Hi Stephen,
You’re right, in the final version we should word that better. Thanks! I think that doing this for solar reduction (clearly a first but not a last step) suggests that the tropospheric climate response to an imposed radiative forcing is, in climate models, pretty linear for reasonable range of forcing (for many variables). So that would give reason to believe that a linear dynamic emulator could also be developed for MCB, but yes, it would be different from this emulator (that is, the same methodology may work, but the specific answer will be different; we didn’t say that and should have). An emulator developed specifically for strat aerosols might look a lot closer to the emulator developed here, though still won’t be quite the same (and there are other nonlinearities in the stratospheric response to aerosols that don’t show up when looking at solar reduction, we note some of these in the conclusions). doug From: [email protected] [mailto:[email protected]] On Behalf Of Stephen Salter Sent: Monday, June 27, 2016 7:13 AM To: [email protected] Subject: Re: [geo] ACPD - Multi-model dynamic climate emulator for solar geoengineering Hi All We can see how important climate emulators are by plotting a graph of days of reliable forecasts against the computing power needed by global climate models to produce them. Unless there is a dramatic improvement in computer technology the heat produced by the computer for decade predictions will itself be affecting the climate. The paper says that solar reduction is used as a proxy for any approach that reduces incoming short-wave radiation. Niemeier et al. in doi:10.1002/2013JD020445 figure 7 showed that thiis was sound for stratospheric sulphur but not for tropospheric sea salt. Can emulators sort out the difference? Stephen Emeritus Professor of Engineering Design. School of Engineering, University of Edinburgh, Mayfield Road, Edinburgh EH9 3DW, Scotland [email protected] <mailto:[email protected]> , Tel +44 (0)131 650 5704, Cell 07795 203 195, WWW.homepages.ed.ac.uk/shs <http://WWW.homepages.ed.ac.uk/shs> , YouTube Jamie Taylor Power for Change On 27/06/2016 07:55, Andrew Lockley wrote: http://www.atmos-chem-phys-discuss.net/acp-2016-535/ Multi-model dynamic climate emulator for solar geoengineering : 24 Jun 2016 Abstract. Climate emulators trained on existing simulations can be used to project the climate effects that would result from different possible future pathways of anthropogenic forcing, without relying on general circulation model (GCM) simulations for every possible pathway. We extend this idea to include different amounts of solar geoengineering in addition to different pathways of green-house gas concentrations by training emulators from a multi-model ensemble of simulations from the Geoengineering Model Intercomparison Project (GeoMIP). The emulator is trained on the abrupt 4 x CO2 and a compensating solar reduction simulation (G1), and evaluated by comparing predictions against a simulated 1 % per year CO2 increase and a similarly smaller solar reduction (G2). We find reasonable agreement in most models for predicting changes in temperature and precipitation (including regional effects), and annual-mean Northern hemisphere sea ice extent, with the difference between simulation and prediction typically smaller than natural variability. This verifies that the linearity assumption used in constructing the emulator is sufficient for these variables over the range of forcing considered. Annual-minimum Northern hemisphere sea ice extent is less-well predicted, indicating the limits of the linearity assumption. For future pathways involving relatively small forcing from solar geoengineering, the errors introduced from nonlinear effects may be smaller than the uncertainty due to natural variability, and the emulator prediction may be a more accurate estimate of the forced component of the models' response than an actual simulation would be. Citation: MacMartin, D. G. and Kravitz, B.: Multi-model dynamic climate emulator for solar geoengineering, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-535, in review, 2016. -- 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] <mailto:[email protected]> . To post to this group, send email to [email protected] <mailto:[email protected]> . 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] <mailto:[email protected]> . To post to this group, send email to [email protected] <mailto:[email protected]> . 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.
