Surabi Menon, a scientist with Lawrence Berkeley National Laboratory in California, and colleagues looked at two sets of inventories of black carbon aerosols by Indian researchers. Their simulations – the results of which were published in Atmospheric Chemistry and Physics – showed that about 90 per cent of the change in snow and ice cover can be attributed to aerosols, and black carbon contributes at least 30 per cent of this.

Black carbon is the result of the incomplete combustion of fossil fuels and biomass, and is especially prevalent in India as a result of its rapid industrialisation – emissions of Indian black carbon increased by 51 per cent during 2000–2010. Unlike other atmospheric aerosols, black carbon absorbs sunlight; and unlike greenhouse gases, it only warms the atmosphere, resulting in a potent effect on atmospheric temperatures. And when deposited on a glacier, it absorbs more sunlight than pure snow and ice, producing an albedo effect that accelerates melting.

‘Our simulations showed greenhouse gases alone aren’t nearly enough to be responsible for the snow melt,’ Menon said. She added that the contribution of black carbon could be even higher than 30 per cent – other Indian observatories’ measurements were higher than the inventory’s, but were too incomplete to be used in climate models.

April 2010