On solar geoengineering and climate uncertainty

Uncertain climate system response has been raised as a concern regarding solar geoengineering. We explore the effects of geoengineering on one source of climate system uncertainty by evaluating the intermodel spread across 12 climate models participating in the Geoengineering Model Intercomparison project. The model spread in simulations of climate change and the model spread in the response to solar geoengineering are not additive but rather partially cancel. That is, the model spread in regional temperature and precipitation changes is reduced with CO2 and a solar reduction, in comparison to the case with increased CO2 alone. Furthermore, differences between models in their efficacy (the relative global mean temperature effect of solar versus CO2 radiative forcing) explain most of the regional differences between models in their response to an increased CO2 concentration that is offset by a solar reduction. These conclusions are important for clarifying geoengineering risks regarding uncertainty.

[1]  Raquel V. Francisco,et al.  Uncertainties in regional climate change prediction: a regional analysis of ensemble simulations with the HADCM2 coupled AOGCM , 2000 .

[2]  J. Hansen,et al.  Efficacy of climate forcings , 2005 .

[3]  K. Taylor,et al.  Impact of geoengineering schemes on the global hydrological cycle , 2008, Proceedings of the National Academy of Sciences.

[4]  A. Grimm,et al.  Interannual Variability and Seasonal Evolution of Summer Monsoon Rainfall in South America , 2009 .

[5]  Jonathan M. Gregory,et al.  A Surface Energy Perspective on Climate Change , 2009 .

[6]  Ken Caldeira,et al.  Geoengineering as an optimization problem , 2010 .

[7]  M. Granger Morgan,et al.  Regional climate response to solar-radiation management , 2010 .

[8]  Andy Ridgwell,et al.  Assessing the regional disparities in geoengineering impacts , 2010 .

[9]  K. Taylor,et al.  The Geoengineering Model Intercomparison Project (GeoMIP) , 2011 .

[10]  A simple model to account for regional inequalities in the effectiveness of solar radiation management , 2012, Climatic Change.

[11]  Daniel Heyen,et al.  Beyond calculation - Climate Engineering risks from a social sciences perspective , 2012 .

[12]  M. G. Morgan,et al.  Effectiveness of stratospheric solar-radiation management as a function of climate sensitivity , 2011, Nature Climate Change.

[13]  Ken Caldeira,et al.  Ecosystem Impacts of Geoengineering: A Review for Developing a Science Plan , 2011, AMBIO.

[14]  Cecilia M. Bitz,et al.  Time-Varying Climate Sensitivity from Regional Feedbacks , 2012 .

[15]  U. Lohmann,et al.  Title : Effects of stratospheric sulfate aerosol geoengineering on cirrus clouds , 2012 .

[16]  David Leedal,et al.  The Geoengineering Model Intercomparison Project (GeoMIP): a control perspective , 2012 .

[17]  C. Bitz,et al.  The Climate Response to Stratospheric Sulfate Injections and Implications for Addressing Climate Emergencies , 2012 .

[18]  Mark Lawrence,et al.  Solar irradiance reduction to counteract radiative forcing from a quadrupling of CO2: climate responses simulated by four earth system models , 2012 .

[19]  P. Rasch,et al.  Climate model response from the Geoengineering Model Intercomparison Project (GeoMIP) , 2013 .

[20]  Douglas G. MacMartin,et al.  Dynamics of the coupled human–climate system resulting from closed-loop control of solar geoengineering , 2014, Climate Dynamics.

[21]  Ken Caldeira,et al.  Management of trade-offs in geoengineering through optimal choice of non-uniform radiative forcing , 2013 .

[22]  Philip J. Rasch,et al.  Explicit feedback and the management of uncertainty in meeting climate objectives with solar geoengineering , 2014 .

[23]  Shingo Watanabe,et al.  Key factors governing uncertainty in the response to sunshade geoengineering from a comparison of the GeoMIP ensemble and a perturbed parameter ensemble , 2014 .

[24]  R. Cairns,et al.  The Security Implications of Geoengineering: Blame, Imposed Agreement and the Security of Critical Infrastructure , 2014 .

[25]  Shingo Watanabe,et al.  A multi-model assessment of regional climate disparities caused by solar geoengineering , 2014 .

[26]  Carol L. Silva,et al.  Geoengineering and Climate Change Polarization: Testing a Two-channel Model of Science Communication , 2015 .