Uncertainties linked to land-surface processes in climate change simulations |
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Authors: | J F Crossley J Polcher P M Cox N Gedney S Planton |
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Institution: | (1) Laboratoire de Météorologie Dynamique du C.N.R.S., Tour 25, 5eme étage, 4 pl. Jussieu, 75252 Paris, Cedex 05, France E-mail: Jan.Polcher@lmd.jussieu.fr, FR;(2) Hadley Centre, Meteorological Office, Bracknell, UK, GB;(3) Reading University, Reading, UK, GB;(4) Météo-France, Toulouse, France, FR |
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Abstract: | The impact of climate change on the hydrology of continental surfaces is critical for human activities but the response of
the surface to this perturbation may also affect the sensitivity of the climate. This complex feedback is simulated in general
circulation models (GCMs) used for climate change predictions by their land-surface schemes. The present study attempts to
quantify the uncertainty associated with these schemes and what impact it has on our confidence in the simulated climate anomalies.
Four GCMs, each coupled to two different land-surface schemes, are used to explore the spectrum of uncertainties. It is shown
that, in this sample, surface processes have a significant contribution to our ability to predict surface temperature changes
and perturbations of the hydrological cycle in an environment with doubled greenhouse gas concentration. The results reveal
that the uncertainty introduced by land-surface processes in the simulated climate is different from its impact on the sensitivity
of GCMs to climate change, indeed an alteration of the surface parametrization with little impact on model climate can affect
sensitivity significantly. This result leads us to believe that the validation of land-surface schemes should not be limited
to the current climate but should also cover their sensitivity to variations in climatic forcing.
Received: 24 June 1999 / Accepted: 20 April 2000 |
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