Jim asks:

> I remember reading artciles in the 70's that stated that we were heading
for
> another ice age if we did not start taking steps to preserve the
environment.
> One of my grade school teachers even brought it up in an ecology lesson.
> Now, the same groups who were projecting an ice age are clamoring about
> global warming.
>
> So which is it?  Is it getting colder or hotter?  They can't decide.  But
> over the last 30 years, temperatures have slightly declined.  Although the
> past few have seen milder winters.

Actually the two outcomes are interrelated, only making the task of
prediction all the more difficult. The notion of an ice age following global
warming (or vice versa) is called a "catastrophic cusp." In any system where
feedback processes exist, the possibilities of catastrophic cusps also exist,
and the earth's biosphere, heat budget, solar albedo and geochemical balance
are filled with such feedback loops. Predicting which one of the features of
these loops will predominate at any one point in time is like trying to
predict which way a piece of falling paper will flutter.

An idea that appeared from disparate lines of evidence in the early 1990's
was one called, "Snowball Earth." (see:

     http://www.sciam.com/2000/0100issue/0100hoffmanbox1.html

This idea that the earth was frozen over (with ice covering the oceans to
perhaps a mile depth) for millions of years was a surprise to almost everyone
involved with geophysics at the time, and the end of the snowball earth may
well be linked to the evolution of multicellularity, one of the most
pervasive mysteries left in the elucidation of life on earth. This was global
warming on steroids.

But to answer your original question, Robert Frost wrote this in 1923:

"Some say the world will end in fire,
Some say in ice.
From what I've tasted of desire
I hold with those who favor fire.

"But if it had to perish twice,
I think I know enough of hate
To say that for destruction ice
Is also great
And would suffice."

Wirt Atmar

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