Like in many other countries, now-a-days, climate change has become a common topic in Nepalese society, too. Many awareness programs and researches are running from grass root level to national and international levels in this regard, for example, functioning of community level environmental groups, school level awareness groups and national level environmental groups. The establishment of hydrometeorological stations in the Himalayan region and various researches (some are joint research with international agencies) carried out by the Department of Hydrology and Meteorology (DHM), HMG/Nepal, researches carried out by the Water and Energy Commission Secretariat, glacier and glacier lake inventory of Nepal and other related works by International Center for Integrated Mountain Development, scientific research of Khumbu glacier by United Nations Environmental Program, and researches carried out by other agencies are some of the works carried out in this regard in Nepal. The most recent one in this regard is the initiation of joint research program between World Wildlife Fund-Nepal and DHM to study glacier retreat and climate change in the Khumbu region. These are very positive initiations indeed because Nepal may face various disturbances in its water resources and water induced disasters with climate change. We can imagine this with substantial reservoirs of water stored in the form of snow and glacier ice and in glacial lakes in the Himalayan region.

In the Earth Science a glacier, which is a huge body of ice moving down on a slope or valley, is taken as a good indicator of climate change. Glaciers develop in regions where the amount of the total depositing mass of snow exceeds the total mass of snow melting in polar and high mountain regions. There are two types of glaciers in the Himalayas; debris-free and debris-covered glaciers. Debris is aggregate of rock, gravel, sand, soil etc. In general, large valley glaciers are covered with debris on its lower part and its melting process is different from the debris-free ones; very thin debris cover tends to accelerate ablation, whereas debris thicker than few centimeters tends to insulate the underlying ice and inhibits ablation. Ngozumpa and Khumbu glaciers are two debris-covered large valley glaciers with surface area 88.89 and 41.33 sq. km, respectively in the Khumbu region. If the climate were to remain constant for a longer period, the size and shape of the glaciers would never change. A glacier sometimes changes size and shape due to climatic change. A glacier would advance further down and expand with the climate changing to a cool summer and heavy snowfall in winter and in the monsoon season. A glacier would retreat or become small with the climate changing to a warmer summer and less snowfall. Nepalese glaciers receive considerable amount of snowfall in the summer monsoon season. This is a typical characteristic of Nepalese glaciers compared to glaciers in the European Alps and other regions where accumulation occurs mainly in winter. Due to this typical characteristic, Nepalese glaciers are more vulnerable to climatic change than glaciers of other regions. Because effect of increase of air temperature is more on such glaciers since it reduces amount of snowfall (less snow but more rain) considerably during precipitation in summer monsoon.

Mass balance of a glacier is the balance of mass (snow and ice) in a given year. The glacier mass balance in any time is the algebraic sum of the accumulation (all processes of mass gain) and ablation (all processes of mass loss). Mass balance studies form an important link in the chain of events connecting advances and retreats of glacier with changes in climate. Only 2-3 glaciers in the Nepalese Himalayas have few years’ mass balance data and hence the glacier length variation is taken as a measure to interpret climatic change. However, the Equilibrium Line Altitude (ELA) of a glacier is more useful parameter. Equilibrium line is the line on a glacier above which the glacier has a net gain of mass over the year and below it there is a net loss. The altitude of this line is called the ELA. The ELA of a glacier represents the climatic condition of the glacier regime and fluctuates by changes in both temperature and precipitation. Since ELA is determined by the mass balance of the glacier which is mainly controlled by climatic parameter, its changes is controlled by climatic parameters. The understanding of causes of change of the ELA in two different time helps to know the climatic change during that period. Regarding the estimation of ELA, mass balance data is not the only way to locate it. It can also be estimated on the basis of geomorphological characteristics of glaciers.

My recent study about the changes ELA between the Little Ice Age (LIA) to 1959 and 1959 to 1992 in eastern Nepalese Himalayas shows that rate of upward shift of ELA is more between 1959 and 1992 than between the LIA and 1959. The LIA is a period of expansion of mountain glaciers, marked by climatic deterioration that began about 5500 years ago and extended as late as AD 1550-1850 in some regions. The data used in this study is glacier inventory of eastern Nepal (Kanchanjunga, Khumbu, Rolwaling and Langtang regions) prepared by a Japanese scientist. Based on the studies of annual moraine ridge of Yala Glacier in the Langtang valley and the tree-ring chronology in Nepal , the end of the LIA in east Nepal can be taken as AD 1815. The average rate of upward shift of ELA of debris-free glaciers from 1815 to 1959 is 0.38 m per year, compared to an average rate of 0.76 m per year between 1959 and 1992. In the case of debris-covered glaciers these rates are 0.22 and 0.42 m per year, respectively. Thus the retreat of Nepalese glaciers appears to be taking place at an accelerated rate in recent decades. The above results are based on 113 debris-free and 51 debris-covered glaciers in eastern Nepal . The ELA-climate model shows that the maximum shift of ELA, 84 m in Rolwaling region during the period between the LIA and 1992 may have been caused by either increase of temperature by 0.91 oC or decrease of precipitation by 164 mm per year. The Kathmandu Indian Embassy temperature record from 1897 to 1977 shows the temperature was increased by 0.27 oC. The major warming occurred after that which is about 1.0 oC between 1978 and 1992 in Kathmandu . Thus the total warming in Kathmandu from 1897 to 1992 is about 1.27 oC and this warming alone can shift the ELA by about 84 m in the Rolwaling region during the period between the LIA and 1992. However, one may question the applicability of the warming in Kathmandu city area to the northern Himalayan region. As an answer to this question, a recent study in this regard found more warming in the high-elevation regions compared to southern regions of Nepal . The distribution of precipitation at the Kathmandu Indian Embassy from 1852 to 1950 and at the Kathmandu Airport from 1968 to 1996 does not show significant trend. Therefore, the main probable cause for the upward shift of the ELA is increase in temperature and its effect is less on debris-covered glaciers than on debris-free glaciers.

Besides the upward shift of the ELA due to climatic change, increased discharge from two glacierized river basins are also found in Nepal. My another recent study found that the discharge from Langtang and Lirung Khola Basins in the Langtang valley is increasing, as the temperature increases although the precipitation amount did not change much from 1985 to 1999. It implies that the mass of snow and ice in both basins are depleting and hence discharge from these basins may decrease in near future. It is very important to take into account such changes while formulating any water projects in such glacierized region.

(The author, a former glaciologist at the DHM, has researched/learned about glaciers in various universities including in Japan and Germany )

Source: Spotlight, September 30, 2005, http://www.nepalnews.com.np/contents/englishweekly/spotlight/2005/sep/sep30/viewpoint.php