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Re: fHuman vs. natural influences on the environment



Dale Wagner wrote:
> 
> charliew wrote:
> >
> > >Global warming is going to happen over one or two lifetimes.
> >  If
> > >it occurs as predicted, it's simply the equivalent of a
> > Pinatubo on
> > >the plus side, happening a couple of times per decade, and
> > cumulative
> > >instead of a one-time event.
> >
> > Admittedly, there are events which have altered the
> > atmosphere's temperature.  However, if the probability is
> > almost nil over one lifetime, I do not consider these events
> > to be particularly relevant.  Regarding your statement that
> > global warming is going to happen over one or two lifetimes,
> > there are a couple of questions that may impact what we want
> > to do about it.
> >
> > How much warming will occur?
> >
> > How much will occur over a specified time period?
> >
> > Is this change so fast that nature cannot adapt to it?
> >
> > Is this change so fast that man cannot adapt to it?
> >
> > One pattern I have noticed in these postings is that people
> > seem to insist that no environmental impact whatsoever occur
> > as a result of human activities.  There is even an
> > implication that humans intervene in a way that we keep
> > everything constant where it is.  These implications do not
> > seem reasonable to me.  In other words, if you want to lessen
> > the impact that humans have on this planet, a good place to
> > start is with the number of humans on this planet.  Some of
> > the posters in this group may be addressing the symptom,
> > rather than the problem.------------------------------------------------
> What is the big deal about global warming?  I was taught that when the
> earth warms we have more rain and snowfall so the glaciers increase and
> that refacts more of the solar energy so we cool off again.

Well, you weren't taught very much.  I suggest you read some up to date
science on this subject.   Jan Schloerer has posted a FAQ in
sci.environment which you should try to find.   It goes over the basics
in very understandable language and it also gives you many references
for further reading.

To refer specifically to what you said above, it is true that as
temperature goes up, the atmosphere holds more water vapor.   However,
this water vapor need not condense in droplets to form clouds or fall as
precipitation.   It can remain in the atmosphere.   Water vapor is a
very strong greenhouse gas.   That is, it is transparent to visible
light which heats the surface.   However, the surface then radiates back
at lower frequencies which water vapor is not transparent to.   So the
water vapor (and other greenhouse gases) absorbs this radiation and
reradiates it in all directions including back towards the surface.  The
net result is that the surface is warmer than it would be otherwise.
This basic science is rather elementary and it is what is referred to
when scientists discuss the greenhouse effect.   Moreover, it is not in
question.   If this effect did not operate, it is generally agreed that
the surface of the earth would be about 33 deg C colder, and life would
not be possible.  (I remember learning this in junior high school
science in the 40s.)   What the dispute is about is what happens if we
increase the concentration of other greenhouse gases such as Carbon
Dioxide.  The most plausible scenario is that the temperature will begin
to rise and that as a result the amount of water vapor will go up which
in turn will lead to an even greater increase in temperature.  This is
what most climatologists believe.  One prominent critic, Richard
Lindzen, disagrees and thinks that increased temperatures will lead to a
change in global convection in the tropics and that this will in effect
dry the atmossphere overall.   However, his theory has yet to be proved
correct and has not won many followers among his peers.   In any case,
it does appear that if other greenhouse gases are increased
exponentially, as will happen if we continue business as usual, then
climate must necessarily change, even if average global temperatures
don't increase.   The alternative you seem to be suggesting, increased
albedo due to more clouds and ice cover, would in fact amount to
significant climate change, and its precise effects on weather and
climate would not necessarily be benign.   The point is that there is a
lot of energy involved in these processes, and by the laws governing
radiation of energy, it can't just disappear.
-- 
Leonard Evens       len@math.nwu.edu      491-5537
Department of Mathematics, Norwthwestern University
Evanston Illinois


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