Alan You imply a geoengineered Pinatubo would reduce crop productivity in a high-CO2 world.
Can you provide some argument to support the case? It's true that because of change in surface energy balance you reduce precip more than temps, so that if temps are back to pre-industrial mean the precip is down. But in a geoengineered climate, evaporation is also down. So is precipitation variability. Total precip does not determine the outcome in any simple way. My guess, supported by the studies with coupled ecosystem models, is that solar shielding would increase crop productivity and NPP vs a high-CO2 no-geo baseline. Of course, the effects would not be uniform. Yours, David -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Alan Robock Sent: April 21, 2009 6:54 AM To: Ken Caldeira Cc: [email protected]; geoengineering Subject: [geo] Re: EGU meeting, April 19-24 Dear Ken, If Mt. Pinatubo is the poster child, then this poster will contain drought in large parts of the world. You can see the figures in the Trenberth and Dai (2007) GRL paper. And don't forget, the effects of Pinatubo only lasted for a year. A 1-year climate anomaly will not be that devastating, as food reserves and trade can compensate for agricultural shortfalls. But a permanent aerosol cloud will make these effects last for decades. So your poster, using Pinatubo as an example, argues against geoengineering with stratospheric aerosols. The ozone depletion from Pinatubo tells the same story, but I have not seen a study of how large the effects of that much enhanced UV would be on the ecosystem and humans. I agree that the acid deposition would not seem to be a serious problem, as we showed in our paper now under review at JGR. Alan Alan Robock, Professor II Director, Meteorology Undergraduate Program Associate Director, Center for Environmental Prediction Department of Environmental Sciences Phone: +1-732-932-9800 x6222 Rutgers University Fax: +1-732-932-8644 14 College Farm Road E-mail: [email protected] New Brunswick, NJ 08901-8551 USA http://envsci.rutgers.edu/~robock On Tue, 21 Apr 2009, Ken Caldeira wrote: > For future sulfur emissions, see > http://www.ipcc.ch/ipccreports/sres/emission/5-20.htm > > For past sulfur emissions, see the attached paper. > > Current sulfur emissions are on the order of 50 Tg/yr and for this half > century is likely to be in the range of 50 to 100 Tg/yr. > > The EGU abstract ( > http://meetingorganizer.copernicus.org/EGU2009/EGU2009-4831.pdf) foresees > emissions rates of 5 to 10 Tg/yr for the first half of the century, which is > roughly the 10% range of current emissions, with this percentage scaling up > if greenhouse gas concentrations continue to increase and tropospheric > sulfur emissions decline. > > So, this is not negligible, but it is unlikely to be a game changer either. > > It is my view that there would need to be some mighty compelling reasons to > deploy a stratospheric aerosol system, if not only because people who > experience bad weather in subseuqent years might be incented to sue (or even > attack militarily) parties engaged in aerosol release. > > So, if we in an emergency situation acid rain, ozone loss, etc would be > among the costs taken into account before making a decision, but these costs > may not be decisive. > > I still think Mt Pinatubo is the poster child for stratospheric aerosols > approaches: We know it can cool the Earth, we know it can do this quickly, > and we know it does not immediately cause a global catastrophe. Were we > faced with a real climate emergency, there could be a lot of pressure to > exercise the Pinatubo option. I do not see that the abstract by Eliseev et > al markedly changes this picture. > > Best, > > Ken > ___________________________________________________ > Ken Caldeira > > Carnegie Institution Dept of Global Ecology > 260 Panama Street, Stanford, CA 94305 USA > > [email protected]; [email protected] > http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab > +1 650 704 7212; fax: +1 650 462 5968 > > > > On Mon, Apr 20, 2009 at 4:16 PM, John Nissen <[email protected]> wrote: > >> ** >> *Some items from the EGU programme* >> ** >> *Cryosphere - how much longer?* >> >> This should be an interesting session: >> http://meetingorganizer.copernicus.org/EGU2009/oral_programme/142 >> >> Also on cryosphere is the session chaired by Peter Wadhams: >> http://meetingorganizer.copernicus.org/EGU2009/oral_programme/196 >> >> And some potentially interesting presentations here: >> http://meetingorganizer.copernicus.org/EGU2009/oral_programme/702 >> and here: >> http://meetingorganizer.copernicus.org/EGU2009/oral_programme/706 >> >> *Geoengineering, session CL27* >> >> There seems to have been a disappointing response for this session. >> However the session does include a poster presentation from Russians on >> SRM using stratospheric sulphur aerosols: >> http://meetingorganizer.copernicus.org/EGU2009/EGU2009-4831.pdf >> I'd be interested in Ken Caldeira's comments on this. >> >> *Carbon stock management* >> >> In "carbon-constrained future", I see no mention of geoengineering: >> http://meetingorganizer.copernicus.org/EGU2009/oral_programme/143 >> For example, there is this presentation: >> >> ---- >> >> Can we control climate change risks and what does it cost? >> >> B. Metz >> >> Fellow, European Climate Foundation and former co-chair IPCC Working Group >> on Mitigation >> >> For controlling climate change risks to manageable levels global emissions >> of greenhouse gases have to start >> >> declining by 2015-2020 and need to be reduced to more than 50% below 1990 >> levels by 2050. >> >> An overview will be given of the options that exist to achieve these very >> challenging objectives. The economic >> >> reduction potential of these options will be given as well as their costs. >> >> Finally, the policies needed to realize the reduction potential will be >> discussed. >> *----* >> ** >> There seems little sense of emergency, despite the looming cryosphere >> dangers. Disappointing. >> >> Cheers, >> >> John >> >> >> >>> >> > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. 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