See our new paper published on Monday. It is open access.
Xia, Lili, Peer J. Nowack, Simone Tilmes, and Alan Robock, 2017: Impacts
of stratospheric sulfate geoengineering on tropospheric ozone, /Atmos.
Chem. Phys./, *17*, 11913-11928, https://doi.org/10.5194/acp-17-11913-2017.
https://www.atmos-chem-phys.net/17/11913/2017/
*Abstract.* A range of solar radiation management (SRM) techniques has
been proposed to counter anthropogenic climate change. Here, we examine
the potential effects of stratospheric sulfate aerosols and solar
insolation reduction on tropospheric ozone and ozone at Earth's surface.
Ozone is a key air pollutant, which can produce respiratory diseases and
crop damage. Using a version of the Community Earth System Model from
the National Center for Atmospheric Research that includes comprehensive
tropospheric and stratospheric chemistry, we model both stratospheric
sulfur injection and solar irradiance reduction schemes, with the aim of
achieving equal levels of surface cooling relative to the Representative
Concentration Pathway 6.0 scenario. This allows us to compare the
impacts of sulfate aerosols and solar dimming on atmospheric ozone
concentrations. Despite nearly identical global mean surface
temperatures for the two SRM approaches, solar insolation reduction
increases global average surface ozone concentrations, while sulfate
injection decreases it. A fundamental difference between the two
geoengineering schemes is the importance of heterogeneous reactions in
the photochemical ozone balance with larger stratospheric sulfate
abundance, resulting in increased ozone depletion in mid- and high
latitudes. This reduces the net transport of stratospheric ozone into
the troposphere and thus is a key driver of the overall decrease in
surface ozone. At the same time, the change in stratospheric ozone
alters the tropospheric photochemical environment due to enhanced
ultraviolet radiation. A shared factor among both SRM scenarios is
decreased chemical ozone loss due to reduced tropospheric humidity.
Under insolation reduction, this is the dominant factor giving rise to
the global surface ozone increase. Regionally, both surface ozone
increases and decreases are found for both scenarios; that is, SRM would
affect regions of the world differently in terms of air pollution. In
conclusion, surface ozone and tropospheric chemistry would likely be
affected by SRM, but the overall effect is strongly dependent on the SRM
scheme. Due to the health and economic impacts of surface ozone, all
these impacts should be taken into account in evaluations of possible
consequences of SRM.
--
Alan
_________________________________________________________________________
Alan Robock, Distinguished Professor
Editor, Reviews of Geophysics
Department of Environmental Sciences Phone: +1-848-932-5751
Rutgers University Fax: +1-732-932-8644
14 College Farm Road E-mail: [email protected]
New Brunswick, NJ 08901-8551 USA http://envsci.rutgers.edu/~robock
☮ http://twitter.com/AlanRobock 2017 Nobel Peace Prize to ICAN!
Watch my 18 min TEDx talk at http://www.youtube.com/watch?v=qsrEk1oZ-54
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