Hi all, Our latest paper is out online here: https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2018JD028906; “Timescale for Detecting the Climate Response to Stratospheric Aerosol Geoengineering”
This uses the GLENS simulations (see here: http://www.cesm.ucar.edu/experiments/cesm1.2/GLE/ if you aren’t familiar with them), but - Builds an emulator to allow us to project response to other scenarios (and in particular, to scenarios more moderate than the RCP8.5 one used in GLENS, which was great for signal-to-noise ratio but not the only case to consider for policy) - Compares the projected response from geoengineering to natural variability - Estimates how long it would take to detect changes, in a few variables, for a few scenarios. Bottom line is that if we have a limited deployment scenario (e.g., only use SRM to go from 3C to 1.5C), then in many (not all) places, it will be difficult to tell the difference between the 1.5C climate obtained by using SRM and a 1.5C climate due to lower CO2… Abstract Stratospheric aerosol geoengineering could be used to maintain global mean temperature despite increased atmospheric greenhouse gas (GHG) concentrations, for example, to meet a 1.5 or 2◦Ctarget. While this might reduce many climate change impacts, the resulting climate would not be the same as one with the same global mean temperature due to lower GHG concentrations. The primary question we consider is how long it would take to detect these differences in a hypothetical deployment. We use a20-member ensemble of stratospheric sulfate aerosol geoengineering simulations in which SO2is injected at four different latitudes to maintain not just the global mean temperature, but also the interhemispheric and equator-to-pole gradients. This multiple-latitude strategy better matches the climate changes from increased GHG, while the ensemble allows us both to estimate residual differences even when they are small compared to natural variability and to estimate the statistics of variability. We first construct a linear emulator to predict the model responses for different scenarios. Under an RCP4.5 scenario in which geoengineering maintains a 1.5◦C target (providing end-of-century cooling of 1.7◦C), the projected changes in temperature, precipitation, and precipitation minus evaporation (P−E) at a grid-scale are typically small enough that in many regions the signal-to-noise ratio is still less than one at the end of this century; for example, for P−E, only 30% of the land area reaches a signal-to-noise ratio of one. These results provide some context for the projected magnitude of climate changes associated with a limited deployment of stratospheric aerosol cooling -- 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 geoengineering+unsubscr...@googlegroups.com. To post to this group, send email to geoengineering@googlegroups.com. Visit this group at https://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout.
