Geoscience Reference
In-Depth Information
Glacial melt is critical before and after the rainy season (shoulder
months) in the region, when it supplies a greater portion of fl ow in every
river from the Yangtze (which irrigates more than half of China paddy fi elds)
to the Ganges and Indus (important to the agricultural heartland of India
and Pakistan respectively). Chinese scientists have monitored more than
680 glaciers on the Tibetan Plateau and all of them are rapidly shrinking,
with heaviest losses on its southern and eastern edges. These glaciers are
not simply retreating, but they are losing mass from surface down. The ice
cover in southern and eastern plateau has shrunk more than 6% since the
1970s and the damage is still greater in Tajikistan and northern India, with
35 and 20% declines respectively over the past fi ve decades. If the current
trend holds (Tandong et al. 2009), it is believed that 40% of the plateaus
glaciers could disappear by 2050. Full scale glacier shrinkage is inevitable
and it will lead to ecological catastrophe.
The Copenhagen and Cancun Accords (CHA) in December 2009 and
2010 were accords on framework not on binding targets for reductions in
carbon dioxide emissions. The 2ºC barrier agreed at COP 15 translates into
a 2.5 Wm
-2
barrier for energy additions. However, the barrier poses a huge
dilemma for policy makers because the blanket of manmade GHGs that
surround the planet as of 2005 has already trapped 3 Wm
-2
and the barrier of
2ºC has already been exceeded by 20% (Ramanathan and Xu 2010). The most
crucial climate tipping point is the changes being felt on the plateau is the
rise of temperature of up to 0.3ºC per decade approximately three times of
global warming rate. Reduction of snow albedo by black carbon deposition
will reduce refl ectivity by 2.0 to 5.2% and thus enhancing about 70-204
mm of water equivalent runoff from a typical Tibetan glacier (Yasunari
et al. 2010). Another study by (Lau et al. 2006) indicate as a response to
radiative forcing by dust and black carbon in the Indo-Gangetic plain and
Himalayan foothills, the atmosphere over the plateau is anomalously heated
and moistened via elevated heat pump (EHP) effect. The warm and moist
atmosphere overlying the Tibetan Plateau land surface, causes a reduction
in surface sensible and latent heat fl uxes from land to atmosphere, i.e., net
heat gain by the land surface. The net heat gained is used for melting more
snow and ice over the Tibetan Plateau.
Impact on society and ecosystem
The strategic position of Tibet has became more obvious in recent years
as climate change has the potential to reduce snow pack and glacier mass
which cascade down and alter the hydrological system. Now, China has
sovereign rights on the world's largest freshwater resources outside the
Polar Regions. These water resources vulnerable to global and regional
warming are very critical for sustaining the food and water security of
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