Ken (cc list ) I have tried (as a rank amateur observer, not participant) to follow this retreatjng September arctic ice topic for the last 5 years. I have come to a different conclusion than expressed in your two articles.. The website I have found most valuable can be located by remembering the name "Neven" - and googling with "arctic" and "ice" . This blog averages more than one message per hour - and the folks commenting there seem to be putting a lot of time into the topic. Not experts on this blog, but dedicated amateurs, who do seem to be talking to the ice experts, however.
The key question is what are we to be measuring when we talk of "gone"? I gather that 10% remainder is considered "gone". One also has to consider whether one will be talking area, extent, or volume. I like the volume definition - as thickness is dropping much more rapidly than area (the smaller number) or extent - and the volume is easier to find data on than thickness. A good (April 2011) discussion of these differences is at http://neven1.typepad.com/blog/2011/04/trends-in-arctic-sea-ice-volume.html#more This short write-up, using experimental volume data, suggests about 2016 as a best guess to get to this 10% value. This uses a "Gompertz" model - which has no particular theoretical validity - but seems to have more validity than a linear or quadratic approach to absolute zero . It might be overly conservative. For today's blog exchange (several dozen so far today), go to just the early part of the above URL. The modeler who seems (to me) to have done the best job in modeling this (the subject of Ken's two articles) is Dr. Wieslaw Maslowski who has supported this 2016 "gone" date since 2008 or so (and again this year). The following 2008 cite is given in the above URL for a Maslowski Ppt: http://www.ees.hokudai.ac.jp/coe21/dc2008/DC/report/Maslowski.pdf His work doesn't show up in literature comparisons such as in Ken's articles because his (highly detailed) model is limited only to the Arctic; it is not a global model, although of course it is linked to the rest of the world. We should also note that Maslowski has supported 2013 as not being out of the question. (and still does) I don't believe we have the luxury of relying on a "gone" date in the 2030's or even 2020's - and this is based on interpretations of recent data - not model outputs. It seems to me the lesson is that the global models need retuning. Ron ----- Original Message ----- From: "Ken Caldeira" <kcalde...@carnegie.stanford.edu> To: "geoengineering" <geoengineering@googlegroups.com> Sent: Monday, July 18, 2011 6:41:17 AM Subject: [geo] September sea-ice gone by end of century? (or much sooner) Folks, There has been a fair amount of discussion on this group that talks about imminent September sea ice loss in the Arctic. The attached paper indicates that around half of the normal September sea-ice should still be around in the 2020-2040 time frame. Boe, J., Hall, A., Qu, Z. Nature Geosci 2, 341-343 (2009). I am not saying that the situation in the Arctic is not dire, however, are the suggestions that September sea-ice in the Arctic is soon to be a thing of the past a bit overblown and without foundation? Best, Ken ___________________________________________________ Ken Caldeira Carnegie Institution Dept of Global Ecology 260 Panama Street, Stanford, CA 94305 USA +1 650 704 7212 kcalde...@carnegie.stanford.edu http://dge.stanford.edu/labs/caldeiralab @kencaldeira -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to geoengineering@googlegroups.com. To unsubscribe from this group, send email to geoengineering+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to geoengineering@googlegroups.com. To unsubscribe from this group, send email to geoengineering+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en.
