Hindu Kush Himalayan glaciers. Photo: Flickr

Tibet's Himalayan glaciers could melt because of soot from India. More destructive than global warming, soot deposits found in one glacier were attracting enough heat from the sun to power a LED bulb.

A joint study by researchers in China and the United States that was published in the latest issue of Atmospheric Chemistry and Physics found that most of the carbon-containing aerosols in the Himalayan region come from the soot generated when coal and biomass is burnt in South Asia.

Scientists based their findings on a core of ice measuring 100 metres in length that Chinese scientists retrieved during an expedition to the Zuoqiupu glacier in southeastern Tibet’s Kangri Karpo mountain range in 2007, and took to Lhasa for further study.

Bored from an altitude of 5,600 metres above sea level, the ice showed a history of soot deposits dating from 1956 to 2005.

The team described the soot as a “serial killer” in terms of how it affects the slowly moving rivers of ice that coat mountains.

When airborne, soot increases atmospheric temperatures and reduces snowfall. After it lands on ice or snow, it absorbs heat from the sun, causing glaciers to melt faster.

The fast retreat of glaciers in Tibet had long-puzzled scientists, since they have been melting at twice the estimated rate of the impact of climate change.

Their rapid erosion has greatly troubled China as its three biggest rivers – the Yangtze, Yellow River, and Lancang River in southern Yunnan province – all originate from the Tibetan Plateau. As such, the glaciers play a critical role in China’s long-term water supply.

Soot was a major suspect as previous studies found traces of black and organic carbon all over the Himalayan region, but scientists were unable to determine whether it came from China or India as both countries consume vast amounts of coal and rank as major emitters of pollutants.

Factories and farms in India are geographically closer to the glaciers, but doubts remained as to whether their emissions would be able to scale Mount Everest and find their way into Tibet.

However, “The emissions from China and India carry their own district chemical compositions,” said Prof Xu Baiqing, one of the authors of the paper. Xu works for the Chinese Academy of Sciences’ Institute of Tibetan Plateau Research in Beijing.

“For instance, the soot from China contained more black carbon from fossil fuels, while the Indian soot had more organic carbon, which resulted from the burning of hay and wood in rural areas,” he said.

Based on this, the findings indicate that India contributed 74 per cent of the black carbon and 81 per cent of the organic carbon in the core of ice, according to their analysis.

To verify whether the soot was coming from India, the researchers also used a new modelling technique developed by scientists at the Pacific Northwest National Laboratory in the United States.

The model was able to track emissions from different regions and regenerate the flow of soot in the atmosphere as it was tossed about by monsoons and other climatic events.

They found that soot levels in the Zuoqiupu glacier rose and fell over the years in proportion to the amount of coal consumed in India. They also spiked and dipped in line with the country’s hay-burning seasons.

Researchers warn that the authorities must urgently address the threat of melting glaciers – as past examples indicate – since people living along the Himalayan plateau depend on mountain water.