Climatologists seek clear view of Asia's smog

Project to assess climate impact of massive brown clouds.


Foggy notion: Asia's hazy smog comprises fumes from forest fires (yellow) and pollution from populated areas (white). Credit: JAXA

An international team gathered in South Korea this week to kick off a research project on Asia's persistent brown clouds of smog. The effort is the first long-term study into the effects of the haze on local and global climate.

The brown clouds frequently envelop vast portions of Asia. They wax and wane with the seasons but can be kilometres thick, causing respiratory disease and interrupting climate cycles.

Researchers on Project Atmospheric Brown Clouds, run by the United Nations Environment Programme (UNEP), are hoping that their study of the smog will help to spur preventative measures against the pollution. This could be especially important in the face of China's accelerating industrial boom.

The clouds consist of ash, acidic chemicals and carbon, which come from the burning of fossil fuels and wildfires. One of the most intensely polluted and most studied brown clouds, which hangs over the Indian Ocean, has recently been found to consist largely of the smoke from dried manure used for cooking (C. Venkataraman et al. Science 307, 1454–1456; 2005).

Previous research has shown that the haze over the Indian Ocean blocks up to 15% of the Sun's radiation (S. K. Satheesh and V. Ramanathan Nature 405, 60–63; 2000). Such clouds are thought to cause the ground to cool and the atmosphere to warm, which can affect monsoons and other rainfall patterns. Particulate matter can also alter rain formation. But little is known about the details of how the clouds change over time, or how this alters the climate, says Veerabhadran Ramanathan, an atmospheric scientist at the Scripps Institution of Oceanography in La Jolla, California, who is involved with the UNEP project. “We need to watch the whole seasonal cycle for several years,” he says. “There have been many theories about how this affects global climate. We have to observe it.”

The UNEP project aims to follow the Asian clouds for at least five years; funding of US$10 million has been secured for this period from the US National Oceanic and Atmospheric Administration and the National Science Foundation. The programme has two main observatories: one in the Maldives and one on the Korean island of Jeju. Each is stocked with more than 30 instruments that can measure incoming sunlight, temperature and the chemical composition of the clouds. Tens of smaller labs throughout the region will also contribute data.

The scientists involved say they are particularly concerned that the industrial boom and desertification currently going on in China are throwing ever more smog ingredients into the atmosphere. “East Asia might have more surprises than India — it is of a greater concern,” says Ramanathan.

But the attempt to study China's impact on the clouds could become politically sensitive. Japanese scientists estimate that some 30% of the soot falling on their country comes from China, whereas Chinese researchers place the estimate as low as 5%. “There is no consensus,” says Yuanhang Zhang, an atmospheric chemist at Peking University who is representing China in the UNEP project.

Shiro Hatakeyama, a specialist in atmospheric chemistry at the National Institute for Environmental Studies in Tsukuba, north of Tokyo, says that China has not provided sufficient information about its emissions to feed into models that predict the effects of the smog. “So far, China's efforts are not satisfactory,” says Hatakeyama.

Zhang admits that there is a lack of data for most pollutants other than sulphur dioxide in China, making it hard to assess their contribution to the haze. Hatakeyama hopes that the project will put pressure on China to collect and provide more information.

That may already be happening. Zhang says that there are plans to set up about ten observatories in the country to contribute to the programme — a meeting is scheduled for April to work out the details.


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Cyranoski, D., Fuyuno, I. Climatologists seek clear view of Asia's smog. Nature 434, 128 (2005).

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