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| Titel |
Another look at climate sensitivity |
| VerfasserIn |
I. Zaliapin, M. Ghil |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 17, no. 2 ; Nr. 17, no. 2 (2010-03-17), S.113-122 |
| Datensatznummer |
250013657
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| Publikation (Nr.) |
 copernicus.org/npg-17-113-2010.pdf |
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| Zusammenfassung |
| We revisit a recent claim
that the Earth's climate system is characterized by sensitive dependence
to parameters; in particular, that the system exhibits an asymmetric,
large-amplitude response to normally distributed feedback forcing.
Such a response would imply irreducible uncertainty in climate change
predictions and thus have notable implications for climate science and
climate-related policy making.
We show that equilibrium climate sensitivity in all generality does
not support such an intrinsic indeterminacy; the latter appears
only in essentially linear systems.
The main flaw in the analysis that led to this claim is inappropriate
linearization of an intrinsically nonlinear model; there is no room
for physical interpretations or policy conclusions based on this
mathematical error. Sensitive dependence nonetheless does exist
in the climate system, as well as in climate models – albeit in a very
different sense from the one claimed in the linear work under scrutiny – and
we illustrate it using
a classical energy balance model (EBM) with nonlinear feedbacks.
EBMs exhibit two saddle-node bifurcations, more recently called "tipping points,"
which give rise to three distinct steady-state climates, two of which are
stable. Such bistable behavior is, furthermore,
supported by results from more realistic, nonequilibrium climate models.
In a truly nonlinear setting, indeterminacy in the size of the response
is observed only in the vicinity of tipping points.
We show, in fact, that small disturbances cannot result in a large-amplitude
response, unless the system is at or near such a point.
We discuss briefly how the distance to the bifurcation may be related to
the strength of Earth's ice-albedo feedback. |
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