Impacts of Climate Change on
Water Towers of Asia

 

 

M

elting glaciers, unpredictable weather conditions, increasing
temperature and changing rainfall patterns are all the proves that impacts of
climate change in the Himalaya are real. These impacts not only poses threat to
climate and humans but significantly also to wildlife.

One of the most sensitive global hotspot of climate change
today is Himalaya with impacts manifesting on a very rapid pace. In coming
years, this situation is predicted to intensify adversely impacting food, water
security with biodiversity and species loss. This effect will not just be in
Himalaya, but throughout Asia.

More than a billion people depend directly on the Himalaya
and its habitats survival, 450 million in China, 500 million more in South Asia
and 200 million in Pakistan. These glaciers are the water towers of Asia. They
are the biggest source of world’s great rivers: The Indus, the Gangee, the
Yangtze and the Mekong. Everyone survival is on the survival of this fragile
mountain landscape.

The Intergovernmental Panel on Climate Change in 2014 adopted
four Greenhouse gas concentration trajectories in its Fifth Assessment Report AR5.
These pathways leads us to research and climate modelling. The tracks of these
pathways explains four possible climate future which allow us to study the
emission of greenhouse gases in the years to come. The Representative
Concentration Pathway (RCP) gives us the range of the Radiative forcing values
in the year 2100 comparable to pre-industrial values.  The RCP 2.6, RCP 4.5, RCP 6, and RCP 8.5 are
the values of radiative forcing.

The diagram shows the net negative global emissions from
fossil fuel and other sources of environmental pollutants. It is clearly shown
according to RCP directions that by the year 2100 the emissions will rise up to
dangerously destructive level keep the current rate of emissions.

 

Figure (1). The diagram
shows the emission of Greenhouse gases emissions till the end of the century.

 

 

I

n the gigantic
mountains of Asia lies the World highest mountain ranges. Those vast area of
snow covered ranges make a notable contribution to the supply of fresh water to
millions of people from South West to North East of the whole continent. The
anthropogenic climate changes are making the glaciers to lose the mass and
they’re retreating them as a result. The meltwater river systems on planet are
highly dependent on these mountain ranges originating from them.

The variations
in Snowfall and Temperature is the prime physical example to witness the
climate change. Whenever the change occurs, the difference of both happens
first. The leading cause of this phenomena is surface heat loss, water vapour
changes, the latent heat release, radiative flux changes, surface-based
feedback, and the effects of snow albedo and aerosols which can be seen in the
study of HMA Mountains.

The
temperature of glacier areas of Himalaya mountain area is constantly rising at
much higher rates compared to other land masses. The difference between the
global average temperature and the temperature rise of HMA is because of the
radiative forces which are acting faster compare to other areas, thus it is
less evident but still pronounced. The mean temperature increase of all the RCP
shows a constant rise in the temperature through the coming century. It has
clearly shown that the East of Himalaya and Karakoram are the most affected
area of this change.

                                Figure
(2). The diagram shows the four RCP values with the rise in temperature.

 

How the increase in Global Temperature
especially in the Himalaya Mountain Areas (HMA) affecting the whole Range of the
mountain?

The changes in
the past years were not taken seriously into account but the studies on the
region shows a very fast growing trend of glacier melting and the debris
reduction. A debris has a very propitious effect on the glaciers. It holds a very
firm control on glacier ablation which aid the climate sensitivity. A thick
layer of debris acts as an insulator for underlying ice which suppresses the
ice from melting whereas thin layer of debris has lower albedo than debris-free
ice which accelerates melting.

Figure (3). The diagram
shows the relation between the Thickness of Debris to the Relative Ablation.

 

The Debris on
ice plays a vital role to regulate the melting process of the glaciers. The
layer of Debris acts as an insulation sheet which lower the melts rate and
gradually shows down the mass loss and the retreat of glaciers. The important
consideration to take here is How much the total area this debris covers? The
debris level compare to the total amount of glacier is very less. The regions
like Karakoram and Himalaya has 40% of there glaciers beneath this debris which
protects them as it exceed the ablation zone by 40% which results in strong
buffering effect. Over the course of coming century, the effect on debris
thinning will increase the overall effect of climate change.

 

Figure (4). The above diagram shows the projections of mass
loss of different regions of HMA for the different RCP scenarios. The different
models also shows a rise of temperature at the end of the century. The relative
presence of debris has been shown in different bar charts It is clearly evident
from diagram that by the time of RCP 8.5, the remaining mass of the most of the
glaciers will be lost.          

 

Glacier mass
balance decides the health of a glacier. If the total quantity of frozen
precipitation in the accumulation zone is greater than the quantity of ice of
glacier lost because of melting or in the ablation zone, the glacier will move
forward, if the accumulation is less than ablation, the glacier will retreat.
Because of it, glacier will have negative mass balance which will retreat it
and if they don’ find the balance between accumulation and ablation, the
glacier will eventually disappear. The diagram explains the relation between
the remaining area of the glaciers and the different RCP scenarios. It explains
that with the current level of emissions of gases and the keeping in view the
current situation most of the glaciers will lost a huge sum of ice level by the
end of the century.

Figure (5) Remaining area of the
glaciers by the end of century. All the sub-regions (a-o) shows the bar plots
with the glacier area that will be left by the end of the century (2071-2100).

 

With the
effect of Debris on the underneath glaciers the water streaming will going to
increase to alarming situation. The poor understanding of the hydrological
regimes of high rivers is the main cause of uncertainty in accessing the
hydrological impacts of regional climate changes in those areas.

How the Asian Monsoons are affecting?

The climate of
Himalaya determines the monsoon system of Indian and South-Asian monsoon rains.
It cause the large scale precipitation to occur during the month of
June-September. It causes orographic effects which shows a strong north-south
gradient by the precipitation intensity. The patterns of precipitation in
Karakoram and Hindu-Kush ranges are mostly characterized by the south-Westerly
and Westerly flows which causes the precipitation to fall more equally. The
Karakoram high-altitude precipitation which is almost two-thirds usually happens
in the winter months. 

The two types
of precipitation, solid and liquid is formed because of the basin hypsometry
which regulates the ratio of solid and liquid precipitation within a basin. The
perennial snow or ice is stored in long term which is a solid precipitation and
acts as seasonal snow before it melts and runoff. On the other hand, the liquid
precipitation directly run off. The groundwater actually determines the run off
delay which usually happens by infiltration into the soil. The climate variability
and change is largely determined by the magnitude of these runoff components
and how much they are contributing to. The total runoff components controls a
basin’s run off composition by determining the contribution of each solid and
liquid precipitation. 

The
high-resolution cryospheric-hydrological model examines the upstream runoff
composition in the largest rivers basins of Asia.

The charts of
Bar plots in Figure () explains the annual average runoff generation for
different periods. The maximum runoff stream flow is in Upper Indus Basin (UIB)
which contributes 40.6% of melt water. In the Upper Gangas Basin (UGB), most of
the runoff is rain dominated and contributes only 11.5%, despite of its large
glacier area. The Upper Brahmaputra Basin (UBB) shares the equal amount of run
off as (UGB) does but it has slightly more snow melt compare to UGB. It is
because of the hypsometry of the basins which favours solid precipitation in
this basin.

 

 

    

Figure (6) The diagram shows the different basin and their average
run off generation of different basins.

 

 The runoff composition and total runoff volume
will change by 2050. The model outputs the different runoff values generated
from each component of snowmelt, glacier melt, baseflow, and total runoff.

Figure (7). The diagram show the different factors
contributing towards the melting down of runoff factors.

 

 The following table shows the change in
Temperature and Precipitation by the end of the century. It clearly shows that
with such runoff factors and melting of ice and river will lead to 8.2 C
increase in Temperature and 11.0 in precipitation.

 

So what does this change in temperature and precipitation has
caused?

In the Southeast Asia, the most
important factor which influence the regions climate is Monsoon rains. It is
the most heavily dependent weather system which totally rely on the climate
response of the Himalaya Mountains behaviour. During the past years, the
monsoons have caused a lot of damage and destruction to environment and
farmlands, causing extensive financial loss and other damages. This causes a
main issue of food insecurity as well.

It is really important to understand the
outcomes of these change. All the factor explained before are the driving cause
of unpredictable monsoon which is increasing every year. The highly occurred
cause of these is the Global increase in temperature which has also affected
the Himalaya mountain ranges as well. The diagram explains the increase in the
air temperature of the HMA from past century which now results in more rains.

 

 

Figure(9). Increase in air temperature w.r.t time

The diagram explains the increase in the
air temperature of the HMA causing the more precipitation from past century
which now results in more rains. It clearly shows the increase of 0.104 C per
decade each and still rising.

This phenomenon has caused the
precipitation of increase on alarming level. Because of this precipitation now,
there are three times more monsoon, before season and at unprecedented time.
This is causing the more ice to melt and over flooding the streams of water
that are ultimately making the river level high from normal.  

 

Figure (10) The diagram shows the results of precipitation
level. The red areas are the most with the hot climate which is actually
causing a lot of these rainfalls.

 

Conclusions

To conclude, the most important point
above everything here is that the 1.5? C increase in temperature is real. Yes it is.

The increasing
rains, floods, and out of season weather changes are all the impacts of climate
change.