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| Titel |
Radiative forcings for 28 potential Archean greenhouse gases |
| VerfasserIn |
B. Byrne, C. Goldblatt |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 10, no. 5 ; Nr. 10, no. 5 (2014-10-01), S.1779-1801 |
| Datensatznummer |
250117055
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| Publikation (Nr.) |
 copernicus.org/cp-10-1779-2014.pdf |
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| Zusammenfassung |
| Despite reduced insolation in the late Archean, evidence suggests a~warm
climate which was likely sustained by a stronger greenhouse effect, the
so-called faint young sun problem (FYSP). CO2 and CH4 are
generally thought to be the mainstays of this enhanced greenhouse, though
many other gases have been proposed. We present high accuracy radiative
forcings for CO2, CH4, and 26 other gases, performing the
radiative transfer calculations at line-by-line resolution and using HITRAN
2012 line data for background pressures of 0.5, 1, and 2 bar of
atmospheric N2. For CO2 to resolve the FYSP alone at
2.8 Gyr BP (80% of present solar luminosity), 0.32 bar is
needed with 0.5 bar of atmospheric N2, 0.20 bar
with 1 bar of atmospheric N2, or 0.11 bar with
2 bar of atmospheric N2. For CH4, we find that
near-infrared absorption is much stronger than previously thought, arising
from updates to the HITRAN database. CH4 radiative forcing peaks at
10.3, 9, or 8.3 W m−2 for background pressures of 0.5, 1, or
2 bar, likely limiting the utility of CH4 for warming the
Archean. For the other 26 HITRAN gases, radiative forcings of up to a few to
10 W m−2 are obtained from concentrations of 0.1–1 ppmv for
many gases. For the 20 strongest gases, we calculate the reduction in
radiative forcing due to overlap. We also tabulate the modern sources, sinks,
concentrations, and lifetimes of these gases and summaries the literature on
Archean sources and concentrations. We recommend the forcings provided here
be used both as a first reference for which gases are likely good greenhouse
gases, and as a standard set of calculations for validation of radiative
forcing calculations for the Archean. |
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