"Don Libby" <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>... > > ----- Original Message ----- > From: "William M Connolley" <[EMAIL PROTECTED]> > > 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?
I don't think it is generally accepted that the Holocene Maximum was 3oC higher. NOAA says it was primarily a seasonal only variation (and regional), being a NH summer phenomenon. "In summary, the mid-Holocene, roughly 6,000 years ago, was generally warmer than today, but only in summer and only in the northern hemisphere. More over, we clearly know the cause of this natural warming, and know without doubt that this proven "astronomical" climate forcing mechanism cannot be responsible for the warming over the last 100 years." http://www.ncdc.noaa.gov/paleo/globalwarming/holocene.html > 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. How long were these temps maintained? > 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. WRT survial, don't forget that the key difference is the rate at which we are warming, not whatever temperature we may stabilize at. Coby --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
