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| Titel |
Impact of geoengineering on cirrus clouds |
| VerfasserIn |
Ana Cirisan, Peter Spichtinger, Debra Weisenstein, Ulrike Lohmann, Heini Wernli, Thomas Peter |
| 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 |
250035221
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| Zusammenfassung |
| Inspite of the framework convention agreement, climate warming is still an actual and very
important issue society has to deal with. This has motivated some scientist to start thinking
about implementation of artificial methods that could change the climate and weather patterns
in order to stop or reverse the global warming effects. Nowadays, there is a consortium of
politicians, scientists and engineers interested in evaluating different geoengineering schemes
as a way to mitigate global warming, discount rates, and risk aversion (Polborn S. and
Tintelnot F., 2009).
The geoengineering proposal attracting the most attention and having considerably lower
expected deployment costs than conventional emissions abatement approaches (Nordhaus,
2007) is stratospheric aerosol injection. This method, proposed by Budyko (1977) and
Crutzen (2006), relies on the fact that large amounts of sulphur aerosols injected into the
lower stratosphere enhance the Earth’s albedo and lead to cooling of the globe. This
proposal is currently discussed in the climate community and possible side effects are
investigated. However, the investigations concentrate almost exclusively on the impact on
chemistry and stratospheric circulation, whereas the impact on cirrus clouds in the
underlying tropopause and upper troposphere region was not taken into account up to
now.
In this contribution we investigated the impact of artificially produced sulphate
aerosol concentrations, modeled with the AER 2D aerosol model (Weisenstein et al.,
2007), on the formation and evolution of cirrus clouds in the mid-latitudes. For
large injections of SO2 some sulphate aerosol particles grow to large sizes that
they can sediment to lower altitudes and eventually reach the troposphere, where
they can influence ice crystal formation. Investigations are carried out using a bulk
microphysical box model (Spichtinger and Gierens, 2009, Spichtinger and Cziczo, 2009),
concentrating on moderate constant updrafts with different background aerosol
mass and number concentrations in response to geoengineering measures. In order
to obtain qualitative and quantitative estimations of troposphere-stratosphere air
mixing (intrusions, tropopause folds etc.) trajectory studies are done using ECMWF
data.
The results of this conceptual study suggest that an enhancement of sulphuric acid in the
tropopause and upper troposphere region may impact the ice crystal number concentrations in
cirrus clouds formed via homogeneous nucleation. The global impact can not be estimated,
but on the local level, this could lead to change of cloud lifetime and thickness. It would
further influence the albedo and radiative properties of cirrus clouds, i.e. modifying the net
warming impact of cirrus clouds.
Budyko, M.I. (1977), Global Ecology. Mysl, Moscow, 327 pp. (in Russian).
Crutzen, P.J. (2006), Albedo enhancement by stratospheric sulfur injections: A
contribution to resolve a policy dilemma?, Climate Change, 77(3-4), 211–219.
Nordhaus, W.D. (2007), A Question of Balance: Economic Modeling of Global Warming,
Yale University Press, 2007.
Polborn, S. and Tintelnot, F. (2009), How Geoengineering May Encourage Carbon
Dioxide Abatement (June 2, 2009). Available at SSRN: http://ssrn.com/abstract=1413106
Spichtinger, P. and Gierens, K. (2009), Modelling of cirrus clouds – Part 1a: Model
description and validation, Atmos. Chem. Phys., 9, 685-706.
Spichtinger, P. and Cziczo, D. (2009), Impact of heterogeneous ice nuclei on
homogeneous freezing events, J. Geophys. Res., in revision.
Weisenstein, D.K., Penner, J.E., Herzog, M., and Liu, X., (2007), Global 2-D
intercomparison of sectional and modal aerosol modules, Atmos. Chem. Phys., 7(9),
2339–2355. |
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