In what could revive controversy over the state of glaciers in the Himalayas, researchers associated with the Indian Space Research Organisation (Isro) and the government-run Wadia Institute of Himalayan Geology suggest that aerosols such as soot—tiny particles that are often the result of insufficiently burnt gases—may be playing a key role in affecting glacier health.

Although previous studies, too, have suggested such a link, they relied entirely on satellite imagery. The latest study, part of a department of science and technology-funded project, is based on actual physical measurements of glaciers and, according to experts, considered an accurate picture of the contraction and expansion of glaciers.

The finding suggests that the link between contracting glaciers and climate change is far more complex than has been assumed, although the experts who conducted the study emphasize that the finding is “preliminary and more observations are required" to confirm it.

Changing conditions: The Dokriani glacier in the Himalayas.

In the latest issue of the peer-reviewed journal Current Science, the researchers say that varying aerosol concentrations in and around the Himalayan region were significantly associated with the expansion and concentration of the Dokriani glacier.

“We’ve observed this in the Dokriani, which is among the best studied and measured Himalayan glaciers and, therefore, the trend is far more reliable. However, it does seem that aerosols have an important role," said Sanat Kumar Das of the Physical Research Laboratory, Ahmedabad, an Isro organisation, and among the key authors of the study.

“It could also be that aerosols and GHGs are combining to trigger glacial melt. Also, we need more data to study such effects on bigger glaciers such as the Gangotri glacier," he added.

Although GHGs and aerosols both affect the climate, their mode of action differs. GHGs almost universally heat up the atmosphere and accelerate global warming, whereas aerosols—also a product of vehicle exhaust and stray dust particles—sometimes heat up and sometime cool the atmosphere. All international negotiations and existing treaties focus on GHGs, and aerosols—being less understood—have been out of their ambit.

The IPCC reported in 2007 that global warming was rapidly melting Himalayan glaciers and at the current rate these would disappear by 2035, a conclusion that triggered a public war of words between IPCC chief R.K. Pachauri and India’s environment minister Jairam Ramesh.

In November 2009, the environment ministry publicized a report by a former deputy director general of the Geological Survey of India, V.K. Raina, that disputed IPCC’s report.

Raina’s report said: “It would be premature to state that these glaciers were retreating abnormally because of global warming..."

In January, IPCC’s glacier claim was found to be faulty and based not on science but on a typo, and also used out of context, as reported by Mint on 20 January. IPCC subsequently retracted its claim on glaciers.