Jahresbericht 08 - PMOD/WRC

With CCM SOCOL v2.0 we have simulated the evolution
of the climate, chemistry and ozone during 20th
century. The analysis of the land surface temperature
changes revealed that the contribution of solar variability
to climate warming can reach ~50 % in some regions
(e.g., Siberia, Scandinavia, Central USA and
Southern Canada).
We have carried out a 9-member 100-year long transient
ensemble simulation with CCM SOCOL spanning the entire
20th century driven by the prescribed time evolution of
the sea surface temperature, sea ice distribution, volcanic
aerosols, solar spectral irradiance, greenhouse gases,
ozone depleting substances, sources of CO and NOx, land
use, and quasi-biannual oscillation. The model set-up and
some results from this experiment were presented by Fischer
et al. (2008). To elucidate the role of changes in solar
activity we have also performed one run without solar irradiance
variability.
Figure 1 illustrates the annual mean land surface temperature
changes calculated as the difference between mean
values over the time periods 1985-1999 and 1901-1915.
The increase of the sea surface temperature is prescribed
from observations, so it is consistent with observations.
The model also simulates the observed warming over land,
which maximizes over high-latitudes and Saudi Arabia.
To estimate the contribution of the solar irradiance variability
we compared temperature changes during 20th century
shown in Figure 1 with the same temperature changes
obtained from the model run carried out with fixed solar
spectral irradiance. The contribution of solar irradiance variability
is shown in Figure 2. The solar spectral irradiance
contribution is rather small over the ocean, because the
ocean temperature was prescribed in both experiments.
Over land the contribution of solar irradiance variability is
noticeable over some geographical locations. Its magnitude
can reach 0.6 K over Siberia, Scandinavia, Central
USA and Canada. Cooling due to solar irradiance variability
is observed over Northern Canada, China and Northern
Africa.
Scientific Research Activities 21
The Response of the Land Surface Temperature to the Solar Irradiance Variability
Eugene Rozanov, Tatiana Egorova, and Werner Schmutz
in collaboration with Andreas Fischer and Stefan Brönnimann IAC ETH, Zurich
References: Fischer A., Schraner M., Rozanov E., Kenzelmann P.,
Schnadt Poberaj C., Brunner D., Lustenberger A.,
Luo B.P., Bodeker G.E., Egorova T., Schmutz W.,
Peter T., Brönnimann S., Interannual-to-decadal variability
of the stratosphere during the 20th century:
ensemble simulations with a chemistry-climate model,
Atmos. Chem. Phys., 8, 7755-7777, 2008.
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Figure 1. Changes of the annual mean surface air temperature between
two time periods: 1985-1999 and 1901-1915.
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Figure 2. Contribution of solar irradiance variability to changes in the annual
mean surface air temperature between two time periods: 1985-1999
and 1901-1915.