The News
- According to a study, black carbon travelling from Mediterranean countries during the western disturbance may be one of the important factors leading to the receding snowline in the Himalayas.
Key Highlights
- The data was recorded at Gangotri Glacier Valley in Chirbasa between January and December 2016.
- It was found that the black carbon concentration was high even in winter months, January and February, having no human activity like burning of fossil fuels or influx of tourists.
- Thus, it was concluded that black carbon aerosols were being transported during western disturbances and wind trajectories.
- Further, the concentration of black carbon during the months of January and February was fourth and fifth highest respectively among the 12 months recorded.
Background
- The Hindu Kush-Himalayan-Tibetan region is considered as the “Third Pole” of the world.
- 14 mountain ranges run in parallel from east to west, including the Altay, Tien Shan, Pamirs, Kunlun Shan, Karakoram, and Himalaya.
- Global warming is having dramatic effects on the climate system in this region.
- As a result, the majority of the glaciers in the region are retreating, and the monsoon rains are becoming less predictable.
- It has been found in earlier studies that one of the leading causes of Climate Change at the third pole is Black Carbon.
Movement of pollutants to the region
- The Tibetan Plateau is at the crossroads of influence between maritime air masses from the Indian Oceans (monsoons) and continental air masses from central Asia (westerlies).
- During the winter and pre-monsoon season (October to April), large-scale circulation patterns (predominantly westerlies) transport air masses to the Plateau.
- It was till now thought that Westerlies do not bring large quantities of pollutants with them.
- However in summer (June to September), low pressure over the plateau induces a supply of moist, warm air from the Indian Oceans to the continent (summer monsoon).
- These masses bring considerable pollution from South Asia.
- The current study has shown that the pollutants in the atmosphere get transported during the western disturbance also.
Black Carbon
- Black carbon, a component of soot, is a by-product of incomplete combustion.
- Unlike other aerosols, black carbon absorbs solar radiation.
- It mixes with other aerosols like sulfates, nitrates, and carbon to form called as Atmospheric Brown Clouds.
- The Atmospheric Brown Clouds leads to both warming of the lower atmosphere and surface dimming (due to the presence of sulfates).
- Besides increasing amounts of soot in atmospheric brown clouds have accelerated snowmelt.
Effect of Black Carbon on snow
- Snow is the most reflective natural surface on earth, with an albedo of almost 90%. Snow albedo can be reduced by very small amounts of impurities, like dust or black carbon.
- Black Carbon is estimated to be fifty times more efficient than dust in reducing snow albedo.
- One part-per-billion of black carbon (BC) on the surface can reduce snow albedo by 1-2%.
