This following paper is published in ACP today. The main focus is on the
hydrological impacts of varying the latitudinal distribution of a FIXED
amount of aerosols. Sensitivity of simulated climate to latitudinal
distribution of solar insolation reduction in solar radiation management
A. Modak and G. Bala
Divecha Centre for Climate Change {&} Centre for Atmospheric and Oceanic
Sciences, Indian Institute of Science, Bangalore, 560 012, India
Abstract. Solar radiation management (SRM) geoengineering has been proposed
as a potential option to counteract climate change. We perform a set of
idealized geoengineering simulations using Community Atmosphere Model
version 3.1 developed at the National Center for Atmospheric Research to
investigate the global hydrological implications of varying the latitudinal
distribution of solar insolation reduction in SRM methods. To reduce the
solar insolation we have prescribed sulfate aerosols in the stratosphere.
The radiative forcing in the geoengineering simulations is the net forcing
from a doubling of CO2 and the prescribed stratospheric aerosols. We find
that for a fixed total mass of sulfate aerosols (12.6 Mt of SO4), relative
to a uniform distribution which nearly offsets changes in global mean
temperature from a doubling of CO2, global mean radiative forcing is larger
when aerosol concentration is maximum at the poles leading to a warmer
global mean climate and consequently an intensified hydrological cycle.
Opposite changes are simulated when aerosol concentration is maximized in
the tropics. We obtain a range of 1 K in global mean temperature and 3% in
precipitation changes by varying the distribution pattern in our
simulations: this range is about 50% of the climate change from a doubling
of CO2. Hence, our study demonstrates that a range of global mean climate
states, determined by the global mean radiative forcing, are possible for a
fixed total amount of aerosols but with differing latitudinal distribution.
However, it is important to note that this is an idealized study and thus
not all important realistic climate processes are modeled.
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Best wishes,
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G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India
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