Hansen directly addressed the ideas of Richard Alley and Tad Pfeffer in the*Appendix * of his 2012 communication "Update of Greenland Ice Sheet Mass Loss: Exponential?<http://www.columbia.edu/~jeh1/mailings/2012/20121226_GreenlandIceSheetUpdate.pdf>" which is an excert from Hansen and Sato 2012 "Paleoclimate Implications for human-made climate change<http://www.columbia.edu/~jeh1/mailings/2011/20110118_MilankovicPaper.pdf>".
Commenting on Richard Alley's 2010 AGU Fall Meeting presentation, i.e. "Ice in the Hot Box - What adaptation challenges might we face?<http://adsabs.harvard.edu/abs/2010AGUFM.U52A..02A>", Hansen writes that all of Alley's chosen projections "approximated as linear". Hansen says "the fundamental issue is linearity versus non-linearity". Discussing his view of the available data on whether ice sheet melt at the moment can be said to be non-linear, he concludes: "it's too early to tell". He adds: "the problem is, by the time the data record is long enough to be convincing, it may be exceedingly difficult or impossible to prevent sea level rise of many meters" He discusses Pfeffer et.al. 2008 "Kinematic Constraints on Glacier Contributions to 21st-Century Sea-Level Rise<http://courses.washington.edu/ess203/RESOURCES/READING/pfeffer_sealevel_science_2008_with_suppl_info.pdf> ", Hansen states "The kinematic constraint may have relevance to the Greenland ice sheet, although the assumptions of Pfeffer... are questionable even for Greenland." Hansen notes that BAU emission scenarios "have a positive (warming) climate forcing that is increasing at a rate *dwarfing any known forcing*", he does not rule out Greenland, and points to Antarctica. He discusses the uncertainties and calls for maintaining the high precision observation now under way. In regard to Pfeffer et.al. 2008, what they wrote in their paper<http://courses.washington.edu/ess203/RESOURCES/READING/pfeffer_sealevel_science_2008_with_suppl_info.pdf>about their estimates was that they were "roughly constrained scenarios" and that they were "a most likely starting point for refinements in sea-level forecasts that include ice flow dynamics". On Monday, January 28, 2013 2:45:00 AM UTC-8, Oliver Tickell wrote: > > > http://grist.org/climate-energy/why-greenlands-melting-could-be-the-biggest-climate-disaster-of-all/ > > > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/geoengineering?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
