Agriculture Reference
In-Depth Information
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The “expanding Sahara” hypothesis paved the way to the description of a
biogeophysical feedback mechanism (Charney et al., 1975), proven later by
using the numerical climate model of the Goddard Institute for Space Stud-
ies (Hansen et al., 1988). Various research programs are being undertaken
to study the weather and climate of arid, semiarid, subhumid and other
desert-prone areas with a view to predict long-term trends in the general
circulation, different rain-producing atmospheric disturbances, and mete-
orological droughts using statistical and dynamic methods.
Human-induced changes in dryland surface conditions and atmospheric
composition can certainly have an impact on local and regional climate
conditions because they directly affect the energy budget of the surface and
the overlying atmospheric column. These changes to the energy balance
have been simulated in many numerical modeling studies covering almost
all dryland areas of the world. The outcomes of these studies underscore the
need to improve our knowledge of the climate-desertification relationship
and, at the same time, call for improvements in the quantity and quality of
the data available for further simulations. Accordingly, the WMO World
Climate Research Programme (WCRP) launched the Global Energy and
Water Cycle Experiment (GEWEX;
www.gewex.org
) to study the atmo-
spheric and thermodynamic processes that determine the global hydrolog-
ical cycle and energy budget and their adjustments to global changes, such
as an increase in greenhouse gases. Many of the fundamental issues associ-
ated with interactions of desertification and climate are receiving attention
in the GEWEX objectives.
Empirical studies that had begun with the analysis of historical records
received a considerable thrust from improvements in remote-sensing ob-
servation and measurement technologies. The International Satellite Land
Surface Climatology Project (
www.gewex.org/islscp.html)
has substan-
tially improved the amount and quality of data available for use in em-
pirical and numerical modeling studies.
WMO is strengthening and intensifying the research on the interactions
between climate and desertification. The urgent need to predict interannual
climate variations is impelled by the socioeconomic upheavals that have oc-
curred, especially in Africa, over the past few decades. Statistical forecasts
of seasonal rainfall up to 3 months in advance are currently being made,
but through a coordinated research effort significant improvements in reli-
ability and lead-time could be expected (Cane and Arkin, 2000). Equipped
with an improved understanding of the physical mechanisms that govern
climate and with more reliable predictive models, countries would be in
a far better position to predict the onset of drought and hence mitigate
its devastating consequences. Strategic plans could then be developed for
capitalizing on the extended predictive capabilities and for converting the
forecasts to management decisions that will optimize the use of existing
resources.
WMO improves climate prediction capability through the Climate Vari-
ability Project (CLIVAR;
www.clivar.org)
of the WCRP. The prediction of
El Niño and associated impacts are becoming possible, with reasonable
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