Himalayan glaciers are among the fastest retreating glaciers globally due to the effects of global warming, and this will eventually result in water shortages for hundreds of millions of people who rely on glacier-dependent rivers in China, India and Nepal, warns WWF, the global conservation organization in a report released Monday.
The new WWF report – An Overview of Glaciers, Glacier Retreat and Subsequent Impacts in Nepal, India and China – reveals the rate of retreat of Himalayan glaciers accelerating as global warming increases. The report states that glaciers in the region are now receding at an average rate of 10–15 metres per year.
– The rapid melting of Himalayan glaciers will first increase the volume of water in rivers, causing widespread flooding, said Jennifer Morgan, Director of WWF’s Global Climate Change Programme adding:
– But in a few decades this situation will change and the water level in rivers will decline, meaning massive economic and environmental problems for people in western China, Nepal and northern India.
Himalayan glaciers feed into seven of Asias greatest rivers (the Ganges, Indus, Brahmaputra, Salween, Mekong, Yangtze and Huange He), ensuring a year-round water supply to hundreds of millions of people in the Indian subcontinent and China.
As glacier water flows dwindle, the energy potential of hydroelectric power will decrease causing problems for industry, while reduced irrigation means lower crop production.
Nepal has an annual average temperature rise of 0.06°C per year. The report shows that three of Nepals snow-fed rivers have shown declining trends in discharge.
In China, the report shows that Qinhai Plateaus wetlands have seen declining lake water levels, lake shrinkage, the absence of water flow in rivers and streams, and the degradation of swamp wetlands.
In India, the Gangotri glacier, which supports one of India’s largest river basins, is receding at an average rate of 23 metres per year.
The report is released on the eve of a two-day ministerial roundtable of the 20 largest energy using economies in the world, including China and India, followed by a G8 meeting of development and environment ministers focusing on climate change and on Africa.
Both meetings are hosted by the UK government in London from 15-18 March. WWF has sent a letter to participating ministers, stressing the need to recognize climate change as an issue that seriously threatens security and development prospects.
– Ministers should realize now that the world faces an economic and development catastrophe if the rate of global warming is not reduced, said Jennifer Morgan concluding:
– They need to work together on reducing CO2 emissions, increasing the use of renewable energy and implementing energy efficiency measures.
In a letter to the Ministers of Environment, Energy and Development attending the Ministerial roundtable and the G8 meeting, WWF
– calls on all governments to recognize that global average temperature must stay below 2°C (3.6°F) in comparison to pre-industrial levels,
– to agree upon a series of ambitious initiatives to vastly change the way their countries produce and use energy, and
– to launch a power sector governance initiative where all countries commit to practicing the principles of transparency, accountability and public participation in energy sector decision-making.
Her følger Executive Summary af rapporten, taget fra WWF Internationals website, www.wwf.org
Introduction
Climatic changes and its impacts on the fluctuation of glaciers are a natural phenomenon that has been occurring in the Earths five billion-year-old history. In the past few decades, global climate change has had a significant impact on the high mountain environment: snow, glaciers and permafrost are especially sensitive to changes in atmospheric conditions because of their proximity to melting conditions.
In fact, changes in ice occurrences and corresponding impacts on physical high-mountain systems could be among the most directly visible signals of global warming. This is also one of the primary reasons why glacier observations have been used for climate system monitoring for many years (Haeberli 1990; Wood 1990).
A historical overview
There have been at least 17 major glacial advances (glaciations – istider) in the last 1.6 million years alone (Goudie 1983). The most recent, the Last Glacial, reached its peak some 20.000 to 18.000 years ago and came to an end about 10.000 years ago (Goudie 1983). Glaciations are followed by “interglacial” periods (mellemistider), during which the glacier ice retreats as a result of global warming. The interglacial typically continues for about 10.000 years before the cooling or the next glaciation begins.
This cyclical activity, which recurs at intervals of approximately 100.000 years, is generally accepted to be caused by gradual changes in the Earths rotation, tilt and orbit around the sun, which affects the amount of solar radiation the earth receives (Milankovitch 1941 in Bradley 1985).
Glacial cycles are punctuated by relatively short periods of localized cooling and warming, during which glaciers advance and retreat. The most recent cooling episode of the present interglacial commonly referred to as the Little Ice Age (LIA), affected parts of North America (Curry 1969), Asia (Chu Ko-Chan 1973) and Europe from about 1300 AD through to the latter half of the 19th century.
During the LIA (1550-1850 AD) glaciers were much longer than today (Yamada et al. 1998). It may have been the result of volcanic eruptions and the presence of volcanic ash in the atmosphere that caused cooling by reducing the amount of solar radiation reaching the Earths surface (Lamb 1970). Changes to ocean currents have also been suggested, as has tectonic activity, concentration of carbon dioxide in the atmosphere, and sunspot activity (Goudie 1983).
The present scenario
The 20th century has been a watershed vis-à-vis glacial fluctuations on a global scale. This has been a period of dramatic glacier retreat in almost all alpine regions of the globe, with accelerated glacier and ice-fields melt in the last two decades.
The first phase of this glacier retreat was associated with emergence from the Little Ice Age that ended in the 19th century. It corresponded with a warming of 0.3ºC in the first half of the 20th century in the northern hemisphere (24o to 40°N). In the last 25 years, a second 0.3ºC warming pulse has caused northern hemisphere temperatures to rise to unprecedented levels compared to the last 1.000
years.
The 1990s were the warmest decade of the millennium and 1998 the hottest year of the millennium. In all, there was a temperature rise of close to 1ºC across the continents. Research shows that the glacier cover of mountain regions worldwide has decreased significantly in recent years as a result of warming trends.
A recent comparison of historical glacier data with images from the ASTER (Advance Spaceborne Thermal Emission and Reflection Radiometer) instrument on NASAs TERRA satellite by the United States Geological Survey revealed a significant shrinkage of mountain glaciers in the Andes, the Himalayas, the Alps and the Pyrenees over the past decade (Wessels et al. 2001).
These observations are consistent with published results from many other glacier studies around the world that also recorded rapid glacier retreat in recent years. A study by Dyurgerov and Meier (1997), who considered the mass balance changes of over 200 mountain glaciers globally, concluded that the reduction in global glacier area amounted to between 6.000 and 8.000 km2 over a 30 year period between 1961 and 1990.
According to Haeberli and Hoelzle (2001) of the World Glacier Monitoring Service (WGMS), the measurements taken over the last century “clearly reveal a general shrinkage of mountain glaciers on a global scale”. They observed that the trend was most pronounced during the first half of the 20th century and that glaciers had started to grow again after about 1950.
However, they claim that mountain glacier retreat has been accelerating again since the 1980s at a “rate beyond the range of pre-industrial variability”. Based upon a number of scientific investigations (e.g. Kuhn 1993a, Oerlemans 1994) and the IPCC (1996b) there are forecasts that up to a quarter of the global mountain glacier mass could disappear by 2050 and up to half could be lost by 2100.
Closer to the present focus of our areas of study, Himalayan glaciers have also been found to be in a state of general retreat since 1850 (Mayewski & Jeschke 1979). The Himalayan glaciers feed seven of Asias great rivers: Ganga, Indus, Brahmaputra, Salween, Mekong, Yangtze and Huang He, and ensure a year-round water supply to billions people.
The Khumbu Glacier, a popular climbing route to the summit of Mt Everest, has retreated over 5 km from where Sir Edmund Hillary and Tenzing Norgay set out to conquer the worlds highest mountain in 1953. Since the mid-1970s the average air temperature measured at 49 stations of the Himalayan region rose by 1°C with high elevation sites warming the most (Hasnain 2000).
This is twice as fast as the 0.6°C average warming for the mid-latitudinal northern hemisphere over the same time period (IPCC 2001b), and illustrates the high sensitivity of mountain regions to climate change (Oerlemanns et al. 2000). The Dokriani Barnak Glaicer in India retreated 20m in 1998, and the Gangotri Glacier some 30m.
Overview of the problem
The New Scientist magazine carried the article “Flooded Out – Retreating glaciers spell disaster for valley communities” in their 5 June 1999 issue. It quoted Professor Syed Hasnain, then Chairman of the International Commission for Snow and Ices (ICSI) Working Group on Himalayan Glaciology, who said most of the glaciers in the Himalayan region “will vanish within 40 years as a result of global warming”.
The article also predicted that freshwater flow in rivers across South Asia will “eventually diminish, resulting in widespread water shortages”. As apocalyptic as it may sound, it needs to be underlined that glaciers need to be studied for a variety of purposes including hazard assessment, effects on hydrology, sea level rise and to track climatic variations.
There are several problems associated with retreating glaciers that need to be understood in order to proceed to the next stage of quantifying research and mitigating disaster. In this context it would be imperative to understand the nature of problems that confront Nepal, India and China. While the following section deals with problems faced by all three countries, country-specific losses and details would be dealt with separately.
Risks and associated impacts of glacier retreat Freshwater regime
More than half of humanity relies on the freshwater that accumulates in mountains (Mountain Agenda 1998). Glaciers “mother” several rivers and streams with melt runoff. A significant portion of the low flow contribution of Himalayan rivers during the dry season is from snow and glaciers melt in the Himalayan region.
The runoff supplies communities with water for drinking, irrigation and industry, and is also vital for maintaining river and riparian habitat. It is posited that the accelerated melting of glaciers will cause an increase in river levels over the next few decades, initially leading to higher incidence of flooding and land-slides (IPCC, 2001a). But, in the longer-term, as the volume of ice available for melting diminishes, a reduction in glacial runoff and river flows can be expected (IPCC 1996b, Wanchang et al. 2000).
In the Ganga, the loss of glacier meltwater would reduce July-September flows by two thirds, causing water shortages for 500 million people and 37 percent of Indias irrigated land (Jain 2001; Singh et al. 1994). Glacial lake outburst floods (GLOFs) Glacial lake outburst floods (GLOFs) are catastrophic discharges of water resulting primarily from melting glaciers.
An accelerated retreat of the glaciers in recent times has led to an enlargement of several glacial lakes. As the glaciers retreat they leave a large void behind. The ponds occupy the depression earlier occupied by glacier ice. These dams are structurally weak and unstable and undergo constant changes due to slope failures, slumping, etc. and run the risk of causing GLOFs.
Principally, a moraine dam may break by the action of some external trigger or self-destruction. A huge displacement wave generated by rockslide or a snow/ice avalanche from the glacier terminus into the lake may cause the water to top the moraines and create a large breach that eventually causes dam failure (Ives 1986).
Earthquakes may also be one of the factors triggering dam break depending upon magnitude, location and characteristics. Self-destruction is a result of the failure of the dam slope and seepage from the natural drainage network of the dam.
Characterized by sudden releases of huge amounts of lake water, which in turn would rush down along the stream channel downstream in the form of dangerous flood waves, GLOF waves comprise water mixed with morainic materials and cause devastation for downstream riparian communities, hydropower stations and other infrastructure.
In South Asia, particularly in the Himalayan region, it has been observed that the frequency of the occurrence of GLOF events has increased in the second half of the 20th century. GLOFs have cost lives, property and infrastructure in India, Nepal and China. Glacial Lake Out-burst Floods (GLOF) are the main natural hazards in the mountain areas of this region.
A 1964 GLOF in China destroyed many kilometers of highway and washed 12 timber trucks 71 km from the scene. An outburst of Zhangzangbo Lake in 1981 killed four people and damaged the China-Nepal Friendship Bridge in the northern border, seven other bridges, a hydropower plant, Arniko highway and 51 houses. The damage was estimated to be USD 3 million.
The 1985 GLOF at Dig Tsho was triggered by a large avalanche. A hydroelectricity project, 14 bridges, 30 houses and farmlands worth USD 4 million were destroyed. In 1998, the outburst of Tam Pokhari in Nepal killed two people, destroyed more than six bridges and washed away arable land. Losses worth over 150 million rupees have been estimated.
A high water level was observed even after 19 hours in the Koshi barrage near the Indo-Nepal border. The river reverted to its original flow only after three days (Dwivedi 2000). There are about 159 glacier lakes in Koshi basin (Sharma 1998). Nearly 229 glacier lakes were identified in Tibets Arun basin, out of which 24 are potentially dangerous (Meon & Schwarz 1993).
Since 1935 more than 16 GLOFs have been reported which either occurred or extended into Nepal. National economic costs For a landlocked country like Nepal, which relies on hydropower generation as a vital source of national income, the prospect of an eventual decrease in the discharge of rivers spells doom.
For an energy-constrained economy like India, the prospect of diminishing river flows in the future and the possibility that energy potential from hydropower may not be achieved has serious economic implications.
The implications for industry extend beyond the “energy” argument: chemical, steel, paper and mining industries in the region that rely directly on river/stream water supply would be seriously affected. Reduced irrigation for agriculture would have ramifications not only on crop production but eventually on basic human indices like available food supplies for people and malnutrition.
While the impacts of deglaciation are briefly outlined in the aforementioned categories there are, as mentioned earlier, details specific to each of the countries that will be dealt within the country-specific case study. It would be useful to refer to each country analyses with the thematic support literature covered in the previous sections.
The country case-studies are useful in understanding physical and climatological characteristics of the region and serve as useful bases of reference for further research.
The full report can be downloaded at:
www.panda.org/downloads/climate_change/himalayaglaciersreport2005.pdf
