Dear Oliver, The effects of changing the ratio of direct to diffuse radiation on plants needs further investigation. I know that after each large volcanic eruption of the past 50 years, the CO2 sink increased as plants benefited on average from the enhanced diffuse radiation and photosynthesis increase. But the overall effects of a permanent change like this on each individual species, and on agricultural yield, needs further investigation. See Figure 4 and associated references on this topic in:
Robock, Alan, 2003: Introduction: Mount Pinatubo as a test of climate feedback mechanisms, in Volcanism and the Earth’s Atmosphere, Alan Robock and Clive Oppenheimer, Eds. (American Geophysical Union, Washington, DC), 1-8. http://climate.envsci.rutgers.edu/pdf/VEAChapter1_Robocknew.pdf As for effects on solar power, there are two types of systems that concentrate direct solar radiation for electricity generation, thermal and photovoltaic (PV). The thermal systems need enough energy to boil water, which then drives turbines. Observations from Hawaii show reductions of more than 30% in direct solar radiation after the 1982 El Chichón and 1991 Mt. Pinatubo eruptions (the Pinatubo reduction was a little less than this, as only the edge of the cloud went over Hawaii). This many be enough to completely shut down the thermal systems, as first pointed out by Mike MacCracken. As for PV systems, the reduction in power would only be proportional to the reduction in insolation. For the observations on the decrease in direct radiation, see Fig. 2 of: Robock, Alan, 2000: Volcanic eruptions and climate. Rev. Geophys., 38, 191-219. http://climate.envsci.rutgers.edu/pdf/ROG2000.pdf 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 Thu, 4 Dec 2008, Oliver Wingenter wrote: > > Dear Alan, > > Could you please tell us again about reason "4. Effects on plants of > changing the amount of solar radiation and partitioning between direct > and diffuse" specifically about the impact on direct gain solar > structures such as passive solar building and concentrating > collectors. > > Thank you, > > Oliver Wingenter > > PS Dear Alvia, thank you for furnishing Alan's slides. > > On Dec 4, 5:19 pm, "Alvia Gaskill" <[EMAIL PROTECTED]> wrote: >> From the AMS website, here is Alan Robock's somewhat acerbic presentation to >> the 40 people in suits from think tanks + scientists on Nov. 21. Most of >> this information has been discussed here before, but of note is that we now >> appear to be down to 13 reasons to be against geoengineering with aerosols. >> I would call that progress. >> >> Also, in Slide 21, he states: "We need a well funded research effort, >> through the national climate program [what's that? AG], to examine the >> efficacy and dangers of different proposed geoengineering schemes, and to do >> engineering studies of the means of doing geoengineering. Small scale field >> tests of stratospheric geoengineering cannot be done; you would have to >> actually do geoengineering in the real world to test it." >> >> It really depends on how one defines small scale and what would be tested. >> I agree that to determine the impact on global climate using stratospheric >> aerosols would require at least hundreds of thousands of tons of precursor >> gas and probably 6 months to produce a sufficient stratospheric burden whose >> impacts would have to be followed for at least a full cycle of the seasons. >> The quantity required for an Arctic-only test is a little less certain, >> although will likely be a lot more than its proponents have estimated due to >> the spread southward. >> >> Field tests to determine the type of aerosol produced and how to maximize >> the formation of the most efficient sunlight scattering droplets would >> likely require a lot less, although that is also uncertain at present. >> >> While I agree with some of Alan's points, the way in which this subject >> matter is presented, including the "mug shot" side-by-sides of Crutzen and >> Wigley and the Dr. Evil magazine cover are obviously intended to turn the >> audience off to even considering the idea of stratospheric aerosol >> geoengineering. As scientists, we can and should be able to do better than >> this. >> >> Robock%20GeoEngineering17AMScongressionalBriefing.pdf >> 2444KViewDownload > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
