From: tobis@meteor.wisc.edu (Michael Tobis)
Newsgroups: rec.backcountry,sci.environment,talk.environment,alt.wolves
Subject: Re: Milankovitch Cycle
Date: 23 Nov 92 23:30:47 GMT
Organization: University of Wisconsin, Meteorology and Space Science

In article <1992Nov23.120709.1@vmsb.is.csupomona.edu> cvakgaaq@vmsb.is.csupomona.edu writes:
>In article <1ek28iINNc0s@hpscdf.scd.hp.com>, sommer@scd.hp.com (Jeremy Sommer) writes:
>
>	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.
>	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.

This much is correct.

>	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.

This is garbled in the translation, but there's a grain of truth in it.
Of course, if there were no heat transfer at all, most of the planet would
be uninhabitable, for instance. It is true that the nearly-landlocked 
Arctic Ocean is believed to be a significant factor in the sensitivity
of climate to Milankovic cycles, and that before this was substantially
true, these cycles do not appear in the record. In a larger sense, the
arrangement of continents and oceans are believed to play a large role
in climate.

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

True.

>	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.

The western half of north america has experienced substantial warming in the
past two decades. I do not know if the eviednce you cite exists, but it
surely doesn't indicate ice age cycle cooling - the short term warming has
been much larger. Whether this is a signature of a global process is a
more difficult question, but that Alaska has warmed is indisputable.

>	Global warming is a lie.

What do you mean by this? Do you mean:

1) The world's mean temperature is not increasing?
2) The radiative balance does not determine the surface temperature?
3) Greenhouse gas concentrations do not determine the radiative balance?
4) Greenhouse gas concentrations are not increasing and accelerating?
5) The Milankovic forcing is larger than the greenhouse gas change forcing?
                        
If you identify which part of the argument is a "lie" it can be addressed
seriously with evidence. I assure you that most atmospheric scientists
believe the contrary of all five points above. 

>	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.

The Imbries' book is a good one, but it doesn't address the global warming 
question, and it was written (published 1979) before much of the recent work in
that area. If humanity lasts long enough, we will have to face an
ice age. The prospect of global warming is much more immediate though.
These are NOT competing hypotheses. 

If "global warming is a lie", can you explain the interest in it by the
editors of Science, Nature, Scientific American, as well as in the
journals of the atmospheric science, glaciology and oceanography
communities? What is the motivation for this conspiracy? If an ice age
were so likely, even if we were only after funding, wouldn't we be trying
to raise a scare about the plausible scenario rather than the implausible
one? And why would we be getting attention rather than disdain in the
broader based journals? This paranoid attribution of global warming to
radical green politics rather than science doesn't stand up to the least
scrutiny. Unfortunately, there are those who know little about it who
are happy to repeat this charge. It does a great disservice to us all.

The reasons to expect global warming in the next century are sound and
serious science. 

mt

PS - If you have a serious interest in this, I suggest you begin with
the Scientific American articles of July 1990 (p 36) and September 1989
(p 70) for a survey of the topic. The report of the World Meteorological
Association to policy makers is dry but nontechnical, and is the place to
begin for serious study of any particular aspect of the problem - it
will refer you to the primary literature. It is called _Climate Change:
The IPCC Scientific Assessment_ Cambridge Press, 1990. Your library ought
to have a copy, as well as of the update, _Climate Change 1992_.
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