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New Proofs of Effect of Climate Change in Nepal

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  • Mike Neuman
    New Proofs of Effect of Climate Change in Nepal By DR RIJAN BHAKTA KAYASTHA Like in many other countries, now-a-days, climate change has become a common topic
    Message 1 of 1 , Oct 5, 2005
      New Proofs of Effect of Climate Change in Nepal
      By DR RIJAN BHAKTA KAYASTHA

      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 )

      http://www.nepalnews.com.np/contents/englishweekly/spotlight/2005/sep/
      sep30/viewpoint.php
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