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Can we test geoengineering?

MacMynowski, Douglas G. and Keith, David W. and Caldeira, Ken and Shin, Ho-Jeong (2011) Can we test geoengineering? Energy and Environmental Science, 4 (12). pp. 5044-5052. ISSN 1754-5692.

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Solar radiation management (SRM), a form of geoengineering, might be used to offset some fraction of the anthropogenic radiative forcing of climate as a means to reduce climate change, but the risks and effectiveness of SRM are uncertain. We examine the possibility of testing SRM through sub-scale deployment as a means to test models of climate response to SRM and explore risks prior to full-scale implementation. Contrary to some claims, this could provide meaningful tests of the climate's response to SRM within a decade. We use idealized simulations with the HadCM3L general circulation model (GCM) to estimate the response to SRM and signal-to-noise ratio for global-scale SRM forcing tests, and quantify the trade-offs between duration and intensity of the test and it's ability to make quantitative measurements of the climate's response to SRM forcing. The response at long time-scales would need to be extrapolated from results measured by a short-term test; this can help reduce the uncertainty associated with relatively rapid climate feedbacks, but uncertainties that only manifest at long time-scales can never be resolved by such a test. With this important caveat, the transient climate response may be bounded with 90% confidence to be no more than 1.5 °C higher than it's estimated value, in a single decade test that used roughly 1/10th the radiative forcing perturbation of a CO_2-doubling. However, tests could require several decades or longer to obtain accurate response estimates, particularly to understand the response of regional hydrological fields which are critical uncertainties. Some fields, like precipitation over land, have as large a response to short period forcing as to slowly-varying changes. This implies that the ratio of the hydrological to the temperature response that results from a sustained SRM deployment will differ from that of either a short-duration test or that which has been observed to result from large volcanic eruptions.

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URLURL TypeDescription DOIArticle
MacMynowski, Douglas G.0000-0003-1987-9417
Additional Information:© 2011 The Royal Society of Chemistry. Received 3rd March 2011, Accepted 19th September 2011. First published on the web 20 Oct 2011. NCEP Reanalysis data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their Web site at
Issue or Number:12
Record Number:CaltechAUTHORS:20120104-093848557
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:28639
Deposited By: Tony Diaz
Deposited On:06 Jan 2012 21:42
Last Modified:03 Oct 2019 03:34

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