Effects of Different Stratospheric SO2 Injection Altitudes on Stratospheric Chemistry and Dynamics. Issue 9 (3rd May 2018)

• Record Type: Journal Article
• Authors: Tilmes, Simone; Richter, Jadwiga H.; Mills, Michael J.; Kravitz, Ben; MacMartin, Douglas G.; Garcia, Rolando R.; Kinnison, Douglas E.; Lamarque, Jean‐Francois; Tribbia, Joseph; Vitt, Francis
• Is Part Of: Journal of geophysical research. Volume 123:Issue 9(2018)
• Page Start: 4654
• Page End: 4673
• Publication Date: 2018-05-03
• Subjects: geoengineering -- ozone hole -- SRM -- aerosol -- stratospheric dynamics and chemistry -- climate engineering; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/2017JD028146
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Strategically applied geoengineering is proposed to reduce some of the known side effects of stratospheric aerosol modifications. Specific climate goals could be reached depending on design choices of stratospheric sulfur injections by latitude, altitude, and magnitude. Here we explore in detail the stratospheric chemical and dynamical responses to injections at different altitudes using a fully coupled Earth System Model. Two different scenarios are explored that produce approximately the same global cooling of 2°C over the period 2042–2049, a high‐altitude injection case using 24 Tg SO2 /year at 30 hPa (≈25‐km altitude) and a low‐altitude injection case using 32 Tg SO2 /year injections at 70 hPa (between 19‐ and 20‐km altitude), with annual injections divided equally between 15°N and 15°S. Both cases result in a warming of the lower tropical stratosphere up to 10 and 15°C for the high‐ and low‐altitude injection case and in substantial increases of stratospheric water vapor of up to 2 and 4 ppm, respectively, compared to no geoengineering conditions. Polar column ozone in the Northern Hemisphere is reduced by up to 18% in March for the high‐altitude injection case and up to 8% for the low‐altitude injection case. However, for winter middle and high northern latitudes, low‐altitude injections result in greater column ozone values than without geoengineering. These changes are mostly driven by dynamics and advection. Antarctic column ozone in 2042–2049 does not recover from present‐day (2002–2009) values for both cases. Key Points: Very similar surface cooling can be achieved with stratospheric SO2 injections at 1 and 5 km above the tropopause (at 15°N and 15°S) The 33% more injection is required for the low‐altitude injection case, resulting in significantly stronger heating of the tropical stratosphere Chemical and dynamical changes explain differences in the column ozone response to SO2 injections between high‐ and low‐altitude injections