and statistically downscaled NEX-GDDP (0.25° resolution)
(marked in Table 3.2b of Chap. 3; 19 members) datasets.
Future projections of precipitation over the HKH, from the
three approaches along with their spatial range in ensemble
mean, are summarised in Table 11.1.
The projected precipitation changes are similar until the
2050s for both the RCP4.5 and RCP8.5 scenarios, with a
higher increase after 2050 in RCP8.5. A box-whisker analysis is provided to demonstrate the projected changes based
on CMIP5 models (Fig. 11.5). While a significant rise is
projected for annual mean rainfall, a moderate increase is
projected for the winter precipitation over the HKH. The
increase in annual mean precipitation could be in part due to
overall summertime increase in projected precipitation in the
CMIP models, which is also consistent with CORDEX
simulation (Sanjay et al. 2017). The projected changes are in
general, less than 12% for the near future under the RCP4.5
scenario. The differences in pattern and amount of projected
precipitation by end of the twenty-first century, following
RCP4.5, show similar changes as those of near future
changes projected under RCP8.5, with an increase of about
16% over the north-eastern areas of the HKH. Highresolution CORDEX and NEX simulations show value
additions in capturing the precipitation variability, as compared to the coarse-resolution CMIP5 models (Kapnick et al.
2014; Singh et al. 2017; Sanjay et al. 2017).
11.4.2 Projected Changes in Temperature
and Precipitation Extremes
Future changes in temperature and precipitation extremes
over the HKH based on the indices, such as (a) Maximum of
daily maximum temperature (TXx), (b) Minimum of daily
minimum temperature (TNn), (c) Annual total precipitation
when the daily amount exceeds the 95th percentile of
wet-day precipitation (R95p), (d) Maximum consecutive
5-day precipitation (RX5day) based on the RCP4.5 and
RCP8.5 scenarios, relative to 1976–2005, are presented in
Fig. 11.6.
The projected changes of both TXx and TNn over the
HKH indicate a tendency for extreme warm days and
extreme cold nights to become warmer in the future, with a
significant increase in TNn compared to TXx. The maxima
of TXx is projected to increase by 2.8 °C (3.4 °C) under
RCP4.5 (RCP8.5) in the near future, 4.0 °C (5.2 °C) by the
end of twenty-first century, respectively (Fig. 11.6: middle
panel). The north-western part of the HKH region is projected to experience substantial increases of TXx compared
to other areas, while pronounced warming in TNn is projected over the Eastern Himalaya and TP. In particular,
changes in TNn are projected to increase by as much as 5.5 °
C in the Eastern Himalayas and TP under the RCP8.5
scenario by the end of twenty-first century, with relatively
larger spread in RCP8.5 as compared to RCP4.5.
Future projected changes in precipitation extremes show
significant increases of R95p in both RCP4.5 and RCP8.5,
indicating the enhanced likelihood of occurrence of extreme
precipitation over the HKH. In particular, a substantial
increase in R95p is projected over the central Himalayas
during the twenty-first century. The maximum consecutive
5-day precipitation (RX5day) also shows a general rise
indicative of the future intensification of precipitation
extremes. The changes in extreme indices over HKH are
summarised in Table 11.2. In general, the MME medians
under RCP8.5 are larger as compared to those of RCP4.5,
especially for the temperature extremes. For changes in
mean precipitation, the projected median change over the
HKH is positive with large inter-model spread.
11.5 Implications of Climate Change
for Himalayan Snow and Glacier Mass
Increase of temperature and changes in precipitation patterns
over the HKH region is a major concern for the health of the
Himalayan snow cover and glaciers. This region has experienced significant melting of snow and retreat of glaciers
during the past five decades (Kulkarni and Karyakarte 2014).
While global climate change significantly affects the environment over the high mountain regions of Asia, its impact
on the Himalayan cryosphere is a major threat to the regional
water resources (ICIMOD 2007, 2011; Armstrong 2011). In
addition to global warming, the absorbing aerosols at high
elevations can also enhance the warming rate and indirectly
amplify the melting of snowpacks and glaciers (Ramanathan
and Carmichael 2008). Significant decrease of wintertime
snow over the HKH region in the recent decades is evident
from the MODIS satellite snow products which affect the
river flow regimes and water resources availability (Maskey
et al. 2011). Satellite observations of snow cover area
(NSIDC) over the HKH show large variability during the
historical period (1980–2018), with moderate decline since
2000 (Fig. 11.5: bottom panel) which is consistent with
MODIS analysis. Analysis of CMIP5 projections indicates
decrease of annual average snow over the HKH throughout
the twenty-first century, with large inter-model spread
(Fig. 11.5: bottom panel).
Heavy precipitation over the Western Himalayas (WH),
during the winter and early spring, is strongly linked to the
activity of western disturbances (WD) (Krishnan et al. 2019a,
b). High-resolution climate model projections suggest that
increasing amplitude variations of the WD in warming world
can favour enhancement of wintertime precipitation over the
Karakoram and WH (Fig. 11.7) and provide a plausible
explanation for stable snow/glacier mass in the Karakoram
214
T. P. Sabin et al.
(marked in Table 3.2b of Chap. 3; 19 members) datasets.
Future projections of precipitation over the HKH, from the
three approaches along with their spatial range in ensemble
mean, are summarised in Table 11.1.
The projected precipitation changes are similar until the
2050s for both the RCP4.5 and RCP8.5 scenarios, with a
higher increase after 2050 in RCP8.5. A box-whisker analysis is provided to demonstrate the projected changes based
on CMIP5 models (Fig. 11.5). While a significant rise is
projected for annual mean rainfall, a moderate increase is
projected for the winter precipitation over the HKH. The
increase in annual mean precipitation could be in part due to
overall summertime increase in projected precipitation in the
CMIP models, which is also consistent with CORDEX
simulation (Sanjay et al. 2017). The projected changes are in
general, less than 12% for the near future under the RCP4.5
scenario. The differences in pattern and amount of projected
precipitation by end of the twenty-first century, following
RCP4.5, show similar changes as those of near future
changes projected under RCP8.5, with an increase of about
16% over the north-eastern areas of the HKH. Highresolution CORDEX and NEX simulations show value
additions in capturing the precipitation variability, as compared to the coarse-resolution CMIP5 models (Kapnick et al.
2014; Singh et al. 2017; Sanjay et al. 2017).
11.4.2 Projected Changes in Temperature
and Precipitation Extremes
Future changes in temperature and precipitation extremes
over the HKH based on the indices, such as (a) Maximum of
daily maximum temperature (TXx), (b) Minimum of daily
minimum temperature (TNn), (c) Annual total precipitation
when the daily amount exceeds the 95th percentile of
wet-day precipitation (R95p), (d) Maximum consecutive
5-day precipitation (RX5day) based on the RCP4.5 and
RCP8.5 scenarios, relative to 1976–2005, are presented in
Fig. 11.6.
The projected changes of both TXx and TNn over the
HKH indicate a tendency for extreme warm days and
extreme cold nights to become warmer in the future, with a
significant increase in TNn compared to TXx. The maxima
of TXx is projected to increase by 2.8 °C (3.4 °C) under
RCP4.5 (RCP8.5) in the near future, 4.0 °C (5.2 °C) by the
end of twenty-first century, respectively (Fig. 11.6: middle
panel). The north-western part of the HKH region is projected to experience substantial increases of TXx compared
to other areas, while pronounced warming in TNn is projected over the Eastern Himalaya and TP. In particular,
changes in TNn are projected to increase by as much as 5.5 °
C in the Eastern Himalayas and TP under the RCP8.5
scenario by the end of twenty-first century, with relatively
larger spread in RCP8.5 as compared to RCP4.5.
Future projected changes in precipitation extremes show
significant increases of R95p in both RCP4.5 and RCP8.5,
indicating the enhanced likelihood of occurrence of extreme
precipitation over the HKH. In particular, a substantial
increase in R95p is projected over the central Himalayas
during the twenty-first century. The maximum consecutive
5-day precipitation (RX5day) also shows a general rise
indicative of the future intensification of precipitation
extremes. The changes in extreme indices over HKH are
summarised in Table 11.2. In general, the MME medians
under RCP8.5 are larger as compared to those of RCP4.5,
especially for the temperature extremes. For changes in
mean precipitation, the projected median change over the
HKH is positive with large inter-model spread.
11.5 Implications of Climate Change
for Himalayan Snow and Glacier Mass
Increase of temperature and changes in precipitation patterns
over the HKH region is a major concern for the health of the
Himalayan snow cover and glaciers. This region has experienced significant melting of snow and retreat of glaciers
during the past five decades (Kulkarni and Karyakarte 2014).
While global climate change significantly affects the environment over the high mountain regions of Asia, its impact
on the Himalayan cryosphere is a major threat to the regional
water resources (ICIMOD 2007, 2011; Armstrong 2011). In
addition to global warming, the absorbing aerosols at high
elevations can also enhance the warming rate and indirectly
amplify the melting of snowpacks and glaciers (Ramanathan
and Carmichael 2008). Significant decrease of wintertime
snow over the HKH region in the recent decades is evident
from the MODIS satellite snow products which affect the
river flow regimes and water resources availability (Maskey
et al. 2011). Satellite observations of snow cover area
(NSIDC) over the HKH show large variability during the
historical period (1980–2018), with moderate decline since
2000 (Fig. 11.5: bottom panel) which is consistent with
MODIS analysis. Analysis of CMIP5 projections indicates
decrease of annual average snow over the HKH throughout
the twenty-first century, with large inter-model spread
(Fig. 11.5: bottom panel).
Heavy precipitation over the Western Himalayas (WH),
during the winter and early spring, is strongly linked to the
activity of western disturbances (WD) (Krishnan et al. 2019a,
b). High-resolution climate model projections suggest that
increasing amplitude variations of the WD in warming world
can favour enhancement of wintertime precipitation over the
Karakoram and WH (Fig. 11.7) and provide a plausible
explanation for stable snow/glacier mass in the Karakoram
214
T. P. Sabin et al.