Thanks for clarification, Reto. However, where I come from if something is declared irreversible there are no exceptions. A more accurate statement (though perhaps less philosophically diplomatic given the likely personalities involved) might have been “Anthropogenic climate change and ocean acidification resulting from CO2 emissions are completely reversible, though only on 100 kyr time scales via natural land and ocean CO2 removal processes (e.g., Archer et al. 2009). However, interventions to accelerate this CO2 removal by enhanced natural or by artificial means have been proposed (rather large citation list), and could potentially hasten the return to "safe" CO2, climate and ocean chemistry conditions. Further research is needed to evaluate these possibilities, especially if we continue to fail to manage atmospheric CO2 concentrations by other means."
Care to share with us how the original IPCC wording was hammered out and by whom? Regards, Greg >________________________________ > From: Knutti Reto <[email protected]> >To: "[email protected]" <[email protected]>; "[email protected]" ><[email protected]>; Geoengineering <[email protected]> >Sent: Thursday, March 6, 2014 2:21 PM >Subject: RE: [geo] NAS-Royal Society report - recent new report release > > > > >From a perspective of climate change commitment, the warming resulting from >past emissions (zero emission commitment) stays for centuries and does not go >away, so in that sense is irreversible (unlike for methane for example where >temperature would drop quickly after stopping emissions). Of course it is not >truly irreversible. It is reversible to a large degree (as shown in various >papers cited below) if we were to remove the CO2. I don’t think anyone would >disagree, and to me it’s a question of how what we mean by irreversible (see >for example IPCC WG1 section 12.5.5.1). > >In IPCC AR5 we even say this in the Summary for Policymakers: “A large >fraction of anthropogenic climate change resulting from CO2 emissions is >irreversible on a multi-century to millennial time scale, except in the case >of a large net removal of CO2 from the atmosphere over a sustained period. >Surface temperatures will remain approximately constant at elevated levels for >many centuries after a complete cessation of net anthropogenic CO2 emissions.” > (my emphasis) (Section E.8, page 28) > >Whether net removal of CO2 is plausible, desirable, likely,… is a separate >question. > >Reto > >---------------------------------------------- >Reto Knutti >Institute for Atmospheric and Climate Science >ETH Zurich >Universitätstrasse 16 (CHN N 12.1) >CH-8092 Zurich, Switzerland >[email protected] >http://www.iac.ethz.ch/people/knuttir >Phone: +41 44 632 35 40 >Fax: +41 44 632 13 11 >---------------------------------------------- > > >From:[email protected] [mailto:[email protected]] >On Behalf Of Greg Rau >Sent: Donnerstag, 6. März 2014 21:47 >To: [email protected]; Geoengineering >Subject: Re: [geo] NAS-Royal Society report - recent new report release > >Thanks Ron. In fairness, this is a report on climate change evidence and >causes, not solutions. Nevertheless, they couldn't resist some leakage into >the prescriptions side: >"Citizens and governments can choose among several options (or a mixture of >those options) in response to this information: they can change their pattern >of energy production and usage in order to limit emissions of greenhouse gases >and hence the magnitude of climate changes; they can wait for changes to occur >and accept the losses, damage and suffering that arise; they can adapt to >actual and expected changes as much as possible; or they can seek as yet >unproven ‘geoengineering’ solutions to counteract some of the climate changes >that would otherwise occur. Each of these options has risks, attractions and >costs, and what is actually done may be a mixture of these different options. >" pg. B9. > >And yes, the following statement has yet to be proven - "The current >CO2-induced warming of Earth is therefore essentially irreversible on human >timescales. The amount and rate of further warming will depend almost entirely >on how much more CO2 humankind emits." >Not surprisingly echoing the Matthews and Solomon paper to which Klaus and I >dared to offer a rebuttal: >http://www.sciencemag.org/content/340/6140/1522.2.full > > >I would be more concerned about the upcoming NAS report on geoengineering >where the true colors and biases of those involved will be in full view: >http://nas-sites.org/americasclimatechoices/study-in-progress-geoengineering/ >Very unfortunately, SRM and CRD will be discussed in the same report, and no >doubt by some in the same breath. As I noted on Feb 21, the involvement of the >CIA with the NAS in a geoengineering study (part of this report?) ought to >really bring out the chemtrailers: >http://www.motherjones.com/politics/2013/07/cia-geoengineering-control-climate-change > >In any case, this report is likely to influence CRD policy, in particular >critically needed, supportive R&D policy, for years if not decades. One can >only hope that NAS will not feature the APS's 2011 DAC report as conclusive >evidence that sucking CO2 out of the air is hopelessly expensive and call it a >day, but I'm not holding my breath. Meantime, 55% of our CO2 emissions are >annually removed from air for free. Is it inconceivable that we couldn't >proactively, safely, and very cost effectively increase this fraction by some >amount? We might never find out if certain very influential forces have their >way. >Greg > > >>________________________________ >> >>From:Ronal W. Larson <[email protected]> >>To: Geoengineering <[email protected]> >>Cc: Greg Rau <[email protected]>; Ken Caldeira <[email protected]> >>Sent: Thursday, March 6, 2014 11:08 AM >>Subject: [geo] NAS-Royal Society report - recent new report release >> >>List: cc Drs. Caldeira and Rau >> >> 1. I hope we can have some comment on last week's release of the NAS - >>Royal Society report entitled: >>A Discussion on Climate Change: Evidence and Causes >> It can be downloaded for free at >>http://nas-sites.org/americasclimatechoices/events/a-discussion-on-climate-change-evidence-and-causes/ >> I had been relatively happy with it until yesterday when a friend noted >>it seemed to be arguing for irreversibility in the answer to the last >>question (#20) - which showed no hint of carbon dioxide removal as an option. >>The entire text for Q20 reads (emphasis added): >> >>"If emissions of greenhouse gases were stopped, would the climate return to >>the conditions of 200 years ago? >> >>No. Even if emissions of greenhouse gases were to suddenly stop, Earth’s >>surface temperature would not cool and return to the level in the >>pre-industrial era for thousands of years. If emissions of CO2 stopped >>altogether, it would take many thousands of years for atmospheric CO2 to >>return to ‘pre-industrial’ levels due to its very slow transfer to the deep >>ocean and ultimate burial in ocean sediments. Surface temperatures would stay >>elevated for at least a thousand years, implying extremely >>long-term commitment to a warmer planet due to past and current emissions, >>and sea level would likely continue to rise for many centuries even after >>temperature stopped increasing [Figure 9]. Significant cooling would be >>required to reverse melting of glaciers and the Greenland ice sheet, which >>formed during past cold climates. The current CO2-induced warming of Earth is >>therefore essentially irreversible on human timescales. The amount and rate >>of further warming will depend almost entirely on how much more CO2 humankind >>emits. “ >> >> 2. There is also a figure associated with this taken from a paper >>by Zickfeld etal, found at: >>http://www.elic.ucl.ac.be/modx/users/thierry/articles/2013_Zickfeld_et_al_JClim.pdf >>which does talk about negative emissions, albeit not very positively. This >>perhaps justifies the above term “essentially”, but I still feel that a quite >>pessimistic and gloomy outlook is given, that should seem unjustified to >>anyone believing in CDR as a necessity and possibility (as I do). >> >> 3. The public release event last week of 1.5 hours can be viewed at >>https://vimeo.com/88282420 . Four of the principal authors (Brian Hoskins, >>Eric Wolff, Benjamin Santer, Inez Fung) gave brief comments on the report >>and the process - in response to questions from a reporter and maybe 10 from >>an audience at NAS headquarters. They all responded fine, but see one >>question below. >> >> 4. Re Geoengineering being something to consider, Hoskins and >>Fung answered a question in the 63 - 68 minute timeframe using the word, >>saying it was the fourth of four actions that could be taken. The report >>says (last page): >>“….or they can seek as yet unproven ‘geoengineering’ solutions to counteract >>some of the climate changes that would otherwise occur. “ >>They apparently wanted to be sure that the audience in the room knew that >>they intentionally did not talk about either SRM or CDR. They emphasized >>that the graph in Question 20 makes no mention of either SRM or CDR because >>they didn’t want to get into those topics. But I now interpret (I hope >>correctly??) that irreversibility was being ruled out, as they apparently >>would include CDR as part of geoengineering. My preference is that they had >>said something about at least afforestation/reforestation (Jim Hansen’s >>approach to CDR) - as nice credit was give about Hansen’s early warnings. >> >> 5. Other questions were on a major release arctic methane release. >> Near the 69 minute mark there was question on costs - but no specific answers >> >> 6. Dr. Fung said (my version, not from a transcript) just before >>the 96 minute mark (after a question suggesting 25%-40% CO2 removal): >> “ Because we have put this much heat into the system - removing that >>CO2, you still would have that heat in the system. It would take a very long >>time. And so we would still be warmer than in 1800." >>This indicates to me that it could be that she truly believes in >>irreversibility. That one can reduce CO2, but not temperatures - which, if >>true, would argue against CDR. But I don’t believe such irreversibility to >>be true, and I am hoping she doesn’t either. >> a. One piece of counter-evidence is from Drs. Cao and Caldeira in >> http://iopscience.iop.org/1748-9326/5/2/024011/fulltext/, showing a rapid >>fall in surface temperature after a hypothetical complete removal of CO2. >> b. Another is similar by Dr. Andrew Lacis in >>http://www.giss.nasa.gov/research/briefs/lacis_01/ >> c. Another is in several analyses by Dr. Hansen. One, showing >>rapidly falling temperatures after afforestation in figure 9 (with CO2 >>decline in Figure 5) in: >> >>http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0081648 >> >> 7. I repeat that overall the report is helpful in providing counter >>evidence to climate deniers. But this is to hope that others can comment on >>how else to interpret Dr. Fong's comment at the 96 minute spot. I am sure >>she knows several orders more in magnitude than myself about almost any >>climate topic, but I fear that those arguing against CDR will find comfort in >>her words and the above answer to Q 20. Can anyone offer a good explanation >>of these “anti-CDR” (pro-irreversibility) remarks? I note for Dr. Rau (who >>has complained on this list about “irreversibility”) that Dr. Susan Solomon >>is a co-author of this new report. >> >>Ron >> >> >> >>-- >>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. >>For more options, visit https://groups.google.com/groups/opt_out. >> >-- >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. >For more options, visit https://groups.google.com/groups/opt_out. -- >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. >For more options, visit https://groups.google.com/d/optout. > > > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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