Clearing the cloud

The Asian Brown Haze, a two-mile thick blanket of pollution comprising ash, acids, aerosols and other pollutants, stretching thousands of mi...

The Asian Brown Haze, a two-mile thick blanket of pollution comprising ash, acids, aerosols and other pollutants, stretching thousands of miles over south Asia, is in the news.

Atmospheric haze is not a new phenomenon. In winter, a haze engulfs parts of northwest India. Tiny suspended particles in the atmosphere, called aerosols, form a sheet of varying thickness, causing a lack of transparency in the air. These tiny particles could be of liquid or solid matter. If the moisture in the atmosphere is high, then the haze is dominated by water vapour and is known as a moist haze. If the atmosphere is dry and the suspended particles are of smoke or dust, then it called a smoke or dust haze.

As you climb higher from the ground, temperatures usually decrease. There are occasions, however, when in some portions of the lower atmosphere the temperatures start increasing with height and this is called inversion. The haze layers are generally found in these areas of inversion.

Some four years ago, uncontrolled forest fires in Indonesia left large parts of Southeast Asia blanketed in a smoke haze. It was an environmental disaster and cost the region an estimated 4bn. Today, at the Johannesburg Earth Summit minus Bush, the focus seems to be on the Asian Brown Haze. The controversy has erupted because of an UN report, based on the biggest ever scientific study of the phenomenon, involving 200 scientists. According to the report, this dense cloud cuts the amount of sunlight reaching the ground by 10 to 15 per cent, with adverse effects.

The study believes that the haze is caused by industrial and fossil fuels as well as by biomass burning which is the main cause for the haze. Biomass burning is an age-old procedure of burning forests for clearing land and burning fields after the harvest. If these processes have been followed for years why should there be a haze all of a sudden?

As far as India is concerned, monsoon activity 8212; limited though it was 8212; should have washed off the haze. There have also not been any reports of large-scale forest fires like those that occurred in Indonesia, neither have there been major changes in agricultural patterns or even significant demographical shifts. Can Asians then be blamed on evidence cited in just one study? Incidentally, the Asian Brown Haze is also being seen as the reason for the failure of the monsoon this time. It is difficult to accept that a two-mile thick layer will affect a synoptic scale circulation called the monsoon circulation, which is dependent on numerous parameters.

This is not to argue that the Asian Brown Haze is the figment of the imagination. Satellite imagery definitely indicates its presence. But it would be inadvisable to jump to any premature conclusions about it. There is a need, therefore, for Indian scientists to inquire into the causes behind this huge toxic cloud, watch its behaviour and study its impact.