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Climate change and related impacts over the Indian Himalayan Region (IHR) remains poorly quantified. The present study reviews observed and modelled changes in the climate, cryosphere and impacts related to hazards, agriculture and ecosystems. An increasing temperature trend over the IHR is reported, which over a few locations is found to be higher than the global average. For precipitation, a complex and inconsistent response with considerable variation in the sign and magnitude of change is observed. Future projections show significant warming. Climate-driven changes and impacts are clearly observed. Snow cover has declined since the 1960s, with an enhanced decreasing trend during the 1990s and variable trends since 2000. Glaciers are losing mass and retreating at varying rates since the early 20th century, with an exception over the Karakoram region. An observed heterogeneous response of glaciers to atmospheric warming is controlled by regional variations in topography , debris cover, circulation and precipitation. Initial assessments of permafrost extent of 1 million km 2 across the IHR roughly translate into 14 times the glacier area. Extreme floods represent the most frequent natural disaster in the IHR. Studies have highlighted the significant threat from glacial lakes. Landslides occur in combination with heavy rainfall and flooding, with poor land-use practices such as road-cutting and deforestation being additional drivers. Climate change has also stressed traditional subsistence agriculture and food systems. Improving systematic and coordinated monitoring of climate and related impacts is crucial to contribute to effective climate change adaptation and response strategies.
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Climate change, cryosphere and impacts in the
Indian Himalayan Region
A. P. Dimri1,*, S. Allen2,3, C. Huggel2, S. Mal4, J. A. Ballesteros-Cánovas5,
M. Rohrer5,6, A. Shukla7, P. Tiwari8, P. Maharana1, T. Bolch9, R. J. Thayyen10,
M. Stoffel5,11,12 and Aayushi Pandey1
1School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110 067, India
2Department of Geography, University of Zurich, Switzerland
3Institute for Environmental Sciences, University of Geneva, Switzerland
4Department of Geography, Shaheed Bhagat Singh College, University of Delhi, Delhi 110 017, India
5Institute for Environmental Sciences, University of Geneva, Switzerland
6Meteodat GmbH, Zurich, Switzerland
7Ministry of Earth Sciences, New Delhi 110 003, India
8Department of Geography, Kumaon University, Nainital 263 001, India
9School of Geography and Sustainable Development, University of St Andrews, Scotland, UK
10National Institute of Hydrology, Roorkee 247 667, India
11Department of Earth Sciences, University of Geneva, Switzerland
12Department of F.-A. Forel for Environmental and Aquatic Sciences, University of Geneva, Switzerland
Climate change and related impacts over the Indian
Himalayan Region (IHR) remains poorly quantified.
The present study reviews observed and modelled
changes in the climate, cryosphere and impacts re-
lated to hazards, agriculture and ecosystems. An in-
creasing temperature trend over the IHR is reported,
which over a few locations is found to be higher than
the global average. For precipitation, a complex and
inconsistent response with considerable variation in
the sign and magnitude of change is observed. Future
projections show significant warming. Climate-driven
changes and impacts are clearly observed. Snow cover
has declined since the 1960s, with an enhanced de-
creasing trend during the 1990s and variable trends
since 2000. Glaciers are losing mass and retreating at
varying rates since the early 20th century, with an
exception over the Karakoram region. An observed
heterogeneous response of glaciers to atmospheric
warming is controlled by regional variations in topo-
graphy, debris cover, circulation and precipitation.
Initial assessments of permafrost extent of 1 million
km2 across the IHR roughly translate into 14 times the
glacier area. Extreme floods represent the most fre-
quent natural disaster in the IHR. Studies have high-
lighted the significant threat from glacial lakes.
Landslides occur in combination with heavy rainfall
and flooding, with poor land-use practices such as
road-cutting and deforestation being additional driv-
ers. Climate change has also stressed traditional
subsistence agriculture and food systems. Improving
systematic and coordinated monitoring of climate
and related impacts is crucial to contribute to effective
climate change adaptation and response strategies.
Keywords: Climate change, cryosphere, glacier, per-
mafrost, run-off.
MOUNTAINS roughly cover 25% of the Earth’s surface
with about 915 million people or 12% of the global popu-
lation living in mountain regions, and 90% thereof in
developing countries. Much larger number of people,
however, benefit from sustenance provided by mountains
to downstream regions. Associated rivers fed by snow
and icemelt critically contribute to life-support systems2–4
as well as the social and economic welfare5. Mountain
systems are, highly sensitive to climatic variability and
change6–9. This is especially true for the mountain cryo-
sphere with respect to glaciers, snow and permafrost – all
interacting and responding to climate in a distinct way.
Recent global assessments from the Intergovernmental
Panel on Climate Change (IPCC)10–12 have documented
observed and projected impacts of climate change on the
cryosphere13,14. The recent Hindu Kush Himalayan
Monitoring and Assessment Programme (HIMAP)15 report
provides comprehensive information over the region. Yet
mountain regions, and in particular the high mountains,
suffer from the scarcity of observational data, and climate
models are challenged by the complexities of mountain
climate, which is strongly controlled by topography.
The Himalaya and its sub-regions prominently feature
in this debate because of their importance for the vast
number of people inhibiting these and the downstream
regions (Figure 1). This is in contrast to the paucity of
data and information available over the region. While the
status and changes in the glaciers in Himalaya have been
the focus of several studies in recent years15–17, some
CURRENT SCIENCE, VOL. 120, NO. 5, 10 MARCH 2021 775
other groups have examined the hydrology and associated
changes in the region18–20. Yet, the broader impacts of
changes in climate and cryosphere on ecosystems, people
and economy are either scarcely documented or quantified.
The Government of India (GoI) recognized this chal-
lenge, with one of the National Missions of the National
Action Plan on Climate Change (NAPCC) focusing on
sustaining the Himalayan ecosystem. For the 12 States
falling within the Indian Himalayan Region (IHR), State
Action Plans on Climate Change have been developed for
implementation. Scientific evidence on observed and pro-
jected climate, cryosphere changes and associated im-
pacts is crucial in this context. Here we provide a review
on the current state of knowledge on the IHR, focusing on
climate (i.e. temperature and precipitation), and all com-
ponents of the cryosphere (i.e. glaciers, snow and perma-
frost). In terms of impact, we concentrate on glacier lake
outburst and other floods, landslides, hydrological
changes and briefly on related agriculture, ecosystem and
livelihood impacts. Our primary focus is the IHR, but for
some cases such as for the climate, we need to extend
beyond the IHR due to the importance of the context of
the greater Himalayan region.
Changes in climate and cryosphere over the
Indian Himalaya
Present and future warming
Warming over the Himalaya has exceeded the global
average rise in temperature11 having different annual/
seasonal warming rates over its different sub-regions.
Increasing temperature trends of 0.12°C/yr (ref. 21) and
0.4°C/yr (ref. 22) are reported over the middle Mountains
and Himalaya respectively. An increase of 0.03°C/yr
from 1985 to 2002 in Bhutan in the Eastern Himalayas is
also reported23. Pre-monsoon warming of 2.7°C/yr due to
aerosol interaction has been found along the Himalayan
slopes4. Higher winter warming is reported over Nepal
Himalaya21, western/northwestern Himalaya24,25, upper
Indus basin (UIB)26 and the Tibetan Plateau
27. The in-
creasing trend in maximum temperature is higher than
that of minimum temperature over the western Hima-
laya25,28, but increasing warm nights over western Hima-
laya28 are also an indication of the rising trend in
minimum temperature. A greater warming rate at higher
elevation zones over Nepal Himalaya21 and greater warm-
ing with increasing altitude over India and Pakistan
Himalaya24 has been documented. While more warming
over higher mountains than low elevations at the same
latitude has been reported29, more recent research has
found that such elevation dependent warming (EDW) is
not consistent across different mountainous regions, with
the Tibetan Plateau being a region where EDW has been
found30. Regional heterogeneity of EDW is considered to
be a function of various physical temperature-relevant
processes such as snow albedo and surface-based feed-
backs, water vapour changes and latent heat release, aero-
sols and others31. Generally, decreasing number of
meteorological stations with increasing elevation limits
better understanding in the IHR.
Future climate projections from the Coordinated
Regional climate Downscaling Experiment-South Asia
(CORDEX-SA) show an underestimation of mean
monthly or annual temperature. However, winter warm-
ing trend over the IHR has been observed32. Increasing
maximum temperature during winter reported from vari-
ous models33 agrees with earlier findings
34. In addition,
minimum and maximum temperatures show a decreasing
trend with elevation. CMIP3 and CMIP5 models studies
for the period 1960–2000 suggest an increase in annual
average temperature over eastern (2.5°–4°C) and western
Himalaya (2.8–4.5°C) by the end of 21st century35. Over
the Tibetan Plateau a projected rise of 4°C is estimated
by 2100 compared to 1950 (ref. 25).
The projected increase in winter temperature from the
present to the end of 21st century is reported to be 5.4°C
under RCP8.5°C over Karakoram and Northwest Hima-
laya36. The increase of projected minimum temperature
and warm nights over the southern Koshi basin in the
Nepal Himalaya37 and UIB in the Western Himalaya, will
be higher compared to the lower Indus basin (LIB)34.
Various modelling studies have shown amplified warm-
ing with altitude during winter over the Tibetan
Plateau25,30 and the IHR
38–40 under increasing CO2 con-
centrations. Supplementary Figures 1–3 show average
mean, minimum and maximum temperature respectively,
over the IHR based on model results. These results indi-
cate that projected climatological mean and trends of
temperature are increasing, thus the climate is moving
towards a warmer regime.
Based on these studies, it can be summarized that both
observational and modelling studies show that there are
warming trends, although with different rates, along and
across the IHR.
Present and future precipitation
The Himalayan folded mountain structure leads to mountain
lee wave and Bergeron’s seeder-feeder mechanisms41,42.
Moist orographic interactions modulate precipitation dis-
tribution over the IHR43–45. Orographic interactions block
and force moisture upwards resulting in strong vertical,
horizontal and slope-wise precipitation gradients42,46–48.
Windward sides receive higher precipitation than leeward
sides49. The uneven distribution of rainfall in the moun-
tains results in differential rainfall trends within small
distances, and leads to floods and droughts45. Eastern and
Central Himalaya receive 80% of the annual precipitation
due to the Indian summer monsoon (ISM), whereas the
western Himalaya receives ~30% due to western distur-
bances (WDs)16,50 which, however, are embedded in the
Figure 1. Location of study area with important places referred to the paper. The red line indicates the international boundary of India, while the
grey lines indicate the boundaries of Himalayan states in India. J&K, Jammu and Kashmir; HP, Himachal Pradesh; UK, Uttarakhand; AP,
Arunachal Pradesh. State of J&K and HP belongs to western Himalaya; UK and Nepal to central Himalaya and SK, Bhutan and AP to eastern
Himalaya. Various locations are as well marked for better understanding of the region. The background elevation (ASTER GDEMV2) is obtained
Figure 2. Variation in observed monsoonal precipitation with
elevation. The bars show the number of grid points at each 1000 m
elevation bins67.
Indian winter monsoon (IWM)34,44,51. The precipitation
relevant east–west divide is around the Sutlej valley in
the western Himalayas. Catchments towards the east
(west) get 70% (50%) annual precipitation due to ISM49.
Figure 2 shows a modelled elevation-dependent precipita-
tion distributions. It clearly shows that higher elevations
receive precipitation within a smaller range and vice versa.
The increase of extreme rainfall events leading to
floods seems to be heterogeneous across India, showing a
slight decrease in the central and northern parts of the
country, and an increase of extreme events in the east and
North East of India52. An increase of cloudburst events
has been furthermore recorded in the Central Himalaya53,
although limitations associated with the length of obser-
vations have to be considered. Increases in extreme rain-
fall events during the last decades have been associated
with an increase in sea surface temperature over the tro-
pical Indian Ocean54.
Observational studies show no clear seasonal and
annual precipitation trends over the IHR, but regionally
some changes are observed. For instance, increased
CURRENT SCIENCE, VOL. 120, NO. 5, 10 MARCH 2021 777
Figure 3. Summary of 164 glaciological, geodetic, and modelling estimates of rates of glacier mass change (m w.e./yr) by
glacier region. The arithmetic average of data from all studies pre and post-2000 is shown by the shading of half circles (pre-2000
left, post-2000 right), together with the number of studies available for each period; periods without data are coloured in grey. A
histogram of all reported regional mass change rates is given in the upper right (Source: Bolch et al.219).
average precipitation and significantly decreased light
precipitation events are reported for the Hindu-Kush Hima-
laya (HKH) and the central Indian region55, while in-
creased winter precipitation is noted for the Karakoram35.
Increased precipitating WDs56; increasing (decreasing)
seasonal winter (summer) precipitation and mild increase
in annual precipitation have been found over the Beas ba-
sin in Himachal Pradesh57, and the Koshi basin in the
Nepal Himalaya46,47, whereas decreasing monsoonal pre-
cipitation has been observed over the Uttarakhand region,
Central Himalaya45,58. For the Eastern Himalaya annual
precipitation is declining, but precipitation has increased
during the later phase of the monsoon period58,59.
Changes in precipitation extremes are challenging to
detect in sparsely equipped mountain areas, but have been
found for a number of regions: over the western Hima-
laya increasing extreme precipitation up to 3000 m and
decreasing at higher elevations can be observed60. Also,
decreased monsoon precipitation over the Hindu-Kush
and the western Himalaya, and increasing extreme preci-
pitation over the Karakoram, the western Himalaya and
UIB have been reported55,61–63, with a periodicity of 2.7
years in extremes59.
Regional climate models (RCMs) are not capable of
accurately resolving the precipitation distribution over
the IHR41,64, being sensitive to horizontal resolution,
variable topography and heterogeneous land use43,44, local
atmospheric circulation44 and extremes65. Improved para-
meterization is able to reproduce extreme wet and dry
years44,64, and precipitation (snow cover) over the foot-
hills (central Himalayas), but underestimates snow cover
over the eastern Himalaya66. A wet bias over the western
Himalaya64 and elevation dependency of summer precipi-
tation can be observed67. Projected increased monsoonal
precipitation68,70–72, with increased extreme events35,63,69
and decreased number of rainy days69, is predicted for the
end of the 21st century. Increased converging moisture
from the Arabian Sea leading to increased ISM precipita-
tion over western Himalaya is projected68,69 whereas a
few researchers reported no specific precipitation
trends63. Global climate model (GCM) based projections
show increased summer (23–35%) and winter (17–28%)
precipitation along with precipitation extremes over east-
ern Himalaya. RCMs depict decreased (increased) pro-
jected summer rainfall over the Central (eastern and
western) Himalaya35,68,73. A model-based distribution of
monsoonal precipitation averaged over the IHR is shown
in Supplementary Figure 4.
Based on the above discussion of precipitation distribu-
tion and variability, higher elevation regions have a high-
er drying rate than the lower elevation regions. This is
primarily due to orographic forcing in association with
increased surface warming. However, in the IHR, the
coupling between moisture and temperature is complex
and the primary precipitation mechanisms (and thus asso-
ciated precipitation) are not simple to characterize.
Glacier change
Estimates of glacier coverage in the IHR vary from
~30,000 km2 (ref. 74), ~25,000 km2 (ref. 75) to
~14,000 km2 based on the most recent version of the
Randolph Glacier Inventory76. These differences could be
attributed to the fact that different datasets and varying
methodologies were employed, and monitoring was done
over sub-regions with disputed boundaries. Many glaciers
in the Himalaya are heavily debris-covered at their
tongues. Debris coverage varies between ~5% and ~15%
of the glacier area in different regions of the Himalaya77.
Thick debris cover significantly reduces ice melt and
many debris-covered glacier tongues are relatively sta-
ble78,79. However, these glaciers are also significantly
losing mass80,81. Compilations pertaining to temporal
variations suggest that glaciers in the Himalaya have on
the average been degenerating at varying rates since the
19th century, with an exception of the Karakoram gla-
ciers which have shown long-term irregular behav-
Regional estimates of glacier length changes suggest
that the western Himalayan glaciers (Jammu and Kash-
mir, Himachal Pradesh) experienced enhanced retreat
compared to those in the Central (Uttarakhand) and east-
ern Himalaya (Sikkim)46,79,85. However, results of snout
monitoring might be biased towards larger glaciers as
area change estimates show similar or even higher loss
rates in Sikkim compared to Himachal Pradesh86–88. Gla-
ciers in the Central (Garhwal) Himalaya show average
shrinkage rates87–89, while small glaciers in the eastern
parts of Jammu and Kashmir (Ladakh) experience rela-
tively little recession90. Kraaijenbrink et al.91 have shown
that a global temperature rise of 1.5°C will lead to a
warming of 2.1° ± 0.1°C in High Mountain Asia
(HMA), and that about 64 ± 7% of the present-day ice
mass stored in the HMA glaciers will remain by the end
of the century.
Glaciers in the Karakoram have shown individually
contrasting behaviour, but on average stable areas92,93,
and balanced mass budgets since the 1970s94–96. Many
glaciers in the northwestern IHR are of surge type; hence
they periodically speed up and advance rapidly83,92,97,98.
Surface velocity measurements also reveal that glaciers in
the Karakoram region are almost active at their snouts.
The concentration of stagnant glaciers is highest in the
Central and eastern Himalaya and can be related to local
topography and the presence of debris cover79,99,100. In
contrast to the Karakoram, clear mass loss was found for
almost all other Himalayan ranges. In situ measurements
indicate moderate mass loss until the ~mid 1990s and an
increased mass loss thereafter16. However, glaciers in
northern Himachal Pradesh (Lahaul-Spiti) might have
experienced a period of only slight mass loss during the
1990s (ref. 101). The highest loss rates after ~2000 are
seen in the western Himalaya (>–0.6 m w.e. a1) followed
by the eastern Himalaya including the ranges of Arun-
achal Pradesh (0.5 to –0.6 m w.e. a1), and the least mass
loss was found in the central Himalaya (Garhwal in Utta-
rakhand) (~0.4 m w.e. a1)17,102. However, large variabi-
lity also exists in glacier mass balances. The observed
heterogeneity in the response of glaciers to climate
change may be attributed to differences in topography,
debris cover and meteorological mechanisms which are
regionally unique47,79,103–105.
Widespread deglaciation in several regions has led to
glacier fragmentation, vanishing of smaller glaciers, forma-
tion and enlargement of glacial lakes and increase in
supraglacial debris cover16. Figure 3 shows the distribution
of modelling estimates of rates of glacier mass change.
Snowcover change
Snow, being one of the most sensitive natural resources,
warrants comprehensive temporal assessment of various
metrics at different scales. At global scale due to its highly
reflective nature, snow greatly impacts climate variations,
surface hydrology and energy exchange5,106. At the basin
scale, seasonal snow cover acts as an important short-
term freshwater storage and key input to glacier mass
balance, volumetric meltwater run-off modelling and
snow hazard prediction studies10,19,107–114. Despite its dis-
tinct water storage characteristics and immense societal
as well as climatic significance, research on snow cover
dynamics in the IHR has lagged behind, with limited re-
gional115–117, and even fewer basin-scale studies118–120.
Data on snow-cover changes over the IHR are scarce.
Studies that have examined various mechanisms and
processes using satellite-derived snow-cover estimates
over the IHR have emphasized the temporal variability of
snow cover121–124. Studies reporting pre-2000 snow-cover
changes in the IHR, though rare, in general point towards
a decline after the 1960s which accentuated towards the
decade of the 1990s and was also synchronous with an
increase in snow melt115,124,125 (Figure 4). Post-2000, sev-
eral studies have reported varying rates of snow cover
depletion for different regions of the IHR (Figure 4). Us-
ing the MODIS eight-day-snow cover product, Gurung et
al.116 reported an increasing snow-cover trend of 10–12%
CURRENT SCIENCE, VOL. 120, NO. 5, 10 MARCH 2021 779
in the eastern and western Himalaya, and a declining
trend of 12–14% for the Central region of HKH between
2000 and 2010. For almost the same time period (2000–
2011) but at a basin-scale, an increasing snow-cover
trend has been found for the Indus basin while decreasing
trends have been reported for the Ganga and Brahmaputra
basins117. Contrasting results have also been reported by
Rathore et al.120 for the three sub-basins of Ganga river,
where they found a statistically insignificant increase of
approximately 1–2% in snow cover in the Central Hima-
laya (Uttarakhand region). Contrary to Singh et al.117, but
in agreement with Gurung et al.116, the study by Mukho-
padhyay119 shows that snow cover in the Brahmaputra basin
increased by ~32% from 1980 to 2010 and remained
stable from 2000 to 2010 (Figure 4). This is attributed to
the recent increase in the amount of moisture supplied by
moist air mass that incurs into the Brahmaputra valley.
A number of snow-cover monitoring studies have been
carried out in the western Himalayan region at the basin
scale for varying time-periods ranging between 1988 and
2012 (refs 118, 126–129). Studies spanning the extended
western Himalayan regions (including Karakoram) report
overall increasing or stable snow cover trends since 2000
(refs 128, 129) except for a decreasing winter snow-cover
trend for the UIB118. However, studies specifically from
the IHR reveal a secular decline in snow-covered
areas126,127 (Figure 4).
Permafrost is sediment or bedrock that remains frozen for
at least two consecutive years. It mainly occurs in the
Arctic130 and high mountain areas131–133. It encompasses
around 25% of the land mass of the Northern Hemis-
phere134. A number of studies have shown that permafrost
has thawed in the Northern Hemisphere during the past
couple of decades135–138. However, permafrost studies are
sparse in the HKH region in general and the IHR in par-
ticular139. In the IHR, cryospheric studies are largely
Figure 4. Snow cover trends over the Indian Himalayan region (IHR)
in different time frames. Pre-2000 snow cover studies are rare,
however, report a generalized decline in snow cover. Post-2000 studies
reveal variable snow cover dynamics in different Himalayan regions.
WH, western Himalaya; UIB, Upper Indus Basin; CH, central
Himalaya; EH, eastern Himalaya; SCE, Snow Cover Extent.
focused on snow and glaciers due to their visible impacts
on the environment and resources. More recently, with
increasing human stressors and a changing climate,
research has begun to focus on the finer details of water
resource dynamics in the IHR, to include first studies on
subsurface permafrost. Of late, research on permafrost is
being initiated by national and international agencies in
the IHR. Conclusive evidence of permafrost in the IHR
was first gathered from Tso Kar lake area (cold-arid re-
gions of Jammu and Kashmir) in 1975–76 from a study
conducted by the Geological Survey of India (GSI)140.
Boreholes drilled up to 29 m depth had many ice layers
interspersed with sandy gravel layers, and annual average
temperature of –2°C indicated permafrost area across
~20 km2. An initial modelling assessment on a regional
scale suggests that the permafrost area in the HKH region
could extend up to 1 million km2, which roughly trans-
lates into 14 times the area covered by glaciers139. Studies
on rock glacier distribution (a surface landform indicative
of permafrost) have also been carried out in the recent
past, suggesting that the lower limit of permafrost in the
region lies within 3500–5500 m asl (refs 141). Allen et
al.142 suggested a permafrost spread of 420 km2 in Kullu
district, located in north-central parts of Himachal Pra-
desh. The cold-arid region of the eastern parts of Jammu
and Kashmir has reported sporadic occurrence of perma-
frost and associated landforms139 with sorted patterned
ground and other periglacial landforms such as ice-cored
moraines. Catchment-scale studies suggest that the
ground ice melt component may be a critical water source
during dry years in the cold-arid regions of Jammu and
Kashmir143. This region has large areas of high-altitude
wetlands and lakes, and the studies indicated phases of
permafrost growth during low lake levels, especially
since 5 kyr BP. Continuous development of permafrost
mounds and thermokarst features is also inferred during
the last 60 years144. These studies have firmly established
significant permafrost coverage in high mountain areas of
the IHR. As glaciers and snow cover are shrinking across
most parts of the IHR, in response to changing climate,
permafrost areas are also expected to respond in a compa-
rable manner as evident from other similar cryospheric
areas globally. Using modelling strategies, Schaphoff et
al.145 have shown that vegetation responds more rapidly
to warming of the permafrost zone than soil carbon pools
due to long time lags in permafrost thawing. Possible
permafrost thaw-related impacts have been inferred from
other areas which include changing frequency and spatial
distribution of landslides, changes to vegetation and run-
off patterns, changes in water quality and sediment load
in rivers, with important implications for populations de-
pendent on these high-altitude ecosystems139. However,
long-term monitoring and evidence of such impacts in the
IHR are generally lacking. For example, landslides are
widespread across the IHR, but interestingly, large high
mountain slope failures are rarely documented, and as yet
there is no evidence to suggest that thawing of permafrost
has any notable influence on mass movement activity in
the IHR.
Given that permafrost covers an area 14 times larger
than that covered by glaciers, the potential effects of
permafrost melting in the IHR need further studies to
better understand both immediate and long-term conse-
Upstream and downstream impacts
Glacier lake outburst floods
Glacial lakes are a common feature in high mountain
regions and are closely associated with regional patterns
of glacial response to climate change111, 146. A first com-
prehensive inventory of glacial lakes led by ICIMOD
(with support of various institutions) revealed around
8790 glacial lakes (1999–2003) across the broader HKH
region, from which 1900 were located in the IHR (ref.
147 and references cited therein). In their studies in the
IHR, Worni et al.148 and Fujita et al.149 identified 251 and
500 glacial lakes respectively (>0.01 km2 area). This dis-
crepancy in the results can be attributed to the different
thresholds (minimum lake size) and methods (manual or
semi-automated lake detection) adopted for the mapping
of glacial lakes150; Table 1 and Supplementary Table 1.
Furthermore, these discrepancies highlight the difficulties
in directly comparing different inventories in the region,
leading to uncertainties in the baseline data that feed into
related adaptation planning and risk reduction strategies.
Across the IHR, the number and area of glacial lakes
have rapidly increased as a result of a warmer climate
during the last century146,147,151,152. According to Nie et
al.150, the number and area of glacial lakes in the IHR on
an average has increased by about 8.8% and 14% respec-
tively, during 1990–2015. Glacial lakes connected or lo-
cated close (less than 2 km) to the glaciers particularly
showed enhanced expansion (about 50%)151,153, and con-
tributed most (about 83%) to total growth of glacial lakes
during 1990–2015 in the region150,151. Furthermore, high-
er growth of glacial lakes is observed on southern slopes
of the Himalaya compared to the northern slopes. Longi-
tudinally, highest growth has been observed in central
Himalaya, followed by eastern Himalaya, while expan-
sion has been slowest in the western Himalaya146,150. The
emergence and expansion of new glacial lakes have been
mostly concentrated at higher elevations (4800–5700 m),
and observed even at 5900 m, indicating enhanced warm-
ing at higher elevations150. Local assessment studies in
the IHR, e.g. Himachal Pradesh154, Chandra basin, Hima-
chal Pradesh155,156, Chandra-Bhaga basin, Himachal
Pradesh157,158, Uttarakhand159; Alaknanda basin, Uttarak-
hand160; Dhauli Ganga basin, Uttarakhand161; Sikkim
Himalaya162–164 confirm the emergence and rapid expan-
sion of glacial lakes across the entire region. While lakes
that are no longer fed by glacier melt have remained nearly
unchanged in the region150,151,153, such lakes can still pose
a substantial threat to downstream communities159. For
example, disconnected lakes at the side of a glacier (ice-
marginal lakes) can become unstable where adjacent
glaciers are losing mass and thereby removing support
from the dam159,165. The increasing potential of large ice
and rock mass failures into lakes, leading to glacier lake
outburst floods (GLOFs), has been demonstrated in the
IHR by Allen et al.165, and hence, an increasing trend in
GLOF potential is expected over the 21st century.
In the larger HKH region, the frequency of GLOFs is
reported by some authors to have increased around the
mid-20th century152,166,167. However, in the IHR, GLOFs
have been rarely reported168, except for the Chong
Kumdam GLOFs (1929, 1932, 1933 and 1939) in the
UIB169,170 and the devastating Chorabari GLOF (2013)
above Kedarnath in Uttarakhand165,171–173. Coxon et al.172
and Sangode et al.
173 described evidence of palaeo-
GLOFs based on studies of sediment deposits in parts of
western Himalaya (Lahaul and Ladakh). Although no
GLOF events have been recorded in the eastern Himalaya
(Sikkim), field evidence and local knowledge support
their past occurrences164. The relative lack of GLOF evi-
dence may be explained by the fact that the overall area
of glacial lakes and their expansion is comparatively low-
er in the IHR than other Himalayan regions, e.g. Nepal,
Tibet and Bhutan146,150. However, there may also be
issues of under-recording, with some past GLOF events
being recorded as flash-flood events. Several studies pro-
vide assessments of current potential GLOF hazards
across the IHR, and there is general consensus that the
greatest density of critically dangerous lakes occur in
Sikkim (Figure 5 and Table 1).
Ives et al.147 reported 70 potentially dangerous lakes in
the IHR. By comparison, Worni et al.148 identified 12
critical lakes in the IHR. Local assessment studies reveal
even more diverse results as an outcome of differences in
the adopted methods (Figure 5 and Table 1). These dif-
ferences across the studies highlight the need for compre-
hensive and homogeneous large-scale assessment studies
to be undertaken in the IHR. It is important to mention
that no earlier assessment studies have identified critical
lakes in Uttarakhand (Figure 5 and Table 1). Thus, the
processes relating to the Chorabari GLOF above Kedar-
nath (2013) was clearly not well captured in these pre-
vious assessments. Retrospectively, Allen et al.174
analysed the hydrological and topographic characteristics
of Chorabari lake, suggesting that such lakes fed entirely
from rainfall and snowmelt (without connectivity to gla-
cio-hydrological system), may be most susceptible to
breaching during heavy snowmelt and rainfall events159.
Furthermore, these GLOFs events may become increa-
singly more important in future, as glacial systems trans-
form into paraglacial systems dominated by fluvial
CURRENT SCIENCE, VOL. 120, NO. 5, 10 MARCH 2021 781
Table 1. Status of glacial lakes in different states and selected sub-basins in IHR
Area Number of glacial lakes Hazard assessment References
Jammu and Kashmir (Indus Basin) 1400 (>0.01 km2) 40 Lakes potentially dangerous 147, 220
103 (>0.01 km2) 2 Lakes critical 148
Uttarakhand 127 (>0.01 km2) 0 Lakes potentially dangerous 147, 221
362 8 Lakes potentially critical 159
27 (>0.01 km2) 0 Lakes critical 148
Dhauli Ganga basin (Kali Ganga) 7 2 Lakes potentially hazardous 161
Alaknanda basin 45 (>0.01 km2) 0 Lake vulnerable and susceptible to outburst 160
Himachal Pradesh 156 (>0.01 km2) 16 Lakes potentially dangerous 147, 222
65 (>0.02 km2) 23 Lakes potentially dangerous 154
45(>0.01 km2) 2 Lakes critical 148
Satluj Basin, Himachal Pradesh 40 (>0.01 km2) 3 Lakes potentially dangerous 147, 222
Chandra-Bhaga Basin 31 2 Lakes potentially dangerous 157
26 (>0.005 km2) 16 Lakes susceptible to outburst 158
Sikkim 266(>0.01 km2) 14 Lakes potentially dangerous 147, 223
50 (>0.01 km2) 8 Lakes potentially dangerous 148
472 (>0.01 km2) 16 Lakes high – medium susceptibility 164
37 (>0.1 km2) 18 Lakes potentially dangerous 163
12 Potentially dangerous 162
Figure 5. Comparison of GLOF hazard assessment results conducted
across the Indian Himalayan Region (IHR). (*)147 is based on
underlying inventories compiled for Himachal Pradesh: HP220,
Uttarakhand: UK221, Sikkim: SK222, and Indus basin of Jammu and
Kashmir – JK219. No critical, potentially dangerous or potentially critical
lakes have been identified in Arunachal Pradesh.
Given the close proximity of development activities
(including roads, dams, hydropower, and tourism infra-
structure) to glaciated mountain headwaters across the
IHR, a coordinated regional analysis of glacial lake deve-
lopment and associated GLOF risk is urgently required.
Floods and landslides
Floods and landslides are common across the IHR175, and
are characterized by extraordinary capacity for fluvial
erosion and sediment transport176. Triggering processes
include intense rainfall associated with the lift of humid
monsoon air masses along the Himalayan relief177, cloud-
burst39, and/or snowmelt processes178,179. Every year,
flood and landslide disasters cause substantial economic
losses and death in populated downstream valleys.
Extreme events disrupt infrastructure and can enhance
poverty levels within local vulnerable communities180.
Massive floods can also trigger the outbreak of epidem-
ics181,182, and stress crops or ecosystems183. Landslides
can block river corridors, creating ephemeral lakes with a
risk of dam failure causing devastating downstream
flooding184,185, and provide large amounts of sediment
which affects fluvial geomorphology176.
Recent disasters in the IHR have highlighted the vulne-
rability of the population living in the region (Figure 6),
most notably with the catastrophic June 2013 events in
Uttarakhand174, and during September 2014 and March
2015 in Jammu and Kashmir186. According to Singh and
Kumar180, more than 88,000 lives have been lost in India
since the 1950s due to floods alone, with an average eco-
nomical cost of almost US$ 460 million/yr. Main contri-
buting factors increasing the risk from extreme events
include the intensified human use of exposed mountain
catchments and downstream flood plains, poor land-use
practices such as deforestation and road construction, as
well as issues of illiteracy, gender and other social
characteristics of the population living in rural
Positive trends in flood occurrences have been reported
over India during the last few decades18 0,192. Kumar and
Santosh found positive, but not statistically significant
trends in flood peaks during the last five decades in
Himachal Pradesh. This observation agrees with the
reconstructed regional tree-ring flood records from the
north-central parts of Himachal Pradesh193, and the in-
creasing trends observed over the northwestern IHR dur-
ing the last three decades194. Long-term palaeoflood and
historical records can provide a stronger basis from which
to assess extreme events and associated trends over recent
decades. Based on such records195, it has been concluded
that the frequency of high-magnitude floods has increased
significantly during the last decades of the 20th century
across India, while Ely et al.196 reached similar conclu-
sions for the central part of India. In the Kashmir valley,
the magnitude of recent floods events (including the
devastating events of 2014) is comparable to the extreme
events that took place during the last centuries197. Multi-
centenial palaeoflood records in the central Indian Hima-
laya indicate an increase in flood frequency during the
last two centuries198, and show the key role of landslide
lake outburst floods (LLOFs). Kale et al.195,199 suggested
an analogy between the cluster of large flood events in
the recent decades and those identified during the me-
dieval warming period. Overall, while there is some con-
sistency in increasing flood occurrences over the past
decades across the IHR, underlying trends in extreme
rainfall events are heterogeneous, thus suggesting that
other factors such as land-use change likely play a role.
Hydrology, agriculture and ecosystems
The extent to which changes in climate and the high-
mountain cryosphere have and will translate into impacts
on run-off and hydrology varies significantly across dif-
ferent basins of the IHR, owing to the contrasting influ-
ences of monsoon, snow, and glacier regimes200. Whereas
earlier assessment reports of the IPCC have generalized
the role of the Himalayan cryosphere as sustaining run-
off during the summer melt season (as is valid for many
other alpine regions of the world); a more complex pic-
ture is now evident. The present-day contribution of snow
and ice meltwater is considered important to river run-off
in the Indus and Brahmaputra basin19, with overall rela-
tive annual melt contributions of up to 46% and 19%
respectively201. However, in the monsoon-dominated
Figure 6. Overview of major flood, lake outburst (GLOFs and
LLOFs) and mass movements across Jammu and Kashmir, Himachal
Pradesh and Uttarakhand. Event locations are based on a review of
published literature.
Ganges basin, the contribution is more modest at only
9%. Here, meltwater typically only supplements the peak
summer flow generated by the monsoon rainfall, although
glaciers play an important buffering role during low mon-
soon years200. Under projected future changes in climate,
a general increase in runoff is consistently demonstrated
across all basins until around the mid-21st century, owing
to changes in precipitation and/or accelerated melt19,20.
However, as glacier area decreases, late spring and sum-
mer discharges will eventually reduce considerably,
particularly for the Indus and Brahmaputra basins, with
potentially severe consequences for food security19.
One of the largest sources of uncertainty in understand-
ing past and future changes in run-off relates to the
paucity of in situ measurements of snow cover20 2. This is
crucial, because even where snowmelt contributes only
modestly to annual run-off totals, as in the case of the
Ganges, the contribution may be significant during the
spring months203. It is therefore evident that climatic
changes – in the form of increasing temperature or
decreasing winter precipitation – might have important
and as yet poorly quantified impacts on the timing or
amount of spring snowmelt, with related implications for
sustaining agriculture when other sources of run-off are
Additional to the impacts of changing cryosphere-
related run-off on agriculture, the Himalayan agro-
ecosystems have been stressed through higher mean
annual temperatures, altered precipitation patterns and
frequent extreme weather events12,21,204. However, a
variety of changes have emerged in traditional resource
utilization patterns mainly in response to population
growth and rapid urbanization in the region205,206. These
changes have sharply accentuated pressures on food and
livelihood systems through disruption of ecosystem ser-
vices and collapsing of conventional production systems,
where subsistence agriculture in the Himalayan region
often constitutes a main source of rural food and liveli-
For example, Xu et al.209 discuss that changes in cli-
mate and melting of the Himalayan glaciers are expected
to provoke cascading effects in the region, which would
affect water availability (amount seasonality), biodiver-
sity (endemic species, predator–prey relations) and
ecosystem boundary shifts (tree-line movements, high-
elevation ecosystem changes). This will also have
environmental and social impacts that likely increase
uncertainty in water supply and agricultural production
for human populations209. Some studies demonstrate that
Himalayan production systems are already declining due
to various drivers, as reported by Tiwari and Joshi210 for
the Central Himalayas and by Sharma et al.211 for the
Sikkim Himalaya. These drivers are often climate
change related, but there may be also a nexus to socio-
economic developments and/or institutional/governance
CURRENT SCIENCE, VOL. 120, NO. 5, 10 MARCH 2021 783
Synthesis of key impacts
Across the IHR, mean temperature has increased over the
past century at a rate that far exceeds the global average,
while changes in precipitation show heterogeneous pat-
terns and no clear trends at the regional scale are avail-
able. Resulting impacts on the cryosphere are seen in the
glaciers and snow cover. Warming has driven widespread
shrinkage of glaciers, and corresponding formation and
enlargement of thousands of glacier lakes. While catas-
trophic outburst events from these lakes have been rarely
documented in the IHR, several critically dangerous lakes
have been identified, and in general, the outburst poten-
tial is expected to increase as glacial lakes continue to
expand over the 21st century. Snow-cover data are rela-
tively scarce, but nevertheless, a general decline in snow
cover has been observed since the 1960s, with more vari-
able trends since 2000. Permafrost, as the subsurface
component of the cryosphere, has only recently become a
focus of systematic studies in the IHR, and as such, there
is currently insufficient evidence to link warming and
thawing of permafrost to impacts. Floods and landslides
have caused particular devastation across several Indian
Himalayan states, and are clearly linked to weather and
climate extremes. However, the observed increase in
flood and landslide events over the past few decades must
be viewed in the broader context of anthropogenic effects
such as deforestation, road-cutting, increasing exposure
of people and assets, and other poor land-use practices
that have become evident. Nevertheless, in some catch-
ments there is evidence that both heavy rainfall-triggering
events and flood frequencies have increased over the past
several decades compared to earlier period documented in
long-term palaeo archives.
In general, changes in climate, when coupled with
other socio-economic drivers of changes, are expected to
have significant impacts on lives and livelihoods across
the IHR (Supplementary Figure 5). For some catchments
or villages, this has been clearly demonstrated, with crop
failure and loss of agricultural productivity linked to
changes in hydrological regimes and impacts of extreme
weather (both floods and droughts). Likewise, for spe-
cific catastrophic events, far-reaching societal impacts
have been documented. For example, following the 2013
flooding in Uttarakhand, which has been linked to ex-
treme rainfall, snowmelt and breach of a glacier lake,
there was a 85% reduction in tourism, with an estimated
loss of US$ 1850 million to the State’s tourism sector212,213.
In fact, the impacts of lake outbursts, flash floods and
landslides on mountain communities and livelihoods, and
transport and energy infrastructure are among the most
prominent features of climate and cryosphere changes.
The energy sector faces particular challenges. Since
India’s energy consumption increased by 51% between
2000 and 2010 and is likely to continue to experience
substantial growth, further development of hydropower in
the IHR is therefore a national priority. However, but both
the existing and planned hydropower plants are exposed
to potential outburst floods from glacial lakes, often with
10 to >100 lakes upstream of single plants21 4. Some re-
cent disasters have highlighted the transboundary nature
of climate impacts in the Himalaya, with LLOFs in 2000
and 2005 originating in Tibet, causing loss of life and
substantial economic impact over 100 km downstream in
the Indian State of Himachal Pradesh185. Hence, monitoring
and exchange of knowledge needs to take place across
political boundaries, guided by international best practices.
Overall, systematic studies linking climate change in
the IHR with downstream impacts and risks are lacking,
and studies have been seriously hampered by limitations
in monitoring, data availability and knowledge exchange.
The sparsity and paucity of hydro-meteorological obser-
vations over the IHR are crucial limitations, with most
stations located in the valley bottoms, hence unrepresen-
tative of the high alpine areas26,215. In addition, the coarse
representation of high-altitude topography/mountains in
climate models limits understanding of present as well as
the future climate, and RCMs are still not capable of
resolving precipitation distribution over the IHR due to
high uncertainties with increased greenhouse concentra-
tion216,217. Heterogeneity in results relating to precipitation
changes may be attributed to the dataset, methodology,
parameterization scheme used in data reconstruction and
model simulation, and the domain of study chosen for the
analysis. In addition, various model results have defined
uncertainties embedded within them, and hence these re-
sults need to be used with utmost care for hydrological
and glaciological studies. Improvement in model parame-
terization and increased observational data will thus play
an important role in better understanding of rainfall dis-
tribution over the IHR and related impacts at present as
well in future.
In case of glacier and snow cover studies, in situ data
need to be strengthened as the basis for improved model-
ling202 and further ice-core studies are needed to ascertain
past snow-ice evolution. Further, regional estimates on
variation of the derived snow parameters (such as snow-
line altitude, snow depth and snow-water equivalent)
need to be made available for the wider research commu-
nity, and regional variations in glacier response need to
be addressed in detail focusing on causative factors,
including regional climate feedbacks relating to black
carbon. The World Meteorological Organization lists
permafrost as an essential climate variable and some
encouraging firm steps have been taken by the national,
regional and international agencies to promote permafrost
research in the IHR142.
Conclusion and recommendations
Future warming over the IHR is projected to exceed
2.5°C by the end of 21st century, based on 129-yr period
(1971–2099) analysis, even under low greenhouse gas
emission scenarios, and consistent increases in monsoon
precipitation are expected. Furthermore, studies point out
an increase in the occurrence of extreme phenomena such
as floods, which when combined with increased human
pressure on the natural environment and land-use degra-
dation in the region, have in some instances led to cata-
strophic consequences.
Limitations in spatial and temporal data coverage, and
heterogeneous research methodologies have been identi-
fied as key factors leading to uncertainty in observed and
projected impacts of climate change in the IHR. In this
regard, we recommend improved coordination of research
activities across institutional divides, facilitated at the
national level through programmes that support and
enhance cooperation. India is a world leader in remote
sensing technology, and India Meteorological Department
has invested significantly in improved monitoring of rain-
fall over mountain regions. Yet, there are often difficul-
ties for researchers to access such data.
Diversity in research approaches and methodologies,
and the critical debate over it, are important, but as seen
in the example of GLOFs, different methodologies can
lead to vastly different implications for assessed levels of
hazard and risk which eventually and occasionally can re-
sult in confusion at the level of decision-making. Hence,
we call for regular and coordinated reassessment of such
threats, to use latest best practices, and furthermore, to
account for the fact that environmental and societal base-
line conditions are rapidly changing. International colla-
boration is also seen as important factor for strengthening
institutional and scientific capacities in the IHR. For ex-
ample, mountainous countries such as Switzerland have a
long history of responding to the challenges of climate
change, therefore experiences may be shared with Indian
counterparts on both academic and political levels. Indian
science has a broader role to play here, as a leading
knowledge partner in the wider Himalayan region. This is
particularly important, given that many potential down-
stream impacts are far-reaching and transboundary in
nature. Meanwhile, at the local level, there are opportuni-
ties to engage communities directly in the knowledge-
generation process to better understand observed changes,
timing and magnitude of impacts at the ground level.
Such ‘citizen science’ activities are growing internation-
ally, for example, with landslide-mapping initiatives
based on smartphone apps. Finally, we highlight the im-
portance of interdisciplinary approaches that are required
to truly understand and address complex upland – low-
land linkages driven by climate change and additional
socio-economic stressors. This applies for all sectors, but
undoubtedly becomes most pronounced when considering
climate change impacts on rural livelihoods. We recom-
mend bottom-up approaches, starting with a comprehen-
sive framing of social dimensions and identifying
potential risks through stakeholder discussions, before
progressing to physical modelling and assessment of how
such risks will be influenced by climate and related bio-
physical impacts218.
Considering wide-ranging ways in which societies inte-
ract with and depend upon mountain environments, im-
proved systematic and coordinated monitoring across the
IHR, feeding into comprehensive and interdisciplinary
assessment approaches, will be essential to ensure that
local adaptation decisions are evidence-based, take
diverse sources of knowledge into account and are well
supported by latest scientific understanding.
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ACKNOWLEDGEMENTS. This study has benefitted from collabora-
tions promoted by the Indian Himalayas Climate Adaptation Pro-
gramme (, a project under the Global Programme
Climate Change and Environment of the Swiss Agency for Develop-
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Studies, Ministry of Environment, Forest and Climate Change, GoI.
doi: 10.18520/cs/v120/i5/774-790
... The Cryosphere changes are first experienced at the local level where the indigenous communities are closely interwoven with the natural resources, climatic variations and local cultural belief (Beniston, 2003;Joshi et al., 2015). Cryosphere changes and its consequences, as reported by the people living in this fragile ecosystem, include irregularities in rainfall, shortening of the winter season, increase in temperature, reduction in snow-cover and snowfall, and changes in the distribution of the indigenous species of flora and fauna in the region (Negi, 2012;Paudel & Andersen 2013;Ranjan et al. 2020 in climatic parameters like temperature, snowfall, rainfall and surface runoff in more recent times however are felt by the inhabitant which has a direct and immediate effects on their livelihoods (Mc Dowell et al., 2019;Dimri et al., 2021). ...
... One of the threats has been shortage of water; the other refers to enhanced frequency and intensity of natural hazards-both adversely affecting the life and livelihood of the inhabitants. People living in the fragile mountainous region are highly vulnerable to even minor changes in environmental conditions (Messerli & Ives, 1997 irregularities in the frequency and intensity of rainfall and snowfall (Dimri et al., 2021). The peak rainy season commence around June and has now shifted to the third week of July (Joshi et al., 2015). ...
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This paper is a perception-based study that aims at understanding the impact of climatic variability on livelihood opportunities in the Cryosphere highland of the mid-Himalayan region. The region faces environmental challenges affecting livelihood linkages linked to agriculture. Data analysis involves descriptive statistics, bivariate analysis (chi-square and likelihood ratio) and logistic regression to understand issues and association. There is a significant association between climatic variables and livelihood options. The logistic regression model shows that there is an integrated impact of climatic factors such as precipitation and temperature etc. on snowline change. A similar integration was also found on altitudinal change in vegetation. Local people's perception reflects changing livelihood options with the changes in climate.
... The westerly disturbance and monsoon circulation are two main climate system affecting precipitation anomaly in the Indian subcontinent (Dimri et al., 2021;Priya et al., 2016). The upper-level divergence is favorable for low-level convergence which results in severe weather patterns. ...
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Floods are considered as one of nature's most destructive fluvio-hydrological extremes because of the massive damage to agricultural land, roads and buildings and human fatalities. Rapid development of unplanned infrastructural conveniences and unplanned anthropogenic activities, the frequency and intensity of floods have been accelerated in the recent years. Therefore, flood susceptibility analysis is considered as an important flood management approach. Identification of flood susceptibility areas has been performed applying advanced machine learning (ML) algorithms (random forest (RF), support vector machine (SVM) and extreme gradient boosting (XGBoost)) at the lower part of Raidak river basin. The flood susceptibility maps have been generated based on 14 different flood conditioning factors. Models are evaluated in a conventional way using ROC (receiver operating characteristics) curve. The AUC value of ROC is above 0.80 for all models and XGBoost depicts highest efficacy (AUC = 0.92). Friedman test and Wilcoxon Signed rank test have been used to measure the statistical variances among the applied models. Models proficiently show that the upper part of Raidak river basin is less flood probable region whereas the eastern and some middle parts have high flood probability. Around 27% areas (285.39 within the river basin is highly flood prone (based on XGBoost model) due to fast changing dynamic landscape and large scale human intervention. The important outcomes of this research will definitely assist the local administrators to take proper sustainable management plan for the reduction of future damages.
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Despite recent research identifying a clear anthropogenic impact on glacier recession, the effect of recent climate change on glacier-related hazards is at present unclear. Here we present the first global spatio-temporal assessment of glacial lake outburst floods (GLOFs) focusing explicitly on lake drainage following moraine dam failure. These floods occur as mountain glaciers recede and downwaste. GLOFs can have an enormous impact on downstream communities and infrastructure. Our assessment of GLOFs associated with the rapid drainage of moraine-dammed lakes provides insights into the historical trends of GLOFs and their distributions under current and future global climate change. We observe a clear global increase in GLOF frequency and their regularity around 1930, which likely represents a lagged response to post-Little Ice Age warming. Notably, we also show that GLOF frequency and regularity – rather unexpectedly – have declined in recent decades even during a time of rapid glacier recession. Although previous studies have suggested that GLOFs will increase in response to climate warming and glacier recession, our global results demonstrate that this has not yet clearly happened. From an assessment of the timing of climate forcing, lag times in glacier recession, lake formation and moraine-dam failure, we predict increased GLOF frequencies during the next decades and into the 22nd century.
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The high-resolution climate model Providing REgional Climates for Impacts Studies (PRECIS) was used to project the changes in future extreme precipitation and temperature over the Koshi River Basin for use in impact assessments. Three outputs of the Quantifying Uncertainties in Model Prediction (QUMP) simulations using the Hadley Centre Couple Model (HadCM3) based on the IPCC SRES A1B emission scenario were used to project the future climate. The projections were analysed for three time slices, 2011-2040 (near future), 2041-2070 (mid-century), and 2071-2098 (distant future). The results show an increase in the future frequency and intensity of climate extremes events such as dry days, consecutive dry days, and very wet days (95th percentile), with greater increases over the southern plains than in the mountainous area to the north. A significant decrease in moderate rainfall days (75th percentile) is projected over the middle (high) mountain and trans-Himalaya areas. Increases are projected in both the extreme maximum and extreme minimum temperature, with a slightly higher rate in minimum temperature. The number of warm days is projected to increase throughout the basin, with more rapid rates in the trans-Himalayan and middle mountain areas than in the plains. Warm nights are also projected to increase, especially in the southern plains. A decrease is projected in cold days and cold nights indicating overall warming throughout the basin. © 2017 National Climate Center (China Meteorological Administration).
In September 2014, the Kashmir valley (north-west India) experienced a massive flood causing significant economic losses and fatalities. This disaster underlined the high vulnerability of the local population and raised questions regarding the resilience of Kashmiris to future floods. Although the magnitude of the 2014 flood has been considered unprecedented within the context of existing measurements, we argue that the short flow series may lead to spurious misinterpretation of the probability of such extreme events. Here we use a millennium-long record of past floods in Kashmir based on historical and tree-ring records to assess the probability of 2014-like flood events in the region. Our flood chronology (635 CE–nowadays) provides key insights into the recurrence of flood disasters and propels understanding of flood variability in this region over the last millennium, showing enhanced activity during the Little Ice Age. We find that high-impact floods have frequently disrupted the Kashmir valley in the past. Thus, the inclusion of historical records reveals large flood hazard levels in the region. The newly gained information also underlines the critical need to take immediate action in the region, so as to reduce the exposure of local populations and to increase their resilience, despite existing constraints in watershed management related to the Indus Water Treaty.
Mountains are fragile ecosystems with global importance, providing key ecosystems services within mountainous areas but also for the lowlands. However, mountain regions are prone to natural disasters and exposed to multiple hazards. In this chapter, we present four disaster databases (EM-DAT, NatCatSERVICE, DesInventar, Dartmouth) that store information about spatiotemporal occurrence and impacts of natural disasters in mountain areas. Quality and completeness of the four databases are compared and analyzed regarding reliability for weather- and climate-related natural disasters. The analysis identifies the numbers of fatalities as the most reliable loss parameters, whereby the number of people affected and the economic loss are less trustworthy and highly dependent on the purposes of each database. Main limitations regarding sustainable mountain development are the inhomogeneity in database definitions, spatial resolutions, database purposes and lack of data registration for human and economic losses. While some individual disasters such as the Kedarnath flood in northern India in 2013 have been robustly linked to changes in climate, there is generally insufficient evidence to attribute any overall increasing disaster frequency to climate change. Damage due to hazard in mountain regions will increase irrespective of global warming, in regions where populations are growing and infrastructure is developed at exposed locations.