This chapter discusses the current status of our understanding of likely future changes in climate variables, such as surface temperature, precipitation, soil moisture, extreme events, their potential impacts on natural environment and human society, and possible adaptative options in the Asian region. These factors are delineated on a subregional, national, and sectoral basis. This section attempts to formulate a synthesis of climate change and its implications and consequences for Asia and identify commonality throughout the region, as well as subregional and national differences in terms of climate change and its consequences.

This synthesis also aims to identify the critical climatic threshold, feedbacks, interactions and nonlinearities involved in interactive systems of climate, natural environment, and human society. These analyses will provide a basis for further indepth understanding of the implications of climate change, setting policy-oriented goals to arrest human interventions to the climate system, and planning adaptive responses.

Asia is characterized by an extreme diversity of natural environment, in longitudinal, latitudinal, and vertical directions. Each subregion and country is supported by natural resources such as water, forests, grasslands/rangelands, and fisheries, which have been utilized by diverse Asian societies in a sustainable manner over the centuries. Promotion of public awareness and participation in region-specific adaptation and mitigation strategies is essential, however, particularly in the developing countries of Asia, to effectively and collectively overcome problems associated with climate change. In general, climate change will impose significant stresses on available natural resources throughout Asia. At the same time, combinations of specific geographical settings and changes in climate will bring about different impacts on different subregions.

Asia has long been affected by natural hazards such as intense rainfall, flooding, droughts, extreme temperatures, snow avalanches, and other impacts of tropical cyclones, monsoons, and ENSO. The security and sustainability of the region is highly dependent on future trends of such extreme events and preparedness for them. However, there remains great uncertainty in projections of likely changes in tropical cyclones, monsoons, and El Niño. It should be noted that the key vulnerabilities related to such natural hazards are still largely qualitative, and there are possibilities of unforeseen surprises in the future.

Many systems are sensitive to natural climate variability in Asia as well as climate change and hence may not be resilient to climate change. These systems include mangroves, lakes, glaciers, deltas, rivers, and ecosystems within the permafrost region. Threshold levels of response are likely to be exceeded by projected climate change. Changes in these systems will occur at different climate thresholds in various regions of Asia. For example, a 0.5°C rise in mean temperature and 10-cm rise in sea level could lead to inundation of 15% (approximately 750 km²) of the Bangladesh Sundarbans, the largest mangrove ecosystem in Asia. A 45-cm rise in sea level, corresponding to a 2°C rise in mean temperature, is required to introduce changes in the low saline zone of the Sundarbans (Smith et al., 1998). Table 11-10 lists selected examples of regions that are sensitive to climate change, based on region- and country-specific studies.

Table 11-10: Sensitivity of selected Asian regions to climate change (based on ICRF, 1998; Mirza, 1998; Smith et al., 1998; Mizina et al., 1999).
Change in Climatic Elements and Sea-Level Rise	Vulnerable Region	Primary Change	Impacts
			Primary	Secondary
0.5-2°C (10- to 45-cm sea-level rise)	Bangladesh Sundarbans	- Inundation of about 15% (~750 km2) - Increase in salinity	- Loss of plant species - Loss of wildlife	- Economic loss - Exacerbated insecurity and loss of employment
4°C (+10% rainfall)	Siberian permafrosts	- Reduction in continuous permafrost - Shift in southern limit of Siberian permafrost by ~100-200 km northward	- Change in rock strength - Change in bearing capacity - Change in compressibility of frozen rocks - Thermal erosion	- Effects on construction industries - Effects on mining industry - Effects on agricultural development
>3°C (>+20% rainfall)	Water resources in Kazakhstan	- Change in runoff	- Increase in winter floods - Decrease in summer flows	- Risk to life and property - Summer water stress
~2°C (-5 to 10% rainfall; 45-cm sea-level rise)	Bangladesh lowlands	- About 23-29% increase in extent of inundation	- Change in flood depth category - Change in monsoon rice cropping pattern	- Risk to life and property - Increased health problems - Reduction in rice yield

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