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The Changing Himalayas
region. Even more importantly, they contribute about 70% of Based on regional climate models, it is predicted that the
the flow in the dry season (Alford 1992). In western China, temperatures in the Indian sub-continent will rise between
glacial melt provides the principal water source in the dry 3.5 and 5.5ºC by 2100, and on the Tibetan Plateau by
season for 25% of the population (Xu 2008). The Indus 2.5ºC by 2050 and 5ºC by 2100 (Rupa Kumar et al.
Irrigation Scheme in Pakistan depends 50% or more on 2006). However, because of the extreme topography
runoff originating from snowmelt and glacial melt from the and complex reactions to the greenhouse effect, even high
eastern Hindu Kush, Karakoram, and western Himalayas resolution climatic models cannot give reliable projections of
(Winiger et al. 2005). climate change in the Himalayas.
Various studies suggest that warming in the Himalayas has
Observed and Projected Effects been much greater than the global average of 0.74°C
of Climate Change
over the last 100 years (IPCC 2007a; Du et al. 2004).
For example, warming in Nepal was 0.6°C per decade
Climate change is currently taking place at an
between 1977 and 2000 (Shrestha et al. 1999). Warming
unprecedented rate and is projected to compound the
in Nepal and on the Tibetan Plateau has been progressively
pressures on natural resources and the environment
greater with elevation (Tables 4a and 4b and Figure 1),
associated with rapid urbanisation, industrialisation, and
and suggests that progressively higher warming with higher
economic development. It will potentially have profound
altitude is a phenomenon prevalent over the whole of the
and widespread effects on the availability of, and access
greater Himalayan region (New et al. 2002) (Figure 2).
to, water resources. By the 2050s, access to freshwater in
Asia, particularly in large basins, is projected to decrease. In many areas, a greater proportion of total precipitation
appears to be falling as rain than before. As a result,
snowmelt begins earlier and winter is shorter; this affects
Rising Temperatures
river regimes, natural hazards, water supplies, and people’s
IPCC’s Fourth Assessment Report (IPCC 2007a; 2007b)
livelihoods and infrastructure, particularly in basins such as
concludes that there is a more than 90% probability that the
the Tarim, which is dependent upon glacial melt in summer.
observed warming since the 1950s is due to the emission
The extent and health of high altitude wetlands, greenwater
of greenhouse gases from human activity. Temperature
flows from terrestrial ecosystems, reservoirs, and water flow
projections for the 21
st
Century suggest a significant
and sediment transport along rivers and in lakes are also
acceleration of warming over that observed in the 20
th

affected.
Century (Ruosteenoja et al. 2003). In Asia, it is very likely
that all areas will warm during this century. Warming
Precipitation Trends
is least rapid, similar to the global mean warming, in
Southeast Asia, stronger over South Asia and Eastern Asia, Long-term paleo-climatic studies (e.g. ice core studies on
and greatest in the continental interior of Asia (Central, the Tibetan Plateau) show that both wet and dry periods
Western, and Northern Asia). Warming will be significant have occurred in the last millennium (Tan et al. 2008, Yao
in arid regions of Asia and the Himalayan highlands, et al. 2008). During the last few decades, interseasonal,
including the Tibetan Plateau (Gao et al. 2003; Yao et al. interannual, and spatial variability in rainfall trends have
2006). been observed across Asia. In the Himalayan region, both
increasing and decreasing trends have been detected.
Increasing trends are found on the Tibetan Plateau in the
northeast region (Zhao et al. 2004) and eastern and central
parts (Xu et al. 2007), while the western Tibetan region
Figure 1: Dependence of warming on elevation on the Tibetan
exhibits a decreasing trend; northern Pakistan also has an
Plateau (Liu and Chen 2000)
increasing trend (Farooq and Khan 2004); Nepal showed
no long-term trend in precipitation between 1948 and
1994 (Shrestha et al. 2000; Shrestha 2004).
Elevation
T
emperature T
Temperature trend
A decrease in monsoon precipitation by up to 20% is
projected by the end of the century in most parts of Pakistan
rend (°C/decade)
and in south-eastern Afghanistan. A similar reduction in
precipitation is projected for the southern and eastern
Elevation, m
Tibetan Plateau and for the central Himalayan range.
Elevation, m
Increases in the range of 20 to 30% are projected for the
western Himalayan Kunlun Shan range and Tien Shan
range (Rupa Kumar et al. 2006).
4
Number of Stations
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