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From: eugene@pioneer.UUCP
Newsgroups: sci.bio,sci.astro
Subject: Re: Mass extinctions (atmospheric energy balance)
Message-ID: <1140@ames.UUCP>
Date: Wed, 1-Apr-87 14:42:16 EST
Article-I.D.: ames.1140
Posted: Wed Apr  1 14:42:16 1987
Date-Received: Sat, 4-Apr-87 08:39:32 EST
References: <6760@alice.uUCp> <496@uokmax.UUCP> <1682@whuts.UUCP>
Sender: usenet@ames.UUCP
Reply-To: eugene@pioneer.UUCP (Eugene Miya N.)
Organization: NASA Ames Research Center, Moffett Field, Calif.
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Keywords: green house and nuclear winter
Xref: utgpu sci.bio:207 sci.astro:784

In article <1682@whuts.UUCP> wv@whuts.UUCP (54299-DUNCAN,W.) writes:
>In article <496@uokmax.UUCP> david@uokmax.UUCP (David Lee Cox) writes:
>>I really like this discussion, but am a little confused about a couple of
>>things,  What would volcanoes, or meteors do that could cause mass extinctions?
>
>I am no expert on the subject, but I have heard that if enough debris is
>deposited in the upper atmosphere (possibly by volcanoes or a collision
>of Earth with large meteors or an asteroid), a resulting cooling trend
>could change the climate quickly enough to cause mass extinctions to take
>place. If anyone could explain this further, I would like to see it 
>discussed further.
>
>							Bill

Ok, as simple as I can think of it. Because I fear you will get some
incomplete explanation.  These are examples of a class of climatic
energy balance models (big words for things like rain cycles etc.).
We will cover chemistry, physics (radiative transfer) and a bit of
astronomy and biology.

Anyway, you have a planet like the earth.  If it just sat there it
would have a temperature: cold for sure.  So we add a star which
heats the planet and eventually reaches a stable temperature.  The net
energy at stable state is 0.  If it were positive, it would be warming,
if it were negative it would cool.  The side which faces the star
transfers heat around to the dark side which radiates heat away, any
it's all stable. Oh note, we assume the star has a constant temperature
(energy) and that this is important because the color of the is
related to temperature and the distributions of light (called colors
blues, yellows, reds, but also IR, UV). More one this.

need graphics:           planet           star (assume const. output)
not to scale

           <-heat away-     O   <-heat in- O
			net energy gain == 0

The problem comes from the fact we have an atmosphere, and one of
diversely different gases.  It takes chemistry to understand the effect
of the different gases on light (energy transport mechanism).
Fortunately, the effect of the gases is simply a sum (not gestalt or
emergent effects).  The certain gases act like a filters (there are also
particulates).  The fact is this is one of the reasons why the sky is
blue and sunsets are red: the types and the distances which light
energy must travel to reach the ground (an esthetic aside!).
(closeup)
		|		^
		|		|
	sun:short wave      long wave
		|		|
		v		|
========================ground============================   Q == 0
		| absorbed: heat conducted away and "out the back side"
		v

Now assume for a moment that the atmosphere was just one homogeneous
gas with the properties of all other gases combined.  What the light
does is hit the solid earth (ooops I mentioned a planet name!) at one
frequency (short wavelength).  Some of this energy is conducted away,
some is reflected (light that you and I see), but most is converted
to a longer wavelength (IR) energy and radiated out into space (our
temperature).  This conversion of energy is critical, but it is a
bottleneck in our understanding.

Now, if you were to try and image (not view) the sun thru the atmosphere
from the surface of the earth, you would find that in the UV and IR
regions the sun is basically dark.  Very little solar UV and IR gets
thru (but still significant), most of our light is in the visible
spectrum (.55) or note: we have evolved into visible light "seeing"
creatures.  This because most of the emitted radiation from the sun
is in the visible wavelengths and because the Ozone (O sub 3), CO2, NOx
and other gases higher up filter out these wavelengths (again why the
sky is blue).  These gases BTW tend to be in the topopause and the
stratosphere.  Okay this is the stable state.

	     |  |		^
	     v  |		|
----------------------atmosphere----------------------- filtering
		|		^
		|		|
	sun:short wave      long wave (emitted, some long wave reflected)
		|		|
		v		|
========================ground============================   Q == 0

Now, change the concentrations of ozone, C02, NOx, and particulates
ala a volcano, meteor, or nuclear winter.  If ozone is destroyed
more short wave energy reaches the ground (things get warmer).

Or if more CO2 is injected into the air (here's the neat part of the
model), it gets warmer because of secondary effect: short wave light
comes in thru the CO2, turns to long-wave (IR) which tries to leave, but
CO2 is opaque to longer-wave lengths (in fact it's called a CO2 window).
This is Keeling's Green House effect (warming).  This is venus's energy
balance (comparative planetology 101).

	     |  |
	     v  |
----------------------atmosphere----------------------- CO2 filtering
		|		^  (trapped energy can't get out heat!)
		|		|
	sun:short wave      long wave (emitted, some long wave reflected)
		|		|
		v		|
========================ground============================    Q == 0

Also, relatively large particles in the air (smoke, clouds) reflect
visible light before it hits the ground (stays short wave). Preventing
ground warming (cooling).  The sum total of all this is climate
and weather (local) and can be expressed in systems of linear (largely)
and partial differential equations (a problem being the data granularity
[why weather forecasts are not better O(n^3) data requirements]).

Now the problem with long prediction is: what are the real effects?
Do we warm until we are cooked?  Or do we warm until some secondary
effect like lots of water vapor clouds and particles reflect all
incoming light and we cool and have an ice age?  Good question, wish
some one knew we could go on and solve other problems.
NOBODY KNOWS FOR SURE.  Are you can see, some of this is
a bit complex (a data management problem you just have to keep the
actions and interactions staight) but understandable
(like Eistein said).  I've oversimplified a lot.  Keep sending those tax
dollars in.

From the Rock of Ages Home for Retired Hackers:

--eugene miya
  NASA Ames Research Center
  eugene@ames-aurora.ARPA
  "You trust the `reply' command with all those different mailers out there?"
  "Send mail, avoid follow-ups.  If enough, I'll summarize."
  {hplabs,hao,ihnp4,decwrl,allegra,tektronix,menlo70}!ames!aurora!eugene