[geo] Re: Sea ice: beware of hype, uncertainty cut's both ways

[John Nissen]

Thank you, David, for your thoughtful reply and the excellent points you make, which culminate in an acknowledgement of the argument for albedo geoengineering to save the Arctic sea ice, as I have been proposing.  Your support is most welcome. Re your point 1, the proposal does not assume a particular estimate for date of disappearance of Arctic sea ice.   There are two arguments here.  The first is that it better to apply the geoengineering before the positive feedback grows any stronger.  (As Mike puts it, it is better to put out a small fire rather than wait until the whole building is aflame.)  The second argument is to take the precautionary principle, and consider the soonest time for disappearance within the possible range of times.  Here the very uncertainty that you highlight is giving us a significant probability of ice summer disappearance within a few years, even if the most likely date (aka median date) may be a few decades away. Re point 2 and the models, the typical models give a "climate sensitivity" factor, which is essentially linear and assumes tipping points are not reached.  However, with the Arctic sea ice we may be seeing tipping already in progress, due to non-linear effects and positive feedbacks which are notoriously difficult to model.  Furthermore, the Arctic sea ice may never have totally disappeared in any interglacial period of the past 2 million years; and the maximum temperature of recent interglacial periods will soon be exceeded.   So we are moving into uncharted waters.  Thus the assumption that global warming will proceed linearly with CO2 (i.e. with constant climate sensitivity factor) seems debatable.  Therefore there is all the more reason to try and save the Arctic sea ice. Re point 2 and the methane, again one could argue for a precautionary approach.  Some scientist estimate that there is enough methane to more than double GHG forcing if it were released.  Halting the Arctic warming would greatly reduce the risk. Re point 3, it is good to see that experts from IPCC now acknowledge that they grossly underestimated the risk of dramatic sea level rise from Greenland ice sheet instability.  That seems as good a reason as any for urgent albedo geoengineering. >From your point 4, you do seem to be supportive of the proposal for albedo geoengineering to try and save the Arctic sea ice.  As you say, it seems sensible to counter an albedo reduction (as ice turns to water) with an albedo gain (through SRM geoengineering). Best wishes, John -- David Keith 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/graphs/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) 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:j...@cloudworld.co.uk] Sent: November 1, 2009 11:54 AM To: David Keith Cc: climateintervent...@googlegroups.com; geoengineering@googlegroups.com; 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  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 Focus on Climate Engineering: Intentional Intervention in the Climate System Contents Modification of cirrus clouds to reduce global warming David L Mitchell and William Finnegan Climate engineering and the risk of rapid climate change Andrew Ross and H Damon Matthews Researching geoengineering: should not or could not? Martin Bunzl Of mongooses and mitigation: ecological analogues to geoengineering H Damon Matthews and Sarah E Turner Toward ethical norms and institutions for climate engineering research David R Morrow, Robert E Kopp and Michael Oppenheimer On the possible use of geoengineering to moderate specific climate change impacts Michael C MacCracken   --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---