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| Titel |
Efficient formation of stratospheric aerosol for geoengineering though emission of low-volatility vapours in an aircraft plume |
| VerfasserIn |
Jeffrey Pierce, Debra Weisenstein, David Keith |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250042607
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| Zusammenfassung |
| Previous research that has explored the impacts of geoengineered stratospheric
sulfate aerosol on climate and atmospheric chemistry has assumed that sulfur will be
injected into the stratosphere as SO2. SO2, having a lifetime of about a month in the
stratosphere, will be quite dispersed when it reacts with OH to form low-volatility
H2SO4. As found by Heckendorn et al. (2009), much of the H2SO4 mass produced in
geoengineering scenarios will go into increasing the size of existing aerosols, thus reducing
aerosol lifetime and mass scattering efficiency. The overall effect is that continuous
injection of SO2 may be surprisingly ineffective; the analysis showed, for example,
that a 10 Mt-S/yr injection rate produces a radiative forcing of only ~1.7 Wm-2,
whereas previous calculations with fixed particle size predicted that 10 Mt-S/yr
would produce a radiative forcing greater than 7 Wm-2. In this talk we explore an
alternative method of stratospheric sulfate aerosol geoengineering: the direct emission of
H2SO4 (or SO3) vapors. These vapors may be emitted from an aircraft by either
boiling liquid H2SO4 or burning sulfur in the presence of a vanadium catalyst. We
model the aerosol microphysics with an aircraft plume model coupled to a global
stratospheric aerosol model. We find that the emission of H2SO4 yields a much
narrower aerosol size distribution than emission of SO2, thus yielding a 60-70% larger
aerosol burden and 100% larger shortwave RF cooling in 5 MT S/yr cases. Because
aerosol formation in an aircraft plume is dominated by homogeneous nucleation
and fast condensation, the method is relatively insensitive the pre-existing aerosol
distributions. For a given radiative forcing, less S injection is necessary through H2SO4
emissions, however, the total mass necessary to be lifted to the stratosphere depends on
the injection method (e.g. boiling of H2SO4 versus combustion of S). Many of
the negative unintended consequences of H2SO4 injection (eg. ozone depletion,
effects on hydrological) will generally be similar to SO2; however, H2SO4 injection
would likely lead to less stratospheric warming from longwave absorption and
less sulfate deposition. This method of the injection of low-volatility vapors to
form aerosols is not limited to H2SO4, and materials could be tested for desired
properties (e.g. low toxicity, high SW scattering efficiency, low LW absorption
efficiency).
Heckendorn, P., et al., Env. Res. Let., 4 (2009) 045108 |
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