Origin of deadly cloud revealed
Not so much a pea-souper as a mushroom-coloured fog, a huge brown cloud of pollution can be seen hanging over South Asia and the Indian Ocean during the winter months. And it doesn't just block the light - it can be deadly, causing deaths from heart and lung disease, and even cancer in China and India. Plus, it's thought to cause global warming and climate change in the area.
Although scientists have known about the cloud for some time, its origins have been a mystery - is it caused by soot from burning wood and dung, or is it due to fossil fuels?
Writing in the journal Science this week, Örjan Gustafsson and his colleagues in Sweden, the Maldives and India have analysed the cloud from a mountaintop in western India, and from the honeymoon island the Maldives using radiocarbon techniques.
The scientists discovered that the main culprit in the cloud - making up about two-thirds of it - is soot from burning organic matter, known as biomass. This includes wood and dung that are used for cooking and heating in homes across Asia.
The researchers suggest that cutting down on burning biomass will have a huge impact on air quality, climate change, and potentially health in the region. They think that the finger is being unfairly pointed at cars and coal-fired power stations, and in fact governments and other organisations should be thinking more about bringing appropriate green technologies for home cooking and heating to countries such as India.
And because the soot particles from burning biomass only hang around in the atmosphere for a few weeks, making such changes should he a rapid effect on climate and air quality.