11.4. Integrated Assessment of Potential Vulnerabilities and Impacts
Individual countries, regions, resources, sectors, and systems will be affected
by climate change not in isolation but in interaction with one another. The
direct effects of climate change to which this chapter alludes, such as changes
in rice crop yields and inundation of coastal areas, will have further indirect
effects.
Integration of impacts and adaptations to climate change can take many forms.
Several different approaches can be considered for Tropical Asia, including
the following:
- Country-Specific Studies-These studies have attempted to summarize
salient aspects of vulnerability, impacts, and adaptations, generally in a
qualitative manner. Some simple examples for India, Indonesia, Malaysia, and
Thailand are given in Section 6.5 of the Working Group III contribution to
the SAR (IPCC, 1996) and in ADB (1994a, 1994b). In these and other national
studies, the conclusions usually are strongly thematic or sector-based.
- Geographical Integration-Linkages between different functional regions
are difficult to investigate although, at a conceptual level, they are readily
acknowledged. For example, drainage basins can provide functional links between
climate change impacts in headwaters and the downstream areas they affect;
at the same time, however, downstream areas also may be responding to locally
specific climate change impacts. Some simple examples have been described
in this chapter (e.g., Section 11.3.3.3). Functional
adaptations-such as through total river catchment analyses or integrated coastal
management-are extraordinarily difficult to implement because of jurisdictional
sensitivities, even though conceptual and methodological hurdles may be relatively
easy to overcome.
- Sectoral and Trade Integration-There have been a number of attempts
to integrate the various components of food supply (agriculture) in Tropical
Asia, generally with simplified production change models in response to changes
in environmental conditions (e.g,. temperature or precipitation and their
derivatives, such as length of growing season and time of fruiting), some
with yield adaptations and some without. These results are then integrated
into an international trade-conditions model, and estimates of net economic
welfare impacts are calculated. Reilly et al. (1993) have done this for Tropical
Asia using three GCMs and 2xCO2 equilibrium scenarios.
- Comprehensive Monetary Estimates-Another way of integrating the range
of potential impacts of climate change is to derive a comprehensive monetary
estimate, which adds all of a country's impacts, expressed in their dollar
value. Expressing damage to marketed goods and services (e.g., land lost to
sea-level rise, energy savings in winter) in monetary terms is more or less
straightforward because the price is known. Expressing damage to nonmarketed
goods and services (e.g., wetland loss, mortality changes) in monetary terms
can be done either through examining market transactions where such goods
or services are implicitly traded (e.g., tourism, where landscape beauty is
valued) or through interviewing people to determine their preferences (i.e.,
their willingness to pay to secure a benefit or their willingness to accept
compensation for a loss). Such valuation techniques reflect economic circumstances
and value systems in the Organisation for Economic Cooperation and Development
(OECD). The estimates for non-OECD countries in Chapter 6 of the Working Group
III contribution to the SAR (IPCC, 1996) are based on extrapolation from studies
in the OECD. With these caveats in mind, Chapter 6 of the WG III contribution
to the SAR (IPCC, 1996) reports best estimates for the annual impact resulting
from a doubling of atmospheric concentrations of CO2 of about 2.1-8.6% of
GDP in South and Southeast Asia. These figures compare with an estimated world
impact of 1.4-1.9% of GDP. Many assumptions underlie these best guesses, however,
and large uncertainties remain.