New research reveals origin of Asia's 'brown cloud'
Researchers in Sweden, India and the Republic of Maldives have discovered that a sooty cloud of pollution that hangs over South Asia between January and March every year is created by a combination of the burning of both fossil fuels and biomass. The discovery, which used the first-ever micro-scale measurements of natural C-14 (a carbon dating method), gives the green light for action to be undertaken to reduce the cloud's insidious effects, including the thousands of deaths it causes every year. The brown cloud that covers South Asia for most of each winter is responsible for the deaths of approximately 340,000 people in India and China every year from related cardiovascular and respiratory problems. Some studies have put the figures much higher, possibly even into the millions. The cloud is also contributing to climate change in Asia and is affecting the area's climate as much, if not more, than carbon dioxide, as the soot particles in the cloud absorb sunlight, which contributes to a rise in temperature. Until now the cloud's origins have not been adequately understood. But new research recently published in the journal Science shows that two thirds of the cloud is made up of soot particles from burning and combustion methods including so-called 'slash and burn agriculture', industry, traffic, and wood fires for heating and cooking which use a variety of materials including dung, wood and crop residues. Previous research has been uncertain as to whether the origins of the brown cloud were due to the burning of fossil fuels or from biomass. To analyse the age and origin of the soot particles, a team of Swedish and Indian researchers used the first-ever micro-scale measurements of natural C-14 (carbon dating) from soot particles captured in different parts of South Asia. The results showed that two-thirds of the cloud is composed of particles from the burning of biomass and one-third from the burning of fossil fuels. Leader of the study Örjan Gustafsson, Professor of Biogeochemistry at the University of Stockholm, said the results show that efforts to reduce pollution should not be limited to traffic and coal-fired power plants, but must include eliminating poverty and helping to spread green technology in South Asia. 'More households in South Asia need to be given the possibility to cook food and get heating without using open fires of wood and dung,' he explained. Reducing soot emissions from biomass may have a positive effect on the environment very quickly. Soot causes about half the warming potential of carbon dioxide, but soot particles only remain in the atmosphere for a few weeks, meaning that a reduction in soot in the atmosphere could have a noticeable effect very quickly. Henning Rodhe, Professor of Chemical Meteorology at the University of Stockholm, said that the report's finding of over 340,000 deaths every year from the effects of the cloud should lead to action. 'The impact on health alone is a strong enough reason to reduce the brown cloud,' he noted.
Countries
China, India, Sweden