Impacts of stratospheric sulfate geoengineering on tropospheric ozone
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 po...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-10-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/17/11913/2017/acp-17-11913-2017.pdf |
| Summary: | 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. |
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| ISSN: | 1680-7316 1680-7324 |