Cherrapunji alone receives highest rainfall in the world around
11,000 mm per annum. These widely varying climatic
conditions in conjunction with range of topographic and soil
properties lead to a complex water resources distribution over
the country.
In India several studies have been carried out to determine the
changes in temperature and rainfall and its association with
climate change. However, investigators used different data
length and now studies have been reported using more than a
century data.
2.1 Temperature Trend in India
A study by Pant and Kumar (1997) on the seasonal and annual
air temperature of India from 1881 to 1997 shows that there has
been an increasing trend of mean annual temperature by the rate
of 0.57°C per 100 years. The trend of all India mean annual
surface air temperature anomalies is shown in Figure 1. An
analysis of temperature data of 125 stations distributed all over
India shows an increase of 0.42°C, 0.92°C and 0.09°C in annual
mean temperature, mean maximum temperature and mean
minimum temperature respectively over the last 100 years
(CWC and NIH, 2008). In a similar study, Hingane et al. (1985)
analysed long term temperature records (1901 - 1982) of 73
stations and again found increasing trend of mean annual
surface air temperature over India. It was observed that about
0.4°C warming has taken place on country scale during the
period of eight decades. It has been observed that the changes in
temperature in India/Indian-Subcontinent over last century are
broadly consistent with global trend of increase in temperature.
However, the studies carried out on regional basis show varying
trends. Hingane et al. (1985) observed that trend of increase in
mean annual temperature over the entire country was a result of
rise in the maximum temperature; but later studies carried out
by Sinha Ray et al. (1997) have shown that the changes in mean
annual temperature are partly due to rise in the minimum
temperature related to enhanced extent of urbanisation.
Thereafter findings by Mukhopadhyay et al. (1999) have
confirmed that there is clear signal of urbanisation in these
warming, i.e. that there is a steeper rise in the minimum
temperature in urban locations. Further, examination of long-
term variation in the annual mean temperature of highly
industrial and densely populated cities like Mumbai and
Kolkata has shown increasing trend in annual mean temperature
by 0.84°C and 1.39°C per 100 years, respectively (Hingane,
1995). These warming rates are much higher than the values
reported for the country as a whole.
18
Linear Trends - 057"? CAIWU ye
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e
o
A A
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^
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Temperature anomaly (C)
ca
e
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o
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un
T [ T [ T [ T | T [ T [ T [ T [ T [ T [ T | T -1.5
1890 3900 1910 1926 1930 1040 1950 1960 1973 1980 1900
Years
Figure 1. All India mean annual surface air temperature
anomalies (1881 - 1997) [Source: Pant and Kumar (1997)]
2.2 Rainfall Trend in India
Studies related to change in rainfall over India have shown that
there is no clear trend of increase or decrease in average annual
rainfall over the country (Mooley and Parthasarathy, 1984;
Sarkar and Thapliyal, 1988; Thapliyal and Kulshrestha, 1991;
Lal, 2001). The examination of trend of annual rainfall over
India has indicated that 5 year running mean has fluctuated
from normal rainfall within + one standard deviation (Thapliyal
and Kulshrestha, 1991). Summer monsoon rainfall anomalies
for all India are shown in Figure 2. Though the monsoon
rainfall in India is found to be trendless over a long period of
time, particularly on the all India scale (Mooley and
Parthasarathy, 1984), but there are pockets of significant long-
term rainfall changes (Koteswaram and Alvi, 1969; Jagannathan
and Parthasarathy, 1973; Raghavendra, 1974; Chaudhary and
Abhyankar, 1979).
A comprehensive study using the monthly rainfall data for 306
stations distributed over India was attempted by Rupa Kumar et
al. (1992). It was noticed that areas of north-east peninsula,
north-east India and north-west peninsula indicate widespread
decreasing trend in the Indian summer monsoon rainfall. On the
other hand, a widespread increasing trend in monsoon rainfall
over the west coast, central peninsula and north-west India. The
decreasing trend ranges between -6 to -8% of the normal per
100 years while the increasing trend is about 10 to 12%.
= 3
fe
LLL [TAT [TT Ire
c
Toren d inn n n n a na na aa
Ruinfull A nomaly (*c of meant
3870 1880 1000 2900 1910 1820 1630 ME 1950 1960 1973 1908 10900 — 2000
Ds
E
=
E
Years
Figure 2. All India summer monsoon rainfall anomalies (1871 -
1999) [Source: Lal (2001)]
A warmer climate may lead to intensification of the
hydrological cycle, resulting in higher rates of evaporation and
increase of liquid precipitation. These processes, in association
with a shifting pattern of precipitation, may affect the spatial
and temporal distribution of runoff, soil moisture, groundwater
reserves etc. and may increase the frequency of droughts and
floods. Increase in extreme climatic events will be of great
consequence owing to the high vulnerability of the region to
these changes.
3. SCENARIO DEVELOPMENT
In order to predict the future change in temperature as well as
temporal and spatial variability in monsoon rainfall over India,
many studies have been carried out. In one such analysis, Lal
(2001) developed the four SRES emission scenarios based on
the data generated in numerical experiments with Atmosphere
and Ocean coupled Global Circulation Model of the
CCSR/NIES, Japan. It was projected that over the inland
regions of the Indian sub-continent, the mean surface
temperatui
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