Also please see http://blogs.reuters.com/environment/2009/10/30/panic-at-2-am-the-search-for -multiyear-arctic-ice/
Ice cover is not the only issue--ice thickness also matters for it takes an extensive, pretty solid (i.e., very small or no leads) ice cover about a meter thick or more (with a bit of snow on top) to insulate the winter atmosphere from the ocean and allow ice surface temperatures to drop down to -40 or lower so that the really cold winter air masses that create the winter weather that we have depended on can form. Best, Mike On 11/2/09 10:08 AM, "David Keith" <[email protected]> wrote: > A couple of points on sea ice: > > 1. There have been a bunch of hype-rich data-poor announcements recently that > confidently predict very early dates for disappearance of summer sea ice. > There is some good evidence that people are overinterpreting interannual > variability as signal. The following is quite painful: it was the July 2009 > compilation of forecasts every single one of which overestimated the actual > sea ice loss in 2009. (I enclose a figure with the 2009 data added as an > annotation. See the following for the original report: > > http://www.arcus.org/search/seaiceoutlook/2009_outlook/july_report/downloads/g > raphs/JulyReport_JuneData_Chart.pdf > > I am deeply concerned about the rapidity of change in the Arctic, indeed > unlike most people who talk about this I spent a fair amount of time traveling > on skis high Arctic, but I'm a skeptical scientist and I know that uncertainty > cuts both ways. I also am keenly aware that people tend to interpret noise as > signal when it goes the way they expect. > > 2. Several folks on this list talk about the ice-albedo feedback as if it is > not included in models. In fact this feedback is one of the central reasons > for the polar amplification of predicted global warming and has been in models > in various forms since the early 70s. In recent years the big focus has been > improving dynamic (including ocean currents) sea ice models. Among the things > typically not included are the (very uncertain) effect of warming permafrost > on methane emissions, this is likely not a large omission as it's very hard to > have methane emissions large enough to significantly change radiative forcing > over half-century timescales. > > 3. It does appear that the IPCC underestimated the possibility of large-scale > loss of the big ice sheets, I have run an expert elicitation > (www.ucalgary.ca/~keith/elicitation.html > <http://www.ucalgary.ca/~keith/elicitation.html> ) on the topic and our > compilation of expert judgments (almost all of whom were in IPCC) shows that > IPCC dramatically underestimated the risk. > > 4. One can make an argument that albedo geoengineering would be particularly > appropriate for the Arctic both for the obvious reason that climate change > impacts and responses are largest there, and because by increasing > reflectivity geoengineering would be nicely countering the albedo feedback > that decreases reflectivity. > > -David > > > > From: John Nissen [mailto:[email protected]] > Sent: November 1, 2009 11:54 AM > To: David Keith > Cc: [email protected]; [email protected]; Ken > Caldeira; Julian Norman; Mike MacCracken > Subject: Re: [geo] ERL papers on line > > > Thanks for the reference to the Environmental Research Letters, David. > > Only Mike MacCracken's paper considers the context for geoengineering. If we > are going to have to use geoengineering to tackle certain problems, how should > we approach it. He considers three problem areas: > 1) the warming of low-latitude oceans which contribute to more intense > tropical cyclones and coral bleaching; > 2) the amplified warming of high latitudes and the associated melting of ice > that has been accelerating sea level rise and altering mid-latitude weather; > 3) the projected reduction in the loading and cooling influence of sulphate > aerosols, which has the potential to augment warming sufficient to trigger > methane and carbon feedbacks. > > I would suggest that the amplified warming of (2) has the potential to trigger > massive methane discharge (and associated positive feedback on global warming) > of (3) as well as the potential to trigger rapid sea level rise. The retreat > of Arctic sea ice is part of the warming amplification process, so it is > crucial to prevent its summer disappearance. Do you agree, Mike? > > If you agree, then the importance of this (i.e. preventing Arctic sea ice > summer disappearance) makes the arguments against geoengineering in the other > papers seem rather irrelevant! > > Note that Mike has only considered the problems that could be addressed with > SRM geoengineering. If we consider problems such as ocean acidification, and > addressing them with techniques such biochar, then the arguments in the other > papers against geoengineering seem irrelevant to the point of absurdity - but > then perhaps the arguments were directed at SRM geoengineering alone. > > Cheers from Chiswick, > > John > > --- > > David Keith wrote: > Folks, > > There is a set of papers on geoengineering on line at Environmental Research > Letters. Ken Caldeira and I served as editors of this special issue. More > papers and a editorial will be added later. > > Cheers, > David > > > http://www.iop.org/EJ/abstract/1748-9326/4/4/045101 > > Focus on Climate Engineering: Intentional Intervention in the Climate System > 2009 Environ. Res. Lett. 4 045101 doi: 10.1088/1748-9326/4/4/045101 > <http://dx.doi.org/10.1088/1748-9326/4/4/045101> > <http://www.iop.org/EJ/help/-topic=abstract/abstract/1748-9326/4/4/045101> > > Geoengineering techniques for countering climate change have been receiving > much press recently as a `Plan B' if a global deal to tackle climate change is > not agreed at the COP15 negotiations in Copenhagen this December. However, the > field is controversial as the methods may have unforeseen consequences, > potentially making temperatures rise in some regions or reducing rainfall, and > many aspects remain under-researched. > > This focus issue of Environmental Research Letters is a collection of research > articles, invited by David Keith, University of Calgary, and Ken Caldeira, > Carnegie Institution, that present and evaluate different methods for > engineering the Earth's climate. Not only do the letters in this issue > highlight various methods of climate engineering but they also detail the > arguments for and against climate engineering as a concept. > > Further reading > Focus on Geoengineering at > http://environmentalresearchweb.org/cws/subject/tag=geoengineering > IOP Conference Series: Earth and Environmental Science is an open-access > proceedings service available at www.iop.org/EJ/journal/ees > <http://www.iop.org/EJ/journal/ees> > > Focus on Climate Engineering: Intentional Intervention in the Climate System > Contents > > Modification of cirrus clouds to reduce global warming > <http://www.iop.org/EJ/abstract/1748-9326/4/4/045102> > David L Mitchell and William Finnegan > > Climate engineering and the risk of rapid climate change > <http://www.iop.org/EJ/abstract/1748-9326/4/4/045103> > Andrew Ross and H Damon Matthews > > Researching geoengineering: should not or could not? > <http://www.iop.org/EJ/abstract/1748-9326/4/4/045104> > Martin Bunzl > > Of mongooses and mitigation: ecological analogues to geoengineering > <http://www.iop.org/EJ/abstract/1748-9326/4/4/045105> > H Damon Matthews and Sarah E Turner > > Toward ethical norms and institutions for climate engineering research > <http://www.iop.org/EJ/abstract/1748-9326/4/4/045106> > David R Morrow, Robert E Kopp and Michael Oppenheimer > > On the possible use of geoengineering to moderate specific climate change > impacts <http://www.iop.org/EJ/abstract/1748-9326/4/4/045107> > Michael C MacCracken > > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. 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