[extropy-chat] FWD [PvT] Re: Hurricanes and global warming

[Terry W. Colvin]

There is no doubt that we are in a period of elevated activity now (began
in 1995) and that such periods have lasted decades. This cycle seems tied
to some sort of coupled air-sea decadal oscillation. The only one we have
sure knowledge about right now is the Pacific Decadal Oscillation (PDO) but
we don't know enough about it to make any connection with hurricane
activity cycles though it is true that the PDO was negative in the period
of previous high activity and positive from the early 60's into the mid
90's and is negative now. In its positive phase, the PDO mimics the El Niño
and also enhances Niños while suppressing Niñas and the opposite is true
during negative phases. Niños, of course inhibit hurricane formation in the
ATL while enhancing EPAC activity. 

With regard to the Solar activity. What we think of as an 11 year sunspot
cycle is really a 22 year magnetic cycle with two activity maxima. There
are other cycles of activity at work including a 180 day one and one about
200 years in length (prior to 1957, 1780 had the highest annual sunspot
count average. However, these other cycles are not multiples of the 22 year
one so the various cycles get out of phase and interfere with each other
and over long periods of time we end up with things like the Maunder and
Spörer Minima in the 17th and 18th Centuries. It's these longer term cycles
that are most important in the Solar-Climate Connection.

Steve


-- 
"Only a zit on the wart on the heinie of progress." Copyright 1992, Frank Rice


Terry W. Colvin, Sierra Vista, Arizona (USA) < fortean1 at mindspring.com >
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