Hi, I wouldn't be so sure that this is a forcing difference. There are VERY large differences in the model response to high CO2 scenarios, with much smaller differences between SRM and no-SRM scenarios. These arise because different factors act to limit vegetation productivity in the different models. In Susanne Glienke's paper the only models which included a nitrogen cycle in GeoMIP, a version of CLM, found the opposite trend to that reported in Xia et al. They found greater tropical productivity in the non-SRM scenario than the SRM scenario and only a small CO2 fertilization effect, likely arising from the fact that nitrogen is the limiting factor in these regions and it is recycled more rapidly in warmer soils boosting NPP.
I think it's still early days in the study of the vegetation response to SRM. cheers, Pete On Thursday, 11 February 2016 08:44:01 UTC-5, Alan Robock wrote: > > Dear Bala, > > Actually in our paper we say: > > Kalidindi et al. (2015) showed that with a 20 Tg sulfate aerosol > (SO4) stratospheric loading to balance the radiative forcing > of 2 xCO2, broadband diffuse radiation would increase > by 11.2 Wm-2 compared with the reference run. However > they used a very unrealistic stratospheric aerosol distribution, > with a very small effective radius of 0.17 μm and uniform > geographical distribution. > > So we did different experiments, and we used a much more "realistic" > aerosol size and space distribution. I think the differences in the > results are because of the forcing and not the models. > > Alan > > Alan Robock, Distinguished Professor > Editor, Reviews of Geophysics > Department of Environmental Sciences Phone: +1-848-932-5751 > Rutgers University Fax: +1-732-932-8644 > 14 College Farm Road E-mail: [email protected] > <javascript:> > New Brunswick, NJ 08901-8551 USA http://envsci.rutgers.edu/~robock > ☮ http://twitter.com/AlanRobock > Watch my 18 min TEDx talk at http://www.youtube.com/watch?v=qsrEk1oZ-54 > > On 2/10/2016 10:32 PM, Govindasamy Bala wrote: > > Interesting result. The conclusions seem to depend on model > configurations. > > Our paper published last year in Climate Dynamics (attached) did not find > any such benefit from the enhanced diffused radiation because of the offset > from a reduction in direct light. In fact we found a net reduction in GPP > of about 1 PgC > > Looks like Multi-model intercomparison would be needed to resolve this > issue. > > On Wed, Feb 10, 2016 at 7:39 PM, Alan Robock <[email protected] > <javascript:>> wrote: > >> Our most recent paper has just been published: >> >> Xia, L., Robock, A., Tilmes, S., and Neely III, R. R.: Stratospheric >> sulfate geoengineering could enhance the terrestrial photosynthesis rate, >> Atmos. Chem. Phys., 16, 1479-1489, doi:10.5194/acp-16-1479-2016, 2016. >> >> http://www.atmos-chem-phys.net/16/1479/2016/ >> >> -- >> Alan Robock >> >> Alan Robock, Distinguished Professor >> Editor, Reviews of Geophysics >> Department of Environmental Sciences Phone: +1-848-932-5751 >> Rutgers University Fax: +1-732-932-8644 >> 14 College Farm Road E-mail: <javascript:> >> [email protected] <javascript:> >> New Brunswick, NJ 08901-8551 USA >> <http://envsci.rutgers.edu/%7Erobock>http://envsci.rutgers.edu/~robock >> ☮ http://twitter.com/AlanRobock >> Watch my 18 min TEDx talk at http://www.youtube.com/watch?v=qsrEk1oZ-54 >> >> -- >> 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] <javascript:>. >> To post to this group, send email to <javascript:> >> [email protected] <javascript:>. >> Visit this group at https://groups.google.com/group/geoengineering. >> For more options, visit https://groups.google.com/d/optout. >> > > > > -- > With Best Wishes, > > ------------------------------------------------------------------- > G. Bala > Professor > Center for Atmospheric and Oceanic Sciences > Indian Institute of Science > Bangalore - 560 012 > India > > Tel: +91 80 2293 3428; +91 80 2293 2505 > Fax: +91 80 2360 0865; +91 80 2293 3425 > Email: [email protected] <javascript:>; [email protected] > Web:http://caos.iisc.ernet.in/faculty/gbala/gbala.html > ------------------------------------------------------------------- > -- > 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] <javascript:>. > To post to this group, send email to [email protected] > <javascript:>. > Visit this group at https://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. 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 https://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout.
