list. Although I tend to agree that one season of extraordinarily active and strong hurricanes does not prove global warming, I think all will agree that it does not invalidate it either; in fact such activity is more or less consistent with model predictions.
I also think that the conclusion that a 0.5 deg C average global ocean surface warming is not sufficient to stimulate such storm activity may be suspect. Could it not be that ocean surface temperatures in the equatorial latitudes may be warming more than the global average? ( I don't know what the measurements show if there are any). And might not this be more severe in the region of the south Atlantic/Carribean? If the thermalhaline circulation, which carries warm water northward away from the equator, is actually slowing down, would not this result in increasing average surface temperatures at equatorial latitudes (and decreasing surface temperatures in the higher latitudes) just in the region where we are seeing increased storm action and intensity?
I believe that one of the factors that plays a significant role in hurricane intensity is the amount of water vapor in the air. This, in turn, must be at least partially dependent on the vapor pressure of the ocean water underneath the storm center which in turn is dependent on the surface ocean temperature. It seems to me worth noting that in the temperature regime of summer surface ocean in the equatorial regions the vapor pressure of water increases at a rate of about 6% per deg C. So it would not take a large increase in the summer surface ocean temperature to cause a significant increase in surface water vapor pressure and therefore more water vapor in the atmosphere. And all this could add up to support greater storm frequency and intensity.
I would very much like to learn more about this so if all of this is wrong please correct me.
Respectfully,
Ken Piers

Ken Piers

"We are by nature creatures of faith, as perhaps all creatures are; we live by counting on things that cannot be proved. As creatures of faith, we must choose either to be religious or superstitious, to believe in things that cannot be proved or to believe in things that can be disproved."
Wendell Berry

>>> "Rich Blinne" <rich.blinne@gmail.com> 4/26/2006 11:29 AM >>>
Recently, I have given examples of why I believe global warming is real. I
now want to give an example where I believe the case is oversold. The (less
famous) :-) Dr. Gray from Colorado State cogently explains why global
warming does not explain current hurricane intensities. There have been a
flurry of papers that conclude the other way recently nevertheless Dr. Gray
is holding his own. We shall see who prevails as the research continues.

http://hurricane.atmos.colostate.edu/Forecasts/2005/dec2005/

> There is no physical basis for assuming that global hurricane intensity or
> frequency is necessarily related to global mean surface temperature changes
> of less than ± 0.5oC. As the ocean surface warms, so too does global
> upper air temperatures to maintain conditionally unstable lapse-rates and
> global rainfall rates at their required values. Seasonal and monthly
> variations of sea surface temperature (SST) within individual storm basins
> show only very low correlations with monthly, seasonal, and yearly
> variations of hurricane activity. Other factors such as tropospheric
> vertical wind shear, surface pressure, low level vorticity, mid-level
> moisture, etc. play more dominant roles in explaining hurricane variability
> than do surface temperatures. Although there has been a general global
> warming over the last 30 years and particularly over the last 10 years, the
> SST increases in the individual tropical cyclone basins have been smaller
> (about half) and, according to the observations, have not brought about any
> significant increases in global major tropical cyclones except for the
> Atlantic which as has been discussed, has multi-decadal oscillations driven
> primarily by changes in Atlantic salinity. No credible observational
> evidence is available or likely will be available in the next few decades
> which will be able to directly associate global surface temperature change
> to changes in global hurricane frequency and intensity.
>

Some comments from the peanut gallery. Note that Dr. Gray admits that global
warming is real. He notes what I mentioned previously that global warming is
far less pronounced in the tropics than the poles such that the
SST increases in the tropical basins are half of the overall average. If
there was more warming in the basins then it would be a more significant
effect. For now, it's swamped by other factors. The other thing to note is
the discussion of thermohaline circulation as the primary driver of
hurricanes. Recall my previous post, ice cap melting makes this less
pronounced. This means that global warming produces two countervailing
effects on hurricanes. Just like global warming might produce a slightly
cooler Europe because of a less pronounced Gulf Stream (this is nowhere near
the "Day after Tomorrow" scenario), it is altogether possible that global
warming may actually produced SMALLER HURRICANES! So much for the alarmists.

Dr. Gray appears to be focusing on the effects of global warming and
hurricanes and focusing less on the yearly forecast. I look forward to
seeing his upcoming work.
Received on Wed Apr 26 14:40:36 2006