Picking up on Andrew Lockley's suggestion for a distributed system: If we had 3.5 W / m2 of radiative forcing from greenhouse gases and 7 billion people on the planet (simple numbers for example), then we could imagine a system in which each nation was allowed to offset between 0 W / m2 and its population divided by 1 billion people times 0.5 W / m2.
This would give each country control according to its population, and create a system that would not be easy to turn on or off quickly. ------------ Regarding John Nissen's comments: I think that cloud whitening and stratospheric aerosols both have the potential to reduce climate risk. The risk ratings in the report were not relative to doing nothing (which may have been a better way to present things) but relative to other options. I think most of the report authors feel that high CO2 levels with the riskiest SRM scheme is likely to be lower risk than high CO2 levels with no SRM scheme. The risk ratings were for each option deployed alone at full scale. Often, this would be a suboptimal mode of deployment. In general, we rated options that were inherently patchy as riskier at full scale than options that produced a more uniform insolation reduction. Personally, I think cloud whitening schemes have many advantages over stratospheric aerosols in the short term: 1. Can be tested at small scale relatively easily. 2. Tests can be conducted in national waters if necessary. 3. Tests and deployments can be turned off very rapidly. 4. Easier to observe effects that are low in the atmosphere. 5. Can be deployed regionally, so that only a small number of countries would be primarily affected, possibly simplifying governance issues. 6. Obviously benign at very small scale. 7. May have positive effects for land hydrology in some cases (yet to be determined). The main point is that we need a research program to evaluate and develop various approaches. We tried to minimize in the press conference the horse race between options interpretation of our report and we were pleased that most reports did not focus on the horse race aspect. The authors of the report would be surprised (and saddened) if we did not learn a lot more in the coming years that would change many of our assessments. Best, Ken ___________________________________________________ Ken Caldeira Carnegie Institution Dept of Global Ecology 260 Panama Street, Stanford, CA 94305 USA kcalde...@ciw.edu; kcalde...@stanford.edu http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab +1 650 704 7212; fax: +1 650 462 5968 On Sun, Sep 6, 2009 at 11:30 AM, <xbenf...@aol.com> wrote: > > Throughout these studies, few realize that this is engineering. Learning > how the global system operates is best accomplished by experiments that > scale up as we learn, accompanied by simulations. Issues of risk are nearly > meaningless at early stages. Real risk falls as you learn. > > The death rate in aviation in its first decade was nearly 10%! Still, > people did it. > > Nor does the RAS report seem to understand how scaling of experiments > works. Maybe that's because few of them have ever done lab experiments; > simulations are a very different game--a form of theory, really. > > Gregory Benford > > > -----Original Message----- > From: John Nissen <j...@cloudworld.co.uk> > To: Ken Caldeira <kcalde...@stanford.edu> > Cc: Geoengineering <geoengineering@googlegroups.com>; Tom Wigley < > wig...@ucar.edu>; Stephen Salter <s.sal...@ed.ac.uk> > Sent: Sun, Sep 6, 2009 11:12 am > Subject: [geo] Re: Royal Society report - Temperature rebound a myth? > > > > > > > Hi Ken, > > > > We may disagree about the rebound of SRM termination, but we agree > about the sense. Indeed turning off SRM has been likened to turning > off the kidney dialysis machine of a patient with kidney failure. > (Thanks, Stephen, for that thought.) > > > > So why did the Royal Society report mark "Stratospheric aerosols" with > an H for high risk in table 3.6; and 2/5 for safety in table 5.1? You > were a member of the working group! > > > > I note that "Cloud albedo" al > so gets an H for "Regional climate > change". But isn't that a huge advantage of the method over > stratospheric aerosols - that it can be more targeted to cool > particular areas? Every way that a method can be tuned, or targeted > more closely, means that there is more scope for avoiding side-effects > - thus is a safety bonus. (Being able to turn off the SRM may also > allow you to react to unexpected side-effects - another bonus.) > > > > Cheers, > > > > John > > > > --- > > > > Ken Caldeira wrote: > See attached paper ... > > > > If you turn off solar deflection you would get rapid warming (no > overshoot, but a rapid rebound). > > > > This is not a myth that needs refuting. > > > > The question is: What does this mean? > > > > There are plenty of things that we do that, were they stopped suddenly, > we would be in big trouble. > > > > For example, if we stopped pumping oil today, our transportation system > and therefore food distribution system would grind to a halt and there > would be mass starvation. Does this mean that it would be crazy to base > a food distribution system on oil? Or does it mean, if you are going to > base a food distribution system on oil, you had better be pretty sure > you can assure a nearly continuous flow. > > > > I think the rapid rebound means that everyone will be incented to make > sure that the amount of solar radiation deflection is modulated with=0 > D > care. The fact that stopping SRM suddenly could bring big problems > means that we would take great care not to stop suddenly. > > > > If we stopped generating electricity we would be in big trouble. If we > stopped piping water we would be in big trouble. If we stopped hauling > garbage we would be in big trouble. Etc, etc. > > > > Our response to these threats is not to say: no electricity, no water > pipes, no garbage hauling, etc. Instead we say, let's assure > continuity, as best we can, of electricity, water piping, garbage > hauling, etc. > > > > > ___________________________________________________ > > Ken Caldeira > > > > Carnegie Institution Dept of Global Ecology > > 260 Panama Street, Stanford, CA 94305 USA > > > > kcalde...@ciw.edu; > kcalde...@stanford.edu > > http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab > > +1 650 704 7212; fax: +1 650 462 5968 > > > > > > > > On Sun, Sep 6, 2009 at 8:38 AM, John Nissen > <j...@cloudworld.co.uk<lt%3...@cloudworld.co.uk> > > > > wrote: > > > > > At the launch of the Royal Society report, it was explained that a > disadvantage of SRM was if you suddenly stopped it, because the > temperature would rebound due to all the CO2 that had accrued in the > meantime, with its suppressed warming effect. This "termination > effect" is expressed as a "high risk", see table 3.6 [1] with footnote > [2]. > > > > It so happens I have just looked through Tom Wigley's file on the > geoengi > neering googlegroup: > > http://groups.google.com/group/geoengineering/files > > > > > In this presentation he restricts geoengineering to the SRM type. I > found in his slide entitled "Global-mean temperature and sea level > consequences", about 2/3 way through the presentation, a comment in > yellow: "Rapid warming if geoengineering turned off - but no more rapid > than A1B." The implication of this is that the rate of temperature > increase returns to the rate if there had been no SRM. There is no > rebound of temperature. Merely the rate of temperature > increase rises to the rate that you'd expect from the level of net > forcing from CO2 in the atmosphere, etc. > > > > Thus I believe that this idea of rebound is a complete myth, and needs > to be publicly refuted. > > > > Now, one of the dangers of SRM is that a Pinatubo-like volcanic event > might occur during SRM deployment, in which case you'd want to turn off > the SRM within a year, to avoid any risk of over-rapid cooling. The > ability to rapidly turn off SRM with stratospheric aerosols or cloud > brightening, seems to me to be a very important advantage of these two > techniques, which has not been highlighted in the report. > > > > So the very fact that you can turn off SRM improves its safety, rather > than reduces it! Yet, in the report, this very fact causes SRM > engineering with stratospheric aerosols to get a low safety rating!!! > > > > Cheers from Chisw > ick, > > > > John > > > > [1] Page 35 of report, table 3.6. > > [2] Ibid, footnote: > > (h) ‘Termination effect’ refers here to the consequences of a sudden > halt or failure of the geoengineering system. For SRM approaches, which > aim to offset increases in greenhouse gases by reductions in absorbed > solar radiation, failure could lead to a relatively rapid warming which > would be more difficult to adapt to than the climate change that would > have occurred in the absence of geoengineering. SRM methods that > produce the largest negative forcings, and which rely on advanced > technology, are considered higher risks in this respect. > > > > > > > > > > > > > > > > --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
