Agriculture Reference
In-Depth Information
the availability of and access to, water resources. By the 2050s, access to
freshwater in Asia, particularly in large basins, is projected to decrease.
19.9.1 RISING TEMPERATURES
IPCC's Fourth Assessment Report (IPCC 2007a; 2007b) concludes that
there is a more than 90 percent probability that the observed warming
since the 1950s is due to the emission of greenhouse gasses from human
activity. Temperature projections for the twenty-first century suggest a sig-
nificant acceleration of warming over that observed in the twentieth centu-
ry (Ruosteenoja et al., 2003). Warming is least rapid, similar to the global
mean warming, in South-east Asia, stronger over South Asia and Eastern
Asia, and greatest in the continental interior of Asia (Central, Western, and
Northern Asia). Warming will be significant in arid regions of Asia and
the Himalayan highlands, including the Tibetan Plateau (Gao et al., 2003;
Yao et al., 2008). Based on regional climate models, it is predicted that the
temperatures in the Indian subcontinent will rise between 3.5 and 5.5ºC
by 2100, and on the Tibetan Plateau by 2.5ºC by 2050 and 5ºC by 2100
(Rupa Kumar et al., 2006). However, because of the extreme topography
and complex reactions to the greenhouse effect, even high-resolution cli-
matic models cannot give reliable projections of climate change in the
Himalayas.
Various studies suggest that warming in the Himalayas has been much
greater than the global average of 0.7 °C over the last 100 years (Dutoit
and Ziervogel, 2004; IPCC, 2007a). For example, warming in Nepal was
0.6 °C per decade between 1977 and 2000 (Shrestha et al., 1999). Warm-
ing in Nepal and on the Tibetan Plateau has been progressively greater
with elevation (Tables 4a and 4b;
Fig. 19.1)
and suggests that progressive-
ly higher warming with higher altitude is a phenomenon prevalent over
the whole of the greater Himalayan region (New et al., 2002). The major
effect on agriculture in Himalayan region is that of crop shift and under
performance of crop varieties. Apple growing area is shrinking because
chilling requirement is not being met in some areas where apple was once
successfully grown. Similar is the case with horticultural crops. Increasing
temperature has also disturbed the annual cycles of agricultural crops in
hilly areas. In many areas, a greater proportion of total precipitation ap-
pears to be falling as rain than before. As a result, snowmelt begins earlier
