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Published December 16, 2017 | Supplemental Material + Published
Journal Article Open

First Simulations of Designing Stratospheric Sulfate Aerosol Geoengineering to Meet Multiple Simultaneous Climate Objectives

Abstract

We describe the first simulations of stratospheric sulfate aerosol geoengineering using multiple injection locations to meet multiple simultaneous surface temperature objectives. Simulations were performed using CESM1(WACCM), a coupled atmosphere-ocean general circulation model with fully interactive stratospheric chemistry, dynamics (including an internally generated quasi-biennial oscillation), and a sophisticated treatment of sulfate aerosol formation, microphysical growth, and deposition. The objectives are defined as maintaining three temperature features at their 2020 levels against a background of the RCP8.5 scenario over the period 2020–2099. These objectives are met using a feedback mechanism in which the rate of sulfur dioxide injection at each of the four locations is adjusted independently every year of simulation. Even in the presence of uncertainties, nonlinearities, and variability, the objectives are met, predominantly by SO_2 injection at 30°N and 30°S. By the last year of simulation, the feedback algorithm calls for a total injection rate of 51 Tg SO_2 per year. The injections are not in the tropics, which results in a greater degree of linearity of the surface climate response with injection amount than has been found in many previous studies using injection at the equator. Because the objectives are defined in terms of annual mean temperature, the required geongineering results in "overcooling" during summer and "undercooling" during winter. The hydrological cycle is also suppressed as compared to the reference values corresponding to the year 2020. The demonstration we describe in this study is an important step toward understanding what geoengineering can do and what it cannot do.

Additional Information

© 2017. American Geophysical Union. Received 30 MAR 2017. Accepted 12 OCT 2017. Accepted article online 6 NOV 2017. Published online 7 DEC 2017. Special Section: Simulations of Stratospheric Sulfate Aerosol Geoengineering with the Whole Atmosphere Community Climate Model (WACCM) This article is a companion to Mills et al. (2017), https://doi.org/10.1002/2017JD027006; Richter et al. (2017), https://doi.org/10.1002/2017JD026912; MacMartin et al. (2017), https://doi.org/10.1002/2017JD026868; and Tilmes et al. (2017), https://doi.org/10.1002/2017JD026888 This research was developed with funding from the Defense Advanced Research Projects Agency (DARPA). The views, opinions, and/or findings expressed are those of the authors and should not be interpreted as representing the official views or policies of the Department of Defense or the U.S. Government. The Pacific Northwest National Laboratory is operated for the U.S. Department of Energy by Battelle Memorial Institute under contract DE-AC05-76RL01830. Simulations were carried out on the Yellowstone high-performance computer platform (Computational and Informational Systems Laboratory 2012). The CESM project is supported by the National Science Foundation and the Office of Science (BER) of the U.S. Department of Energy. The National Center for Atmospheric Research is funded by the National Science Foundation. Model output for the 10 year system identification simulations (Tilmes et al., 2017) is available on the Earth System Grid at https://doi.org/10.5065/D6X63KMM.

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Published - Kravitz_et_al-2017-Journal_of_Geophysical_Research__Atmospheres.pdf

Supplemental Material - jgrd54215-sup-0001-supinfo.pdf_v=1_s=d78ce52f57adcc9c2424717c337c1e8061395fbf

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Additional details

Created:
August 21, 2023
Modified:
October 23, 2023