List, Andrew, John , David , Ken Andrew - I have re-read the paper you have cited below and decided to try to put the numbers there into the context of the paper by Dr. David Wasdell that you alerted us to on the 20th - which I also. found fascinating. For others, I am referring to a large body of work on climate feedbacks that can be found at http://www.apollo-gaia.org/. The specfic one of most pertinence to this discussion and comparison to the Davis-Caldeira Science article (that you cite below) is at:
http://www.apollo-gaia.org/Climate%20Sensitivity.pdf Using the numbers from the recent (Science-Davis-Caldeira) cite, I find (from the right hand sides of their figure 1 C (for ppm CO2) and figure 1d - for temperature rise, presumably above the 280 ppm level), those three points fall slightly below the straight line that Dr. Wasdell terms the "Charney sensitivity". Dr. Hansen would be about 2.5 times higher in predicted temperature and Dr. Wasdell about 3 times higher (both including positive feedbacks that I believe all would agree are not included in the Davis-Caldeira pape)r. This is not meant to be a criticism of theDavis Caldeira paper - as they clearly stated which model they were employing to come to their conclusions - and there are many valuable conclusions there. But I do think it important in the current discussion (see the thread title) on Hansen to point out this factor of 2.5 - which (by Dr.Wasdell) could be a factor of 3. Everyone seems convinced that the current breed of models is leaving out a lot - and apparently mostly of the positive freedback character. I don't believe that message is being heard at all clearly by the general population (which is what Andrew is betting his $100 on). For those who have not read the Wasdell analysis, his higher curve is justified by experimental (not theoretical) results attributed to three publications of other investigators besides Dr. Hansen - namely (in shorthand) Engelbeen (Vostok), Pagani (Paleo), and Kiehl (100 Ma history). They together validate (amazingly closely) his climate senstivity proposal of 7.8 degrees at 560 ppm (doubling). Davis-Caldeira are at about 2.5; Hansen at 6 degrees. Also need to point out that Dr. Hansen sees about a 50 ppm drop from "geoengineering" only with 100 Gt C of new forests -which can be amplified a good bit when combined with Biochar. I include John Nissen as a cc - as this "Wasdell" approach strongly supports his proposal to move faster generally because of the positive feedback that is surely not being considered in the Davis-Caldeira model - but is so apparent already in the Arctic. ANd is the reason for this thread. I hope someone closer to this than myself can explain how slow the missing feedbacks might be - and why. From what I have read there have been some pretty dramatic quick "flips" in the past. Ron ----- Original Message ----- From: "Andrew Lockley" <andrew.lock...@gmail.com> To: "John Nissen" <johnnissen2...@gmail.com> Cc: "geo-engineering grp" <geoengineering@googlegroups.com> Sent: Monday, July 25, 2011 11:49:48 AM Subject: Re: [geo] Jim Hansen : 1 to 2DegC and 20m sea level rise For an alternative perspective on committed warming, note the following: Comment in SciAm http://www.scientificamerican.com/article.cfm?id=guaranteed-global-warming-with-existing-fossil-fuel-infrastructure Paper in Science http://www.sciencemag.org/content/329/5997/1330.abstract "Slowing climate change requires overcoming inertia in political, technological, and geophysical systems. Of these, only geophysical warming commitment has been quantified. We estimated the commitment to future emissions and warming represented by existing carbon dioxide–emitting devices. We calculated cumulative future emissions of 496 (282 to 701 in lower- and upper-bounding scenarios) gigatonnes of CO2 from combustion of fossil fuels by existing infrastructure between 2010 and 2060, forcing mean warming of 1.3°C (1.1° to 1.4°C) above the pre-industrial era and atmospheric concentrations of CO2 less than 430 parts per million. Because these conditions would likely avoid many key impacts of climate change, we conclude that sources of the most threatening emissions have yet to be built. However, CO2-emitting infrastructure will expand unless extraordinary efforts are undertaken to develop alternatives." The authors note the pending expansion of infrastructure. I can't access the paper, so I can't see the assumptions used. However, I strongly suspect that it won't include Schaeffer's methane estimates (see summary comment on Climate Progress http://thinkprogress.org/romm/2011/02/17/207552/nsidc-thawing-permafrost-will-turn-from-carbon-sink-to-source-in-mid-2020s-releasing-100-billion-tons-of-carbon-by-2100/). I also suspect that it won't be using the carbon cycle feedback and consequential sensitivity estimates recently exchanged on this list. Even so, it comes out at just under 1.5C warming. The sociological and secondary committed technology is also critical. Half built plants need to be counted, as does the industrial output of carbon guzzling factories which are build, being built, or committed in the planning process. You can't only count the cars on the road, but also the ones that you can be reasonably sure will be built. If you consider the following graph http://www.unep.org/dewa/Portals/67/pdf/Black_Carbon.pdf (figure 3, P12) you can see that even with methane and black carbon controls, we're still set on exceeding 1.5C, (and that is without assumptions on methane release and other advanced carbon-cycle feedback work being incorporated, I suspect). There's also the bunker fuel sulphur controls, which have yet to feed properly into ANY climate modelling which I'm aware of. I've also looked at the Hare paper, which is already the best part of a decade out of date, and thus doesn't consider most of the new work on feedbacks, or the alarming rise in emissions. In fact, it's based on models which are in many cases considerably older than the paper itself. http://www.pik-potsdam.de/research/publications/pikreports/.files/pr93.pdf I can't express any confidence in this at the present time, for the reasons above. Furthermore, as there has been a history of underestimating emissions, I'd suggest that a mid-level emissions trajectory would be a 'best case' scenario. Even with all the above missing, I still note that the warming graphed in their 'feasible' scenario again exceeds the 1.5C danger level. Overall, I find it very frustrating that there is such a sense of 'playing catchup' in this field. The modelling of emissions controls needed seems to be a generation behind the earth system science. The world is therefore looking at a political landscape based on science which is largely out of date. Notably, AR4 contained very little of the non-linear change work. I'm looking forward to AR5, but it can't come soon enough. If the process of previous years is repeated, it will again be based on science that is essentially obsolete, even on the day of it's released. There's necessarily a lag process, but we aren't talking about tweaks, here - these are huge chasms between the state of the science for politicians and that for earth scientists. The arctic thaw is an example of the consequences of this. We've badly messed up the predictions. I maintain that with CO2 controls only, we have no possible way of preventing dangerous climate change without geoengineering. Either people agree, or maybe they don't read my posts or don't trust me with 100USD. A On 24 July 2011 18:42, John Nissen <johnnissen2...@gmail.com> wrote: > Hi Andrew, <snip> -- 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.
