Re: Large animal extinctions: extinction-ex-astra

Timo Niroma (timo.niroma@tilmari.pp.fi)
15 Jul 1996 17:01:27 GMT

In article <4rtu9k$de@hecate.umd.edu>, "Thomas R. Holtz, Jr."
<th81@umail.umd.edu> says:
>
>timo.niroma@tilmari.pp.fi (Timo Niroma) wrote:
>
>> 1. How can you be so sure that the end of ice age did not have an
extraterrestrial
>> source?
>
>Two points of clarification:
>A) The "Ice Age" is NOT OVER!
>(snips)

I agree.

It's a question of definition.

But we must go 120,000 or 130,000 years back in history to find
temperatures warmer than today.

And to find an iceless Earth, we must go some 30 or 40 million years
backwards.

>B) (snips)
>Milankovitch-driven glacial-interglacial cycle is very, very strong.
>

That's true for the short cycle of little over 20,000 years, and also of
middle cycle of 40,000 years (the tilt of the Earth).

But the long cycle of about 100,000 years is today in great doubt.

The theory that Earth gots more heat while the orbit is round than when
it is more eccentric is disputed.

Anyway, Milankowicz cycles don't predict any sudden changes unless some
process of positive feedback is added.

I haven't seen such addendum, and both the Greenland and Vostok cores
show no evidence of such an effect.

And I also agree with you that the Sun is more variable than we have
expected.

Could cause the vacillations and oscillations during the ice age, but
probably not a rise of 14 degrees C in 1 or 2 years, or we must
throroughly change our understanding of Sun-like stars.

Timo