Impact of climate change in Asia

Print edition : March 31, 2001

The Himalayas have nearly 1,500 glaciers and it is estimated that these cover an area of about 33,000 sq km. Snow, ice, and glaciers in the region are approximately equivalent to about 1,400 cu.km of ice. These glaciers provide the snow and the glacial-m elt waters that keep the major rivers perennial throughout the year. The total amount of water flowing from the Himalayas to the plains of the Indian subcontinent is estimated at about 8.6 M cu.m per year...Rise in temperature and increase in seasonal va riability in precipitation are expected to result in a more rapid recession of the Himalayan glaciers.

Almost 67 per cent of the glaciers in the Himalayan and Tienshan mountain ranges have retreated in the past decade. The mean equilibrium line - the altitude at which snow accumulation is equal to snow ablation for a glacier - is estimated to be about 50- 80 m higher relative to the altitude during the first half of the 19th century. Available records suggest that Gangotri glacier is retreating about 30 m per year. A warming is likely to increase the melting far more rapidly than the accumulation... Glaci al melt is expected to increase under changed climatic conditions, which would lead to increased summer flows in some river systems for a few decades, followed by a reduction in the flow as the glaciers disappear.

-- From the Chapter on Asia in the Special Report of the Inter-governmental Panel on Climate Change (IPCC) "The Regional Impacts of Climate Change: An Assessment of Vulnerability", February 2001.

ONE of the companion reports to the Third Assessment Report (TAR) of the IPCC released in February is a special report titled "The Regional Impacts of Climate Change: An Assessment of Vulnerability". Its chapter on Tropical Asia looks at the likely impa cts of warming owing to increased greenhouse gas (GHG) emissions and atmospheric aerosols. It must be pointed out that the global climate models (GCMs) used for the purpose of the report have included only the effects of sulphate aerosols and not those o f other aerosols, such as soot, dust and other fine particulate matter.

As a result of the continued emissions of GHGs, the spatial average over the Asian region of the annual mean warming would be about 3oC in the 2050s and about 5oC in the 2080s, says the report based on GCM simulations. Under the com bined influence of GHGs and sulphate aerosols, however, the warming would be restricted to about 2.5oC and about 4oC respectively. In general, according to the report, the warming is expected to be higher during the northern hemisph ere (NH) winter than during the summer. The GCM simulations project relatively more pronounced increases in the minimum temperature than in the maximum temperature during the winter and hence a decrease in the diurnal temperature range (DTR). However, du ring the summer the DTR is expected to increase, suggesting a more pronounced increase in the peak temperature rather than the minimum temperature.

Warming owing to GHGs alone is expected to result in an annual mean increase in rainfall of about 7 per cent in the 2050s and about 11 per cent in the 2080s over the land regions of Asia. Under the combined influence of sulphate aerosols, the projected i ncrease in precipitation drops to 3 per cent and 7 per cent respectively. Again, as above, the projected increase is the maximum during the NH winter. Specific to the South Asian region is the fact that much of tropical Asia is intrinsically linked to th e annual monsoon cycle. Since the behaviour of this weather system to changes in climate is not well understood, the report says that projections by the GCMs have a high level of uncertainty with regard to both summer and winter rainfall over the South A sian region.

The report has also looked at the vulnerabilities in the region and possible strategies for adaption to climate change. Since surface water and ground water resources play a vital role in Asian economies, the water and agricultural sectors are likely to be the most sensitive to climate change, says the report. Fresh water availability is expected to be highly vulnerable to the anticipted climate change. While the frequency and severity of floods would eventually increase in many countries of Asia, the a rid and semi-arid regions could experience severe water stress. The impact on the ecology of mountain and highland systems could be serious, the report says. Many species of mammals and birds and a large population of many other species could be extermin ated as a result of the synergic effects of climate change and habitat fragmentation. Glacial melt is also expected to increase under the changed climatic conditions. This would lead to increased summer flows in the rivers for a few decades followed by a reduction in the flow as the glaciers disappear.

Agricultural productivity is likely to suffer severely due to high temperature, severe drought and flood conditions and soil degradation. As a result, the food security of many countries in the region would be under threat. Aquaculture productivity is al so likely to undergo dramatic changes as a result of temperature changes in water. The rise in the sea level would cause submergence of large tracts of the vast Asian coastline, leading to a recession of flat sandy beaches. The ecology of mangroves and c oral reefs around Asia too is likely to suffer severely.

In a warmer climate, the El Nino-Southern Oscillation (ENSO) events become stronger and more frequent. Therefore, their impact on the Asian monsoon could lead to high inter-annual variation in rainfall characteristics. The countries in temperate and trop ical Asia are likely to have increased exposure to extreme events. The frequency of forest fires is expected to increase, particularly in the Boreal Asia region.

Tropical cyclones could become more intense. When combined with the sea level rise, this would result in an enhanced risk of loss of life and property in the coastal low-lying areas in cyclone-prone regions. Warmer and wetter conditions would increase th e potential for a higher incidence of heat-related and infectious vector-borne diseases such as malaria and dengue. Climate change would also exacerbate the threat to biodiversity due to changes in land use and land cover and population pressure.

The developing countries of Asia, where impacts of climate change are likely to be felt most severely because of resource and infrastructure constraints, "need to develop and implement incremental adaption strategies and policies to exploit no-regret mea sures and win-win options", says the report. Stressing the importance of considering climate change in planning, designing and implementing development activities, the report has advocated two general strategies.

The first is a macro strategy and involves rapid sustainable and equitable development that will increase income levels, education and technical skills, improve public food distribution, disaster preparedness and management and health care systems and re duce vulnerability. The second strategy is a micro strategy and involves the management of sectors most sensitive to the climate change. This means developing new institutions or modifying existing ones to promote adaption to climate change. It would als o involve modifying climate-sensitive infrastructures already planned or implemented or other long-term decisions that are sensitive to climate.

The report has specifically called for conservation of water resources to be the priority issue in all future adaption strategies for the countries of the region. For countries with a large population, such as India, China and Bangladesh, disaster prepar edness and management, soil conservation and human health sectors would be crucial, it says.

The seriousness of the situation has, however, not dawned on Indian policy-makers, feels Murari Lal of the Indian Institute of Technology (IIT), Delhi, one of the lead authors of the chapter on Asia. There is not even an effort to understand the implicat ions of a climate change, let alone evolve systems to mitigate the impact, he feels. "We have not even put in place mechanisms to carry out an inventory of GHG emissions, as mandated by the United Nations Convention. Although there is money coming from t he global environmental fund, there is no system to plan and make use of the fund properly," he says.

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