Path: utzoo!mnetor!uunet!seismo!sundc!hadron!rlgvax!jsf
From: jsf@rlgvax.UUCP (Steve Fritzinger)
Newsgroups: sci.misc
Subject: Re: global climates / greenhouse effect
Message-ID: <933@rlgvax.UUCP>
Date: 3 May 88 13:43:49 GMT
References: <1012@spdcc.COM>
Organization: Computer Consoles Inc, Reston VA
Lines: 50
Summary: Pointer to Scientific American article

In article <1012@spdcc.COM>, eli@spdcc.COM (Steve Elias) writes:
> some less important factors affecting climatic evolution:
> 
		.
		.
		.
> 10 -- the presence of life -- can change albedo (plants good absorbers)
>       can change atmosphere, plants reduced CO2, added O2, reduce g.h. effect.
> 
> question: does life act to stabilize conditions so they are suitable for life?
> this is the "Gaia" hypothesis of Margolis & Lovelock.  most doubt the control/
> feedback is so profound...
> 
> (finally, Drake discusses the 'continously habitable zone' -- the radius
> around a star at which life-giving temperatures can be maintained.)
> 
> one study (Michael Hart) computed that the radius for our sun is 
> between .95 and 1.01 AU...  (there were some miscalculations in the study.)

The February 1988 issue of Scientific American contains an article 
on the Goldilocks Problem (Why is Mars too cold, Venus too hot and the
Earth just right?)

The authors propose that geological proccesses, and the oceans form
an active feedback loop that regulates the Earth's temperature.  Basically
rain washes CO2 out of the atmosphere and into the ocean where it is bound
into CaCo3.  Subduction eventually drives the CaCO3 rich layer under a
continental plate, where it is heated and the CO2 released.

If the climate becomes hotter, there is more rain, which removes CO2 from
the atmosphere, cooling the planet.  Conversely if the climate cools off
there is less rain, resulting in a CO2 build up, and a warming trend.
The authors estimate that given current rates of CO2 release, if the 
oceans ever completely froze over (stopping rainfall, and allowing 
a rapid CO2 build up) the resulting greenhouse would return the planet's
temp. to about 50 deg C. in 20 million years.

The article also explains how this model could have failed on Mars
resulting in a cold frozen world, and on Venus causing it's runaway
Greenhouse.

In a letter to the editor in the April issue a reader whimsically
answers the Goldilocks Problem with "Because Earthlings are asking
the question."

-- 
Steve Fritzinger
CCI-OSD Reston VA.   uunet!rlgvax!jsf
Who's the monster that's really swell?  G-R-E-N-D-E-L
What's the thing that he does best?  N-E-M-E-S-I-S