From: jgacker@news.gsfc.nasa.gov (James G. Acker)
Subject: Re: Alaska to shoot hundreds of wolves/ Milankovitch Cycle
Organization: Goddard Space Flight Center
X-Newsreader: TIN [version 1.1 PL6]
Date: Mon, 23 Nov 1992 21:09:11 GMT

cvakgaaq@vmsb.is.csupomona.edu wrote:

: 	Milankovitch was a Serbian mathematician who showed that because the
Earth's orbit is elleptical and the Earth has an Axial tilt, and wobbles about
: the axis, then there are variations over periods of thousands of years in the
: amount of solar radiation striking the Earth's surface during the seasons.

	The key phrase here is "thousands of years".  The global warming
problem, short-term, may happen in hundreds of years.  Hence, processes such
as tree species migration, which occur over thousands of years, may not
be able to keep up.

: 	For the Northern Hemisphere, the variations are from a hot summmer
: and a cold winter to a mild summer and a mild winter. When the summers are 
: mild, then less snow melts than falls in the winter; the glaciers grow,etc.
: 	The other key to the Ice Age is Plate tectonics. Normally ocean
: currents carry warm water from the equator to the poles. the poles are 
: currently blocked by land masses, so there is no heat transfer at all.

	Not exactly true.  The Gulf Stream, for example, carries a
significant amount of heat northward toward Europe, which is why northern
latitude England has much milder winters than Quebec, which is at roughly
the same latitude.
	Furthermore, deep bottom currents transfer cold (from the air)
southward.  Most ocean bottom water formation occurs around Greenland.  A
lesser amount of bottom water formation occurs around Antarctica.
	BTW, the North Pole is not blocked by a land mass.


: 	The Milankovitch cycle fits the paloebiological record for temperature
: changes very well. 

	This has recently come into question.  See recent references by
Isaac Winograd, U.S. Geological Survey.  Winograd does not see Milankovitch --
Ice Age correlation.


: 
: 	You can see the Milankovitch Cycle driving temperature changes if 
: you live near tyhe mountains or in Canada. Locate the treeline. Notice the
: absence of seedlings. Only mature specimens. I we were getting warmer, the
: treelines would show growth; but they don't. Anyone can see this with 
: thweir own eyes, they don't need special equipment. You don't even need the
: absolute treeline--just find the treelinf for a specific species.
:
	I seriously doubt, given the timescale for Milankovitch-cycle climate
change, that such observations are driven by Milankovitch cycles.  Many
shorter time-scale processes will affect species distributions.  Resistance
to soil acidification comes to mind.  (Alpine soils are notably thin and
susceptible to acidification.)
	Also, an overpopulation of deer might overbrowse nice juicy pine
seedlings.  

: 	Global warming is a lie.

	Current accepted data show warming beginning in the 1930's through
today.  The link between warming and anthropogenic greenhouse gas emissions
has not yet been established with certainty.
	There IS a difference between short- and long-term climate change.
Furthermore, if you're willing to wait about 10,000 years, all of the
CO2 in the atmosphere will be absorbed by the oceans and neutralized by
dissolution of sedimented CaCO3 (see references by Broecker.)
	The "global warming" problem addresses what may be a drastic change
in global mean temperatures over a century or so.


: 
: 	The book to read is called Ice Ages by J and K Imbries. Its easily
: available at most libraries. Its a real good read. See alsos the books by EC
: Peilou, the canadian naturalist.
: 
: -Austin Moseley
: 


	I hope the relevant arguments are a bit clearer now.

	Jim Acker
	jgacker@neptune.gsfc.nasa.gov
Newsgroups: rec.backcountry