Every few years, the spectre of an Asian 'brown cloud', or its most recent avatar 'smog', resurfaces, and a considerable amount of public attention is paid by the world media to atmospheric conditions over the Asian continent. The first such instance was a study conducted by the UN Environment Programme (UNEP) just prior to the World Summit on Sustainable Development in Johannesburg in 2002. The UNEP chief at the time, Klaus Toepfer agreed that more research was needed for conclusive knowledge of the brown cloud; nonetheless the study specifically referred to the widespread use of cow dung and other bio-fuels.

The Indo-Gangetic plain being home to the largest concentration of people engaging in such uses - which burn fuel very dirtily - Indian scientists have always been touched to the quick by any suggestion that the fault lies, even partially, with India. And the government too has been similarly sceptical. The suspicion, then and now, is that this is motivated to distract world attention from the failure by the US and other industrial countries to cut down on their emissions of greenhouse gases. In a sharp reaction to the UNEP report, India's Environment Ministry stated that the report's conclusions were "unfounded and there is no scientific evidence to suggest any linkage between the haze and its impact on weather patterns, floods and droughts, precipitation, crop yields, acid rains, and pollution related mortality."

The ministry said that the alarming picture of the brown haze painted by the UNEP report was based on preliminary, limited modelling studies founded on several assumptions and studies from which no definite conclusions could be drawn. The haze was not specific to the Asian region but is also seen over Europe, North America, and east Asia, the Indian ministry stressed. Further, officials argued that the report's drastic conclusions about disruption of weather patterns or massive monsoons, floods, and draughts caused by the cloud were "unfounded" as the report dealt only with the winter season over South Asia, and declared that "the results of the report and the experiments cannot be applied to other seasons."

Three years ago, smog-talk resurfaced, this time under the somewhat more politically correct label of the Atmospheric Brown Cloud, doubtless to deflect attention from its location. At the Delhi Summit on Sustainable Development, Nobel Laureate Paul Crutzen and V Ramanathan of the Scripps Institute of Oceanography in the US, announced that they and colleagues were conducting a 10 million euros study on the haze which originated over Asia and spread thousands of kilometres over the earth.

Notwithstanding each nation's views, it is important to bring science to bear upon questions of national and global import. One option may be for research into smog to be carried out by an impartial body - like the UN Inter-governmental Panel on Climate Change.

 •  Clearing the air in our cities
 •  As the world heats

Commendably, the two told the summit that they wanted to bury the controversy of the past and focus on the science instead. Ramanathan told the summit that the haze was by no means only over Asia but scattered throughout the world. However, it was concentrated over South Asia because of the long, hot summers in this part of the world, which generated a lot of heat and dust. The haze is described as a mix of ash, acids, aerosols and other particles - the most dangerous being black carbon, which comes from diesel, dirty coal and biomass burning. It cuts off sunlight, which can have disastrous consequences. It is said to hover three kilometres above the surface of the earth and can cross half the globe in less than a week. Some 16 sites from the Indian Ocean to the Pacific are being set up to study its spread, origin and effects. The first super-observatory is already coming up in the Maldives as part of a UNEP initiative. In India, possible sites could be the Andamans and perhaps a place like Darjeeling. Nepal's Himalayan slopes may host sites to study if pollution deposits on snow could be hastening melting.

The latest salvo has been fired by Renyi Zhang, an atmospheric scientist from Texas A&M university, who has found that smog and air pollution from Asian cities have intensified storms over the Pacific Ocean, which will accentuate the warming of the Arctic. The polar ice caps, as is already well known, are in a state of siege due to global warming and are melting at an alarming rate. According to Zhang, the problem is compounded by the fact that in the last two decades, cities in China and India - for example, Shanghai and Mumbai, to cite twins which are or were often seen as exemplars of growth - have been burning more coal as they prosper. These particles find their way into the atmosphere and cause long-range and long-term damage.

There is no question that pollutants travel the globe with alarming ease. Glaciological analysis of the polar ice caps reveals that dust from mines operated in the time of the Roman empire found their way to the high latitudes. The ease with which pollutants are transported in the atmosphere is one reason why even coutries that are themselves far from the scene of emission have taken an interest in the phenomenon. Unfortunately, there is still much research to be done to understand the smog and its potential for global environmental impact. British experts say, in relation to the Asian cloud, that aerosols - tiny particles of pollution such as soot - are associated with sulphur dioxide and there has been a 35 per cent increase in these emissions per decade over the region. However, they also admit that not enough is known about this phenomenon to make any clear cause-and-effect pronouncements. In the absence of conclusive proof, thinly veiled accusations reign.

In December 2002, two scientists from the Centre for Atmospheric and Ocean Science at the Indian Institute of Science in Bangalore, J. Srinivasan and Sulochana Gadgil, commented on the Asian brown cloud controversy in Current Science (http://www.ias.ac.in/currsci/dec102002/1307.pdf) . They noted that instead of being a purely Asian phenomenon, the smog was present over many other regions too, albeit not as severely. Even their critics - who included four leading Indian scientists from the Indian Ocean experiment called INDOEX - concede this point. Further, it took place outside the monsoon, for obvious reasons. Srinivasan and Gadgil directed their criticism not so much at the atmospheric disturbance itself, as assessed by UNEP, but at the predictions of its impact. In 2002, the UNEP study had made much of the likely fallout on agriculture, but the Bangalore scientists point to the uncertainties in all such assessments.

Indeed, uncertainty in climate modeling has been a bone of contention earlier too, albeit in a different context. The World Resources Institute brought out a study just before Rio in 1991 showing that India, having the largest cattle population in the word, was guilty of emitting a tremendous quantity of methane (which is produced by the animals). Methane has a longer half-life in the atmosphere than carbon dioxide, and is thus thought to be an important greenhouse gas. However, when Anil Agarwal, a Delhi-based journalist and researcher, examined the science, he found that the WRI was estimating the methane emissions of cows based on a Dutch study by Crutzen. It does not require rocket science to realise that Indian cows being infinitely smaller (not to mention half-starved, for the most part!) than their Dutch counterparts, their emissions are correspondingly far smaller. Hence, what is often treated as hard science has to be examined and re-examined with careful rigour.

Taking no chances at being seen as 'the dirty country in the region', if not the world, the government decided in 2003 to launch a study to determine how far India and other countries were responsible for the brown cloud. The study, cleared by the high-power Council for Meteorological and Atmospheric Sciences, and headed by the Science and Technology Secretary, would deploy a network of what is called sky scanner radiometers across the country. The equipment, to be imported at a cost of about Rs.5 lakhs each, would be strategically placed to get as correct and complete a picture of smog over India as possible. The scientists identified the areas where they would be located: east and west coast, the north-east, Central India and the Thar Desert in Rajasthan.

While the scanners located on the coasts would provide data on the nature and quantum of the pollution that is getting transported from other regions, those in other locations would give a picture of the kind and load of pollution originating from the country, both because of industrial and other human activities and those due to natural processes such as sandstorms. While the scanners in the north-east would provide data on the pollution created because of the slash and burn practice adopted by the farmers in the region, the ones in Central India would provide information on the nature and quantum of pollution caused by other manmade activities in other parts of the country and those in the Thar Desert would assess the level of pollution whipped up by sandstorms.

But the results of these studies have not been made public. And without credible evidence and argument from such research, the finger-pointing is likely to continue. It is well known that Asian countries are guilty of inefficient combustion of fossil fuels, and whatever the country's professed views in global fora, it is important that the country tackle its extensive air pollution vigorously for its own interests. That focus, unfortunately, has been largely lost amidst the various strategic arguments.