----- Original Message -----
From: "William M Connolley" <[EMAIL PROTECTED]>
Newsgroups: gmane.science.general.global-change
Sent: Saturday, September 09, 2006 2:37 PM
Subject: [Global Change: 604] Re: "Tipping points" again
>
>
> On Sat, 9 Sep 2006, Don Libby wrote:
>> The missing piece: is air temperature increase of 2-4 degrees C
>> sufficient
>> to melt the polar ice sheets over 4-5 thousand years?
>
> Gr yes; Ant no.
>
> -W.
Gr maybe - we don't really know the extent of ice cover during the Holocene
Thermal Maximum, approx 5-10 k years ago, when temps were an estimated 3
degrees C higher - do we?
Ant no - Vostok cores show temps tipping into that range about 10k ybp,
130k, 240k, 325k, and 410k - and obviously, there remained ice cover at
Vostok throughout.
So, I guess Hansen likes stabilization at 440 because it commits us to a
global warming in the neighborhood of previous warmings that the ice caps
and humans have survived - and avoids tipping into Alistair's ice-free
Eocene, perhaps.
-dl
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