Aerosol Levels Rise in India

There has been an exceptional raise in the levels of fine particles in the atmosphere over India, especially those generated by human action, according to research published recently by a team of Indian scientists. Such particles, known as aerosols, contribute to the rising levels of pollution in India.

Aerosol particles in the Earth's atmosphere scatter and soak up light differently at different wavelengths, thereby affecting the amount of incoming sunlight that reaches the planet's surface and the amount of heat that escapes, potentially altering the planet's climate.

Aerosols contain naturally occurring particles like sea-salt and dust. But concern has rising over those created by humans, such as soot from vehicle emissions and the burning of firewood and sulphate particles that spew out from thermal power stations and cement plants.

A team of scientists from the ISRO’s Space Physics Laboratory in Thiruvananthapuram, along with colleagues at the IIS in Bangalore and several universities, analysed measurements of ‘aerosol optical depth’, a index of aerosol levels, made over many years with ground-based instruments at ten stations situated in various parts of the country as well as one in the Maldives.

Over most of the stations, AOD had shown an increasing trend. Particularly striking was the change registered at Thiruvananthapuram and Visakhapatnam, where the rate of increase in aerosol levels had jumped since 2000.

Assessment of the AOD levels at four different wavelengths of light made it possible to discern fine human-generated aerosols from the coarse ones that were naturally created. The relative abundance of aerosols produced by humans had grown at both Thiruvananthapuram and Visakhapatnam, the rise being greater at the latter.

If the current trend in India of increasing anthropogenic aerosol emissions were to continue unabated, the loading of such particles in the atmosphere could double by around 2050.

The aerosol-induced warming of the atmosphere might triple as a result, which could affect the monsoon and the regional climate, observed Dr. Satheesh, one of the lead authors for the latest assessment report published by the Intergovernmental Panel on Climate Change.