Future Sustainability Challenges in Hindu Kush-Himalaya - Impact of Global Changes on Mountains: Responses and Adaptation - page 237

uniformly to observed changes in climate; latest climate studies provide
no meaningful insight into the signifi cance of recently observed changes
in climate compared to the natural variability of the region's climate (NAS
2012); and incomplete understanding of the processes affecting Himalayan
glaciers under the current climate, make any projection on the Himalayan
glaciers unclear.
The rate of retreat and growth of individual glaciers is highly dependent
on glacier characteristics and location; small glaciers at low elevation
and with little debris cover are the most vulnerable (NAS 2012). There is
evidence of glacier retreat in the eastern and central Himalayas with rates
accelerating over the past century, while glaciers in the western Himalayas
appear to be more stable overall, glaciers around the Karakoram region
show complex behavior and some have advanced and thickened (Gardelle
et al. 2012, Scherler et al. 2011) indicating an apparently atypical behavior
that has prevented drawing conclusion about the future state of Karakoram
glaciers (Perkins 2012) (Fig. 10.7). Gangotri Glacier has a long record of
terminus fl uctuation with multidecadal terminus retreat rate variations
since the 19th century. The retreat has stopped in the last decade (Fig. 10.8)
(Kargel et al. 2011).
Black carbon affecting glaciers and Asian monsoon
Atmospheric loading of aerosol in the form of a brownish haze known as
Atmospheric Brown Clouds (Ramanathan et al. 2005), from anthropogenic
activities has signifi cantly increased, making the Indo-Gangetic Plain one
of the most polluted region in the world (Fig. 10.9). Black Carbon (BC) from
the incomplete combustion of fossil fuels, biofuels, and biomass is a key
component of ABC that strongly absorbs solar radiation contributing to
increase in average global temperature (Fig. 10.10), and widely known to
have an effect on snow/ice albedo that lead to surface dimming, especially
strong in sensitive regions like the HKH (USEPA 2011). Recent studies have
shown that black carbon because of its ability to heat the atmosphere, can
affect the regional and global water cycles by altering the radiation balance
of the Earth's atmosphere and surface, and modulating cloud and rain
formation processes (Lau et al. 2010, Ramanathan et al. 2005, Rosenfi eld
et al. 2008).
At a regional level, changes in monsoon such as weakening of summer
monsoons over the past 50 years, a decreasing trend in the length of the
monsoon (Dash et al. 2009, Ramesh and Goswami 2007), a model output
indicate reduced rainfall over India, with a small increase over the Tibetan
Plateau (Meehl et al. 2008). A consistent fi nding shows that aerosols can
substantially infl uence the timing and intensity of the South Asian monsoon
(NAS 2012) by the mixture of dust (desert dust) and BC in the deep aerosol