|The Regional Impacts of Climate Change|
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11.2.3. Projections of Future Climates: Regional Scenarios
The first detailed climate scenario for south and southeast Asia was developed by the Climate Impact Group (1992), as part of the Asian Development Bank's 1994 regional study on global environmental issues (including climate change); the methodology is outlined by Whetton (1994). Analyses were carried out using data obtained in experiments with four general circulation models (GCMs): the Canadian Climate Centre model (CCCJ1), the United Kingdom Meteorological Office model (UKMOH), the Geophysical Fluid Dynamics model (GFDLA), and the Australian CSIRO9 model. All of the experiments used an atmospheric model coupled to a simplified ocean model and were run to equilibrium conditions for present levels of greenhouse gases (GHGs) and for doubled CO2 levels.
Comparisons of the control simulation of the GCMs with present-day climatology included results for the region's surface temperature, mean sea-level pressure, and precipitation. The broad-scale observed patterns are well simulated, including the summer and winter monsoons. Results described by Suppiah (1994), based on the aforementioned models, indicated strengthening of the monsoon circulation and an increase in wet-season rainfall under enhanced greenhouse conditions-that is, an increase in summer rainfall in the southWest monsoon region and an increase in winter rainfall in the northeast monsoon region.
Temperature and rainfall scenarios are based on simulated changes averaged
over two broad seasons: the southWest monsoon and the northeast monsoon. Temperature
scenarios for Tropical Asia reported by Whetton (1994) and the Climate Impact
Group (1992) suggest that temperature would increase throughout most of the
region, although the amount of warming is projected to be less than the global
average. Moreover, results presented in Table 11-3
indicate that there may be differences within the region, depending on proximity
to the sea. Thus, warming is projected to be least in the islands and coastal
areas throughout Indonesia, the Philippines, and coastal south Asia and Indo-China
and greatest in inland continental areas of south Asia and Indo-China-except
from June to August in south Asia, where reduced warming could occur.
Systematic increases in average rainfall intensity are a common feature in simulated daily rainfall experiments, along with associated increases in the projected frequency of heavy rainfall events. Whetton et al. (1994) conclude that there is reason for higher confidence in increasing rainfall intensity in south and southeast Asia under enhanced greenhouse conditions than in increases or decreases in total rainfall in particular regions.
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