Severe storms, floods and droughts since the eighties have served as reminders that climate change is a global problem. The most dramatic change has been in the temperature, with measurement records suggesting that warming by 0.3-0.6 °C has already taken place since the 1860s. The last two decades of the 20th century were the warmest in this period.

Over the next hundred years, the earth's surface temperature is projected to increase by 1.4 to 5.8 °C which will be greater than that experienced over the last 10 000 years.

Climate changes have occurred in the past, but always gradually, over thousands of years, giving ecosystems time to adapt. The rapid change that is currently taking place will leave ecosystems vulnerable. The large quantities of water locked in the polar ice caps and glaciers will be released as a consequence of warming. This, together with an increase in the thermal expansion of the oceans, will make the global mean sea level rise by 9 cm to 88 cm.

The river Ganga originates in the Himalayas, and is fed by several glaciers. The Gangotri is the longest of these, at 26 km, but there are hundreds of smaller ones, too. One of these, is the Dokriani Bamak which is 5 km long and has a permanent research station at its base. Scientists studying this glacier have found that it has been retreating at a rate of 20 m a year compared to about 16 m per year in the past. If the present trend continues, then over the next 25 years, the Ganga could initially swell in volume because of increased melting but then dry out as the water supply in the mountains runs low. This will endanger the lives of about 400 million people who live in the river's plains and depend upon it for their supply of water.

The effects of global warming are difficult to quantify because of the complicated relationships between air temperature, precipitation quantity and pattern, vegetative cover and soil moisture. However, it is likely that the frequency, intensity and duration of storms and other extreme weather events could increase.

The costs of catastrophic weather events have exhibited a rapid upward trend in recent decades. Yearly economic losses from large events increased 10.3-fold from US$4 billion yr-1 in the 1950s to US$40 billion yr-1 in the 1990s (all in 1999 US$). The insured portion of these losses rose from a negligible level to US$9.2 billion annually during the same period, and the ratio of premiums to catastrophe losses fell by two-thirds. Notably, costs are larger by a factor of 2 when losses from ordinary, noncatastrophic weather-related events are included. The numbers generally include "captive" self-insurers but not the less-formal types of self-insurance. Source IPCC Third Assessment Report: Climate Change 2001 (Impacts, Adaptation & Vulnerability, Chapter 8, Insurance and Other Financial Services)

Climate change is likely to have an impact in the following ways:
By the 2080's, substantial dieback of tropical forests and grasslands is predicted to occur, particularly in parts of South America and Africa.
The availability of water in the rivers of Australia, India, southern Africa, South America, Europe and the Middle East is expected to decrease.

Impact of climate change on water resources by 2050 with 1% per annum increase in CO2 concentration. Source IPCC Third Assessment Report: Climate Change 2001 (Synthesis Report)

Cereal yields in Africa, the Middle East and India are likely to decline.

Changes in crop yield by the 2080's with unmitigated emissions Source DETR 1999

A rise in sea level could inundate and erode coastal areas, increase flooding and salt-water intrusion; this will affect coastal agriculture, fisheries and aquaculture, freshwater resources, human settlements and tourism.
The incidence of water-borne diseases, heat stress and vector-borne diseases such as malaria is expected to increase.

All developing countries facing the problems of population and economic growth will be put under even greater stress as a result of these impacts.

In India, climate change could represent additional pressure on ecological and socio-economic systems that are already under stress due to rapid urbanization, industrialization, and economic development. With its huge and growing population, a 7500-km long densely-populated and low-lying coastline, and an economy that is closely tied to its natural resource base, India is considerably vulnerable to the impacts of climate change.

Most countries in temperate and tropical Asia have already felt the impact of extreme climate events such as droughts and floods. The intensity of extreme rainfall events is projected to be higher in a warmer atmosphere, suggesting a decrease in return period for extreme precipitation events and the possibility of more frequent flash floods in parts of India, Nepal, and Bangladesh (Lal M, Meehl G A, and Arblaster J M. 2000).

Increases in temperature and seasonal variability in precipitation are expected to result in more rapid recession of Himalayan glaciers. In fact, the Gangotri glacier is already retreating at a rate of 30 metres a year.

An increase in rainfall is simulated over the eastern region of India but the northwestern deserts may see a small decrease in the absolute amount of rainfall.

Warmer and wetter conditions would increase the potential for a higher incidence of heat-related and infectious diseases. The incidence and extent of vector-borne diseases, which are significant causes of mortality and morbidity in tropical Asia, are likely to spread into new regions on the margins of present endemic areas as a result of climate change.

The impacts on specific sectors in India:

Agriculture
Forests
Coastal areas

References

DETR. 1999
Climate change and its impacts: stabilization of carbon dioxide in the atmosphere
Bracknell, UK: Hadley Centre for Climate Prediction and Research. 28 pp.

Lal M, Meehl G A, and Arblaster J M. 2000
Simulation of Indian summer monsoon rainfall and its intraseasonal variability
Regional Environmental Change 1(3/4): 163-179

Agriculture Forests Coastal areas

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