[extropy-chat] Hurricanes and global warming

[Hal Finney]

Mike Lorrey writes:
> Such claims are one more proof that the chicken littles are cherry
> picking the data. The facts are clear: the first half of the 20th
> century saw TWICE as many class IV and V hurricanes as the second half
> of the 20th, yet the chicken littles claim that most of the warming
> happened in the 2nd half of the century. If warming were the cause,
> then the late 20th should have had more severe hurricanes than the
> early 20th.

Actually if you look at http://www.nhc.noaa.gov/pastdec.shtml you can can
count 10 class IV and V hurricanes from 1900-1950 and 7 from 1950-2000,
which is not twice as many.

As the articles I linked to explain, the scientific consensus is that
global warming is not linked to hurricane frequency.  So if we respect
the scientific consensus, which I would advise, we will not be surprised
that there is no correlation with temperature.  Of course, if we believe
what science tells us, we will also accept that humans are making a
significant contribution to global warming, which may not be so palatable.

> There is a significant relationship between sunspot cycle intensity and
> incidence of severe hurricanes. The second half of the 20th century saw
> sunspot cycles peaking at a minimum of 120 to as many as 200, while the
> cycles prior to that period, going back to the 18th century, rarely
> exceeded 100. The latest cycle, which began in 1996 and which we are on
> the tail end of now (we will reach minimum in 2006) has only peaked at
> 120. The one exception in the 2nd half of the 20th was the 1966-76
> period which peaked at 110 and as I recall, people were talking about
> the next ice age at that point.

http://science.msfc.nasa.gov/ssl/pad/solar/images/zurich.gif shows a
graph of sunspot activity for the past 250 years.  I don't see that good
a fit to the hurricane numbers.  According to the hurricane table, the
decades with the most major hurricanes were the 10s, 30s, 40s and 50s.
The first three had relatively low solar activity, fitting your theory,
but the 50s saw the highest sunspot levels recorded on the chart, around
250, and the late 40s were high too, over 200.

> Why does this all matter, you ask? 
> Where is that flux going disproportionately, due to holes in the
> radiation belts at the poles? At the poles. The poles warm up more when
> the sun gets hotter, the equator doesn't warm up at all or much at all,
> so the thermal differential between the equator and the poles drops,
> and so the lesser energy differential means less severe storms.

This doesn't make sense.  While it's true that active sunspot cycles
correlate with a hotter sun, if the sun is hotter, the whole earth is
going to get hotter.  There's no reason the energy would go to the poles.
The only energy that might be preferentially deposited there would be
charged particles, but that is a small fraction of the energy from solar
infrared and visible radiation.  The auroras are pretty but they don't
make you sweat.

> So, what is the proper conclusion? If we are truly entering a period of
> more severe storms, then it can only be because the poles are entering
> a cooling period due to lower solar output. If we are entering a true
> Maunder Minimum, expect to see the next sunspot cycle, due to peak in
> 2010, to reach a VERY low peak of between 70-100. Winters will get more
> severe, and we'll see more snowy blizzards at lower latitudes in the
> states. The Gulf Stream will speed up again, and Northern Europe will
> get socked in with a nicely temperate fog like it once was.

I don't see any reason to expect this.  Looking at the sunspot chart,
the last peak was a little lower the the previous two, but the one before
those had been an even bigger drop.  There is quite a bit of fluctuation
from cycle to cycle, but nothing in the pattern strongly suggests that
the next few cycles will be extremely low.

Hal