Monday, 18 November 2013

Climate Change in the Himalayas

This is an assignment which I've submitted as a part of an online course "Global Warming: The Science of Climate Change" offered by the University of Chicago.
I have focused my assignment on interpreting the data from meteorological stations located within the Himalayas and the Tibetan Plateau.

This region is significant as 1.3 billion people i.e 20% of the world's population is dependent either directly or indirectly on the Himalayan glaciers. The Himalayas supply freshwater to 8 South-Asian countries, including two of the most populous countries in the world i.e China and India. Any catastrophic change in the Himalayan climate is sure to effect the culture and demography of the area and the political scenario of the world.

Apart from Kangding (China) which showed a decrease of 0.03 degrees Celsius in average temperatures and Darjeeling (India) where the temperature remained practically unchanged from 1900 to 2013, all of the 38 stations showed an average increase of 0.6 degrees Celsius in the average annual temperature.

Breaking this range down, in the period from 1900-1950,1950-1975, 1975-2000 and 2000-2013 the average temperature saw a rise of 0.1, 0.12, 0.135 and 0.23 degrees Celsius respectively in the corresponding ranges. Notice something? The average temperature has not only been increasing, but it has been increasing at a faster rate! The Temperature Trend (°C / Decade) from 1850 to 2013 is 0.03, from 1900 to 2013 is 0.11 and from 1970 to 2013 is 0.29!

The map below shows the extent of the Himalayan snow cover from 1900 to 2013. The decrease in snow cover is obvious.
Another graph which I'ld like to highlight is the length of the Gangotri glacier. This glacier is the source of the Ganges river and from the graph, we can see that it has receded by almost 1.4 kms from its recorded length in 1900! Once this glacier melts off, more than 400 million people shall be affected adversely either directly or indirectly.

Apart from usual factors like increasing CO2 levels and decreasing forest cover, another factor which has recently come into limelight for the decreasing Himalayan snow cover is soot. Soot is made of black carbon particles produced by inefficient burning of wood, a major source of energy in rural South-East Asia. Not only does soot linger around in the atmosphere and absorb sunlight to increase the atmospheric temperature, but it also falls on the glaciers (since the air becomes cooler over the Himalayas and descends), and decreases their albedo. The glaciers absorb more sunlight and this hastens their retreat. This is a reason why the increase in temperature of the Himalayas is more than 5 times the global average!

Quoting from the Scientific American:
"Using data from an international atmospheric observatory in Nepal,Teppei Yasunari of the NASA Goddard Space Flight Center in Greenbelt, Md., and his colleagues estimated the amount of soot that falls on a typical Himalayan glacier. The team’s computer simulations suggested that the soot can cause a decrease of between 1.6 and 4.1 percent in the glacier's albedo—a measure of its sunlight-reflecting "whiteness"—and that the resulting heating can cause up to a 24 percent increase in the annual snowmelt, Yasunari reported here Monday at a meeting of the American Geophysical Union (AGU)."

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