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| Titel |
HESS Opinions "Should we apply bias correction to global and regional climate model data?" |
| VerfasserIn |
U. Ehret, E. Zehe, V. Wulfmeyer, K. Warrach-Sagi, J. Liebert |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 16, no. 9 ; Nr. 16, no. 9 (2012-09-21), S.3391-3404 |
| Datensatznummer |
250013478
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| Publikation (Nr.) |
 copernicus.org/hess-16-3391-2012.pdf |
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| Zusammenfassung |
| Despite considerable progress in recent years, output of both global and
regional circulation models is still afflicted with biases to a degree that
precludes its direct use, especially in climate change impact studies. This
is well known, and to overcome this problem, bias correction (BC; i.e. the
correction of model output towards observations in a post-processing step)
has now become a standard procedure in climate change impact studies. In
this paper we argue that BC is currently often used in an invalid way: it is
added to the GCM/RCM model chain without sufficient proof that the
consistency of the latter (i.e. the agreement between model dynamics/model
output and our judgement) as well as the generality of its applicability
increases. BC methods often impair the advantages of circulation models by
altering spatiotemporal field consistency, relations among variables and by
violating conservation principles. Currently used BC methods largely neglect
feedback mechanisms, and it is unclear whether they are time-invariant under
climate change conditions. Applying BC increases agreement of climate model
output with observations in hindcasts and hence narrows the uncertainty
range of simulations and predictions without, however, providing a
satisfactory physical justification. This is in most cases not transparent
to the end user. We argue that this hides rather than reduces uncertainty,
which may lead to avoidable forejudging of end users and decision makers.
We present here a brief overview of state-of-the-art bias correction
methods, discuss the related assumptions and implications, draw conclusions
on the validity of bias correction and propose ways to cope with biased
output of circulation models in the short term and how to reduce the bias in
the long term. The most promising strategy for improved future global and
regional circulation model simulations is the increase in model resolution
to the convection-permitting scale in combination with ensemble predictions
based on sophisticated approaches for ensemble perturbation.
With this article, we advocate communicating the entire uncertainty range
associated with climate change predictions openly and hope to stimulate a
lively discussion on bias correction among the atmospheric and hydrological
community and end users of climate change impact studies. |
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