----- Original Message ----- From: "William M Connolley" <[EMAIL PROTECTED]> Newsgroups: gmane.science.general.global-change Sent: Sunday, September 10, 2006 3:57 AM Subject: [Global Change: 610] Re: "Tipping points" again
> > > On Sat, 9 Sep 2006, Don Libby wrote: >> 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? > > Try: > http://en.wikipedia.org/wiki/Image:Holocene_Temperature_Variations.png > > -W. This image shows a maximum anomaly less than 2 deg C, which conflicts with statements that arctic temps were 3 deg C higher 5-10k ybp. Perhaps I am confusing average temps above the arctic circle with global average temps? WHEN THE CANADIAN ARCTIC WAS 5°C WARMER THAN TODAY J.P. Briner et al., Quaternary Research. Volume 65, Issue 3, May 2006 Numerous proxies, including chironomid-inferred July air temperatures, diatom-inferred lakewater pH, and sediment organic matter, reveal a pronounced Holocene thermal maximum as much as 5°C warmer than historic summer temperatures from 10,000 to 8500 cal yr B.P. A wider look puts the estimated Holocene Thermal Maximum between 0.8 and 2.4 deg C : Holocene thermal maximum in the western Arctic (0-180deg W) D.S. Kaufman, et al Quaternary Science Reviews 23 (2004) 529-560 And from Greenland proper - it would appear that the ice sheet survived the Eemian Thermal Maximum: Here we present an undisturbed climate record from a North Greenland ice core, which extends back to 123,000 years before the present, within the last interglacial period. The oxygen isotopes in the ice imply that climate was stable during the last interglacial period, with temperatures 5 degC warmer than today. K. K. Andersen, et al NATURE , VOL 431, 9 SEPTEMBER 2004 So, to my rather less expert eyes, it would appear that stabilization at 440 ppmv may be adequate to preserve a substantial portion of the Greenland ice sheet for several thousand years. Is this a reasonable doubt? -dl --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups Global Change ("globalchange") newsgroup. Global Change is a public, moderated venue for discussion of science, technology, economics and policy dimensions of global environmental change. Posts will be admitted to the list if and only if any moderator finds the submission to be constructive and/or interesting, on topic, and not gratuitously rude. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/globalchange -~----------~----~----~----~------~----~------~--~---
