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| Titel |
Moist Greenhouse states with solar and CO2-induced forcing |
| VerfasserIn |
Max Popp, Hauke Schmidt, Jochem Marotzke |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250123944
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| Publikation (Nr.) |
 EGU/EGU2016-3288.pdf |
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| Zusammenfassung |
| Water-rich planets such as Earth are expected to become eventually uninhabitable, because
liquid water does not remain stable at the surface as surface temperatures increase with the
solar luminosity over time. It is conceivable that a large increase in atmospheric
greenhouse-gas concentrations could also destroy the habitability of water-rich planets, but
previous studies could not clearly establish this. Here we use for the first time a
state-of-the-art atmospheric general circulation model, namely a modified version of
ECHAM6, to compare the potential of both solar and CO2-induced forcing to render a
water-rich planet uninhabitable.
We find that CO2-induced forcing as readily destabilizes a present-day Earth-like
climate as does solar forcing. This climate instability is caused by a positive cloud
feedback, which is in turn caused by the weakening large-scale circulation with
increasing surface temperature. The climate does not run away, but instead attains a
new steady state with global-mean sea-surface temperatures above 330 K. The
upper atmosphere is considerably moister in this warm steady state than in the
reference climate. The upper-atmospheric mixing ratio of water exceeds the so-called
Moist-Greenhouse limit, which implies that the planet would be subject to substantial loss of
water to space. For either a certain range of elevated CO2 concentrations or solar
irradiation, we find both cold and warm equilibrium states. Therefore the transition to
the warm state may not simply be reversed by removing the additional forcing. |
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