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| Titel |
Optimizing stratospheric sulfur geoengineering by seasonally changing sulfur injections |
| VerfasserIn |
Anton Laakso, Antti-Ilari Partanen, Harri Kokkola, Kari Lehtinen, Hannele Korhonen |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250110245
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| Publikation (Nr.) |
 EGU/EGU2015-10223.pdf |
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| Zusammenfassung |
| Solar radiation management (SRM) by stratospheric sulfur injection has been shown to have
potential in counteracting global warming if reducing of greenhouse gases has not been
achieved fast enough and if climate warming will continue. Injecting large amounts of sulfate
particles to the stratosphere would increase the reflectivity of the atmosphere and less
sunlight would reach the surface. However, the effectivity (per injected sulphur mass unit) of
this kind of geoengineering would decrease when amount of injected sulfur is increased.
When sulfur concentration increases, stratospheric particles would grow to larger sizes which
have larger gravitational settling velocity and which do not reflect radiation as efficiently as
smaller particles. In many previous studies, sulfur has been assumed to be injected along the
equator where yearly mean solar intensity is the highest and from where sulfur
is spread equally to both hemispheres. However, the solar intensity will change
locally during the year and sulfate has been assumed to be injected and spread to the
hemisphere also during winter time, when the solar intensity is low. Thus sulfate
injection could be expected to be more effective, if sulfur injection area is changed
seasonally.
Here we study effects of the different SRM injection scenarios by using two versions of
the MPI climate models. First, aerosol spatial and temporal distributions as well as the
resulting radiative properties from the SRM are defined by using the global aerosol-climate
model ECHAM6.1-HAM2.2-SALSA. After that, the global and regional climate effects from
different injection scenarios are predicted by using the Max Planck Institute’s Earth System
Model (MPI-ESM).
We carried out simulations, where 8 Tg of sulfur is injected as SO2 to the stratosphere at
height of 20-22 km in an area ranging over a 20 degree wide latitude band. Results show that
changing the sulfur injection area seasonally would lead to similar global mean shortwave
radiative forcing (-4.41 W/m2 at top of atmosphere) as if sulfur is injected only to the equator
(-4.40 W/m2). However zonal mean distribution would be different and forcing is
concentrated relatively more to the midlatitudes and less to the equator. Cooling effect from
the geoengineering and warming effect from the increased greenhouse gas has been
shown in many studies to lead to cooling in the equator and warming in the poles
compared the preindustrial conditions. Changing the injection area seasonally might
prevent this from happening and lead globally to more homogeneous temperature
change. |
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