The dark soot particles that are thought to accelerate the melting of Himalayan and Tibetan glaciers are found to come largely from fossil fuel combustion in the North Indian sub-continent and China, according to a study in Nature Communications this week. Identifying the source of these particles could provide improved guidance for effective pollution-mitigating action.

Many of the glaciers within the Himalayas and Tibetan Plateau are beginning to thin, causing grave concern for the billions of people who depend upon the seasonal melt water. Model simulations suggest that this thinning is mainly due to the presence of black carbon aerosols, or soot, the heat radiating properties of which warm the air and ice surface.

Shichang Kang and colleagues use a dual-carbon-isotope fingerprinting technique to identify the chemical signature of black carbon particles recovered from the atmosphere and snow surface across the Himalayas and Tibetan Plateau. The technique enables the authors to distinguish between source type (biomass or fossil fuels) and source region. The signature of the samples recovered from the northern Tibetan Plateau indicates that the black carbon is predominantly from Chinese fossil fuel sources (accounting for around 66% of the samples). By contrast, black carbon particles sampled from the Himalayas were equally composed of biomass and of fossil fuel sources from the Indo-Gangetic Plain, a region in the North Indian sub-continent.