Dynamic climate emulators for solar geoengineering

• Published in: Atmospheric Chemistry and Physics
• Main Authors: MacMartin, Douglas G., Kravitz, Ben
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: European Geosciences Union 2016
• Subjects: Sea ice
• Online Access: https://doi.org/10.5194/acp-16-15789-2016

Climate emulators trained on existing simulations can be used to project project the climate effects that result from different possible future pathways of anthropogenic forcing, without further relying on general circulation model (GCM) simulations. We extend this idea to include different amounts of solar geoengineering in addition to different pathways of greenhouse 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 × CO_2 and a compensating solar reduction simulation (G1), and evaluated by comparing predictions against a simulated 1 % per year CO_2 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 being 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 a limit to the linearity assumption. © 2016 Author(s). This work is distributed under the Creative Commons Attribution 3.0 License. Published by Copernicus Publications on behalf of the European Geosciences Union. Received: 17 June 2016 – Published in Atmos. Chem. Phys. Discuss.: 24 June 2016; Revised: 18 November 2016 – Accepted: 22 November 2016 – Published: 22 December 2016. We thank all participants of the Geoengineering Model Intercomparison Project and their model development teams, CLIVAR/WCRP Working Group on Coupled Modeling for endorsing GeoMIP, and the scientists managing the Earth System Grid data nodes, who assisted with making GeoMIP output available. The Pacific Northwest National Laboratory is operated for the U.S. Department of ...