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The land surface is a key component of climate models. It controls the partitioning of available energy at the surface
between sensible and latent heat, and it controls the partitioning of available water between evaporation and runoff.
The land surface is also the location of the terrestrial carbon sink. Evidence is increasing that the influence of the land
surface is significant on climate and that changes in the land surface can influence regional- to global-scale climate on
time scales from days to millennia. Further, there is now a suggestion that the terrestrial carbon sink may decrease as
global temperatures increase as a consequence of rising CO2 levels. This paper provides the theoretical background that
explains why the land surface should play a central role in climate. It also provides evidence, sourced from climate
model experiments, that the land surface is of central importance. This paper then reviews the development of land
surface models designed for climate models from the early, very simple models through to recent efforts, which include
a coupling of biophysical processes to represent carbon exchange. It is pointed out that significant problems remain to be
addressed, including the difficulties in parameterizing hydrological processes, root processes, sub-grid-scale heterogeneity
and biogeochemical cycles. It is argued that continued development of land surface models requires more multidisciplinary
efforts by scientists with a wide range of skills. However, it is also argued that the framework is now in place within
the international community to build and maintain the latest generation of land surface models. Further, there should be
considerable optimism that consolidating the recent rapid advances in land surface modelling will enhance our capability
to simulate the impacts of land-cover change and the impacts of increasing CO2 on the global and regional environment.
Copyright 2003 Royal Meteorological Society.
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