Climatologically, India can be divided in seven distinct regions namely, the northern Mountains, the northern plains, the Deccan plateau, the west coast, south-east coastlands and north east region. These regions represent extreme to moderate climates. Broadly, the regions can be categorised as – Himalayan belt, Coastal region, Gangetic plain and Deserts. All of these are adversely impacted by climate change through increased temperature, altered precipitation patterns, and episodes of drought. Also, because of its long coastline India is identified as one of the countries that would be vulnerable to sea level rise.

Climate Change in Himalayan Region

The Himalayan region, one of the most dynamic and complex mountain ranges, has a profound effect on the climate of the Indian subcontinent. It prevents frigid, dry Arctic winds from blowing south into the subcontinent, which keeps South Asia much warmer than corresponding temperate regions in the other continents. It also forms a barrier for the monsoon winds, keeping them from travelling northwards, and causing heavy rainfall in the Terai region.

But now Himalayas are vulnerable to global climate change and increasing human activities. In addition to the already existing threats and pressures on mountain ecosystem, climate change can be an additional burden to bear by the mountain ecosystems, species and peoples. Mountain people have lived with and survived great hazards for thousands of years, but current rates of climate change are among the most rapid known and they are superimposed on severe and, equally uncertain socioeconomic pressures. Mountain regions are seeing the greatest impacts on livelihoods and ecosystems with reduced ice and snow cover affecting biodiversity and water resources.

A range of issues and policy areas are identified, from the regional to local community levels, through which these problems might be addressed. They involve land use, water management, disaster management, energy consumption, and human health. It is argued that community-led adaptive strategies and capacities, as well as substantial efforts to reverse the human drivers of climate change, are needed [1].

Uncertainties about the rate and magnitude of climate change and potential impacts prevail, but there is no question that it is gradually and powerfully changing the ecological and socioeconomic landscape in the Himalayan region.

Melting Glaciers in Himalayas

The Himalayan glaciers are the second largest body of ice in the world, covering 17% (3 million hectares) of the mountain area and are the source of water for the numerous rivers that flow across the Indo-Gangetic plains. Unfortunately, the Himalayan glaciers are retreating faster than any other glaciers [2] . The image shows the approximate recession of the Gangotri glacier- one of the largest glaciers in the Himalayans. From 1780 to 2001 this glacier retreated almost 2 km.

Compared to other glaciers around the world, there is a lack of information on the impact of global warming on the Himalayan glaciers. Described as “a blind spot, a big scientific question mark” scientists are working to correct this gap [3].

Millions of the peoples living in Himalayan region are relying on the glacial melt waters from the Himalayan glaciers. A decline in glacier mass balance can mean less water available for rivers. It is a worry that the receding glacier trend could lead to the Ganga, Indus, Brahmaputra and other rivers in northern India becoming seasonal rivers (IPCC 2007). If these major rivers are dry during the summer months. It will affect the water supply for irrigation.

Impacts on water and agriculture

The presence of highly complex river basin systems indicates the importance of glaciated mountains, which account for most of the glacial melt water. Both glacial melt water and monsoonal precipitation provide a significant component of water resources for different parts of the country. While snow and glacier melt are the major factors in the western and central Himalayan region, rainfall patterns in the eastern part of India are responsible for the changing water regime.

Impact of deglaciation on the water resources of the Himalayan region and change in local water discharges can respond to future climate scenarios. This may results in increased water availability in some river basins and decreased water supplies in other regions in the coming decades. The glacial fed rivers of Uttarakhand are an important resource for the Ganga basin with many rivers contributing to the irrigation potential of some of India’s most densely populated states like Uttar Pradesh, Bihar, Delhi, Haryana etc.

Loss of glaciers, runoff and river flow

A very robust finding of hydrological impact studies is that warming leads to change in the seasonality of river flows where much winter precipitation currently falls as snow. Many rivers draining glaciated regions, particularly in the Hindu Kush-Himalaya are sustained by glacier melt during the summer season [4] . Higher temperatures generate increased glacier melt. As these glaciers retreat due to global warming, river flows are increased in the short term, but the contribution of glacier melt will gradually decrease over the next few decades.

In the higher reaches of Himalayas, snowfall builds up from year to year to form glaciers that provide long-term reservoirs of water stored as ice. The Himalayan range has a total area of 35,110 sq. km of glacier and ice cover, with a total ice reserve of 3,735 cu. Km[5] . Climate controls river flow and glacier mass balance in the Himalayan region, and these vary considerably from west to east.

The variations in the hydrological cycles of rivers in India are determined mainly by the seasonality of the precipitation and the temperature, which governs the ratio between snow and rainfall. It is found that annual snowmelt run off, glacier melt run-off and total stream flow increase linearly with change in temperature (1-3 oC), but the most prominent effect of increase in temperature has been noticed on glacier melt run off .

Flooding and flood frequency

A warmer climate, with its increased climate variability, will increase the risk of floods. As there are a number of climatic and non-climatic drivers influencing flood impacts, the realization of risks depends on several factors. Floods include river floods, flash floods, urban floods and sewer floods, and can be caused by intense and/or long-lasting precipitation, snowmelt, dam break, or reduced conveyance due to ice jams or landslides. Floods depend on precipitation intensity, volume, timing, antecedent conditions of rivers and their drainage basins (e.g., presence of snow and ice, soil character, wetness, urbanization, and existence of dikes, dams, or reservoirs). Human encroachment into flood plains and lack of flood response plans increase the damage potential.

With more than one-sixth of the Earth’s population relying on melt water from glaciers and seasonal snow packs for their water supply, the consequences of projected changes for future water availability, predicted with high confidence and already diagnosed in some regions, will be adverse and severe1. Drought problems are projected for regions, which depend heavily on glacial melt water for their main dry-season water supply5. Rapid melting of glaciers can lead to flooding of rivers and to the formation of glacial melt-water lakes, which may pose a serious threat of outburst floods. The entire Hindu Kush-Himalaya ice mass has decreased in the last two decades. Hence, water supply in areas fed by glacial melt water from the Himalayas, on which millions of people in India depend, will be negatively affected [6].

Additional Reading:

Climate Change In Relation To The Himalayas – S. P. Singh

Indian Coastal Zone

The coastal zone is an important and critical region for India. More than 100 million peoples of the Indian population live along the 7510 km country’s coasts, with an average population density of 455 persons per km2 (Fig. 1), which is about 1.5 times the national average of 324 (Census, 2001). Climate change effects on sea level can impact coastal areas in two ways – through increase in mean sea level, and through increased frequency and intensity of coastal surges and storms. Climate change is of concern to India in view of the damages that occur along the east coast of India from the cyclones that form in the Bay of Bengal. Any increase in the frequency or intensity of tropical disturbances due to climate change in the future could cause increased damages to life and property in the coastal regions.

Future climate change in the coastal zones is likely to be manifested through the worsening of climate related problems like erosion, flooding, subsidence and deterioration of coastal ecosystems. The key climate related risks in the coastal zone includes tropical cyclone, sea level rise, and changes in temperature and precipitation.

It is expected that a rise in global temperatures will bring a rise in sea levels, with adverse impact. The observed trends in the mean sea level along the Indian coast indicate a rising of about one centimeter per decade, which is close to that noticed in other parts of the globe. The projected future sea level rise could inundate low-lying areas, coastal marshes and wetlands, erode beaches and increase flooding and salinity of rivers, bays and aquifers.

Sea-level Rise

Climate warming will lead to thermal expansion of water and melting of glacier and polar land ice, with a subsequent rise in sea level. The effects of sea-level rise will vary with location, speed of the rise, and the geological and biological responses of the affected ecosystems. Using the available models, global sea-level rise of 10-25 cm per 100 years has been predicted due to the emission of GHGs. A rise in sea level has significant implications on the coastal population and agricultural performance of India. According to India’s NATCOM[7] report variety of impacts are expected which include:

• Land loss and population displacement.
• Increased flooding of low-lying coastal areas.
• Agricultural impacts (like, loss of yield and employment) resulting from inundation, salinization, and land loss.
• Impacts on coastal aquaculture.
• Impacts on coastal tourism, particularly the erosion of sandy beaches.

Sea level rise will affect many regions, with the Andaman and Nicobar islands, the Lakshadweep island in the south western part, the low lying deltaic region in West Bengal, and the Couch region in Gujarat are likely to be the most vulnerable area [8]. Additionally, increased occurrence of extreme events due to climate change will also affect the poor the most as their adoptive capacities are less. The coastal zone in India is frequently affected by cyclones and sea level rise is going to be an area of concern for the country.

Additional Reading:

DEFRA Climate Key Sheet 4: Climate Change Impacts on Sea Level in India

Desert

Deserts are unique, naturally occurring environments characterized by low and irregular rainfall (less than 100mm a year on average) and extreme temperatures. The dry conditions found in deserts have resulted in a limited number of human inhabitants. Despite this, deserts sustain a diverse range of plants and animals as many species including reptiles and mammals have developed ingenious ways to cope with the extremes[9] .

Among the findings of UNEP’s Global Desert Outlook, climate change impacts are listed as the greatest threat. Climate change over the past 25 years has caused temperatures to rise faster in the deserts, up to 2 OC, than the global average of 0.45 OC. The study found also that most deserts will see temperature rise by 5-7 OC by the end of the century and rainfall drop 10-20%. According to UNEP these vast open spaces, home to rare and useful plants and animals, are at risk from climate change and human exploitation.

Climate change impact on Indian Desert

The arid western part of Indian subcontinent, including the western part of Rajasthan state, containing the Thar Desert is likely to experience large scale changes due to changing climatic conditions. The region is already witnessing subtle change in rainfall[10]. The spatial patterns of changes in rainfall and temperature in arid western part of India suggest the likely evolution of three major sub zones in the regions climate.

• The hotter and very dry north west Rajasthan and adjoining Punjab
• The warmer and moderately wetter arid Gujrat and adjoining Rajasthan
• The hotter and slightly wetter eastern fringe of arid Rajasthan and adjoining Haryana

These patterns are not encouraging for agriculture related activities in most part of the Indian desert and its fringes. Higher temperature in association with reduced rainfall will desiccate the soil further and reduce chances of crop survival. Considering that the north western part of the desert is likely to far drier than northwestern part of the desert is likely to be far drier than at present. It is high time to identify appropriate adaptation options.

FOOTNOTES

• 1. Jianchu Xu, Shrestha A., Vaidya, A., Eriksson M., and Hewitt K. (2007) The melting Himalayas: Regional challenges and local impacts of climate change on mountain ecosystem and livelihoods, ICIMOD Technical Paper, pp15.↑
• 2. IPCC (2007) Climate Change 2007: Impacts, Adaptation and Vulnerability.↑
• 3. http://arabianseaclimate.blogspot.com/2008/07/melting-glaciers-himalayas.html ↑
• 4. Barnett, T.P.; Adam, J.C.; Lettenmaier, D.P. (2005) ‘Potential Impacts of a Warming Climate on Water Availability in a Snow-dominated Region’. In Nature, 438(17): 303-309↑
• 5. Jianchu Xu, Shrestha A., Vaidya, A., Eriksson M., and Hewitt K. (2007) The melting Himalayas: Regional challenges and local impacts of climate change on mountain ecosystem and livelihoods, ICIMOD Technical Paper, pp15.↑
• 6. Singh, P. and N. Kumar, 1997: Impact assessment of climate change on the hydrological response of a snow and glacier melt runoff dominated Himalayan river. J. Hydrol., 193, 316-350.↑
• 7. India’s National Communication to UNFCC, 2004, MoEF, Govt. of India, New Delhi.↑
• 8. Asthana, V., 1993. Impact of sea level rise on the islands and coasts of India. Report submitted to MoEF, Govt. of India, New Delhi↑
• 9. http://www.oxfam.org.uk/coolplanet/onth eline/explore/nature/deserts/climate.htm↑
• 10. Kar A. 2008, Climate change impact on the Thar Desert, Geography and You, Vol. 8, pp36-40↑