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| Titel |
Do GCMs predict the climate ... or macroweather? |
| VerfasserIn |
S. Lovejoy, D. Schertzer, D. Varon |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
2190-4979
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| Digitales Dokument |
URL |
| Erschienen |
In: Earth System Dynamics ; 4, no. 2 ; Nr. 4, no. 2 (2013-11-28), S.439-454 |
| Datensatznummer |
250084962
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| Publikation (Nr.) |
 copernicus.org/esd-4-439-2013.pdf |
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| Zusammenfassung |
| We are used to the weather–climate dichotomy, yet the great majority of
the spectral variance of atmospheric fields is in the continuous
"background" and this defines instead a trichotomy with a "macroweather"
regime in the intermediate range from ≈10 days to 10–30 yr
(≈100 yr in the preindustrial period). In the weather,
macroweather and climate regimes, exponents characterize the type of
variability over the entire regime and it is natural to identify them with
qualitatively different synergies of nonlinear dynamical mechanisms that
repeat scale after scale. Since climate models are essentially
meteorological models (although with extra couplings) it is thus important
to determine whether they currently model all three regimes. Using last
millennium simulations from four GCMs (global circulation models), we show that control runs only
reproduce macroweather. When various (reconstructed) climate forcings are
included, in the recent (industrial) period they show global fluctuations
strongly increasing at scales > ≈10–30 yr, which is quite
close to the observations. However, in the preindustrial period we find
that the multicentennial variabilities are too weak and by analysing the
scale dependence of solar and volcanic forcings, we argue that these forcings are
unlikely to be sufficiently strong to account for the multicentennial and
longer-scale temperature variability. A likely explanation is that the
models lack important slow "climate" processes such as land ice or various
biogeochemical processes. |
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