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| Titel |
A new method to diagnose the contribution of anthropogenic activities to temperature: temperature tagging |
| VerfasserIn |
V. Grewe |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 6, no. 2 ; Nr. 6, no. 2 (2013-03-26), S.417-427 |
| Datensatznummer |
250017799
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| Publikation (Nr.) |
 copernicus.org/gmd-6-417-2013.pdf |
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| Zusammenfassung |
| This study presents a new methodology, called temperature tagging.
It keeps track of the contributions of individual processes to
temperature within a climate model simulation. As a first step and
as a test bed, a simple box climate model is regarded. The model
consists of an atmosphere, which absorbs and emits radiation, and of
a surface, which reflects, absorbs and emits radiation. The tagging
methodology is used to investigate the impact of the atmosphere on
surface temperature. Four processes are investigated in more
detail and their contribution to the surface temperature quantified:
(i) shortwave influx and shortwave atmospheric absorption ("sw"),
(ii) longwave atmospheric absorption due to non-CO2
greenhouse gases ("nC"), (iii) due to a base case CO2
concentration ("bC"), and (iv) due to an enhanced CO2
concentration ("eC"). The differential equation for the
temperature in the box climate model is decomposed into four
equations for the tagged temperatures. This method is applied to
investigate the contribution of longwave absorption to the surface
temperature (greenhouse effect), which is calculated to be
68 K. This estimate contrasts an alternative calculation of
the greenhouse effect of slightly more than 30 K based on
the difference of the surface temperature with and without an
atmosphere. The difference of the two estimates is due to
a shortwave cooling effect and a reduced contribution of the
shortwave to the total downward flux: the shortwave absorption of the
atmosphere results in a reduced net shortwave flux at the surface of
192 W m−2, leading to a cooling of the surface by
14 K. Introducing an atmosphere results in a downward
longwave flux at the surface due to atmospheric absorption of
189 W m−2, which roughly equals the net shortwave flux
of 192 W m−2. This longwave flux is a result of both
the radiation due to atmospheric temperatures and its longwave
absorption. Hence the longwave absorption roughly accounts for
91 W m−2 out of a total of 381 W m−2
(roughly 25%) and therefore accounts for a temperature change of
68 K. In a second experiment, the CO2 concentration
is doubled, which leads to an increase in surface temperature of
1.2 K, resulting from a temperature increase due to
CO2 of 1.9 K, due to non-CO2 greenhouse
gases of 0.6 K and a cooling of 1.3 K due to
a reduced importance of the solar heating for the surface and
atmospheric temperatures. These two experiments show the feasibility
of temperature tagging and its potential as a diagnostic for climate
simulations. |
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