Geoscience Reference
In-Depth Information
limitations of GCMs in predicting climate change. The most
significant limitations include
1. Poor spatial resolution
2. Inadequate coupling of atmospheric and oceanic processes
3. Poor simulation of cloud processes
4. Inadequate representation of the biosphere and its feedback
There are now many different models being used to simulate
climate change, because several modelling groups constantly
revise the GCMs. In general, GCMs can at best be used to sug-
gest the likely direction and rate of change, because they still have
significant inherent limitations in simulating current climate.
The rate of increase of global mean surface temperature
is predicted to be around 0.3°C before the end of the century.
Regional climate changes are different from the global mean. It
is predicted that surface air will warm faster over land than over
oceans and that the warming is expected to be 50-100% greater
than the global mean in high northern latitudes in winter. There
is increased precipitation in the order of 5-10% in middle and
high latitude continents (35-55°N) in winter. The global mean
sea level is expected to rise about 6 cm per decade on average
over the next century mainly due to the thermal expansion of
the oceans and the melting of some land ice. A sea level rise of
about 65 cm is predicted by the end of the next century.
Although GCM predictions are not ideal for agricultural
impact analysis, they serve as a suitable benchmark for our global
economic analysis directed at evaluating general directions and
elative magnitudes of change, In particular, the GCM predictions
suggest broad geographical zones across which climate change
may affect agriculture. Increased precipitation and warming in
the high northern latitudes could enhance agricultural production
potential in the northern regions of the erstwhile Soviet Union,
Canada and northern Europe. Drying in the interior of conti-
nents in the northern middle latitudes combined with warming
could lead to negative crop and livestock effects in the United
States and Western Europe and the most agriculturally produc-
tive regions of Canada. Other northern middle latitude regions,
including South-East Asia could suffer from coastal inundation.
There are exceptions to the broadly generalised climate
patterns sketched by the IPCC. While China falls within the
category of northern middle latitude countries, climate mod-
els suggest crop production potential could increase. Regions
of agricultural importance in the southern middle latitudes
include Argentina and Australia. Projections show a wetter
