In the wake of an international meeting on climate change, the head of the United Nations Environment Programme (UNEP) today emphasized the need to develop a more complete picture of the roles and interactions of greenhouse gases, aerosols and ozone.
Klaus Toepfer's comments came against the background of last week's Nairobi meeting of the Intergovernmental Panel on Climate Change (IPCC), which assesses the scientific, technical and socio-economic information relevant for understanding the risk of human-induced climate change.
They also followed Mr. Toepfer's visit to Kathmandu where he was briefed by the chief scientists of the Indian Ocean Experiment (INDOEX), a field mission to collect data on the regional cooling effect of sulfate and other aerosols, according to a statement released today by UNEP.
"Their research suggests that the thick brown haze which forms over much of Asia during the tropical dry season could have profound effects on human health, crop yield and rainfall patterns in the Asian region," Mr. Toepfer said.
Led by Prof. Paul Crutzen of the Max Planck Institute of Chemistry and Prof. V. Ramanathan of the Scripps Institution of Oceanography, University of California in San Diego, INDOEX involved 250 scientists from the United States, Europe and India. In a $25 million field experiment, atmospheric measurements were taken from ships, aircraft, satellites and ground-based instruments around the tropical Indian Ocean in 1999.
The results show that the brown haze - a mixture of pollutants, mainly soot, sulfates, nitrates, organic particles, fly ash and mineral dust, formed by fossil fuel combustion and rural biomass burning - is reducing the amount of sunlight reaching the tropical Indian Ocean surface, thousands of kilometres from its source, by as much as 10 per cent. The researchers tracked the haze over an area of about 10 million square kilometres, and believe it forms over much of the Asian continent, home to more than half the world's people.
The scientists plan to establish a network of ground-based monitoring stations throughout Asia to study the composition and seasonal pattern of the haze. UNEP has pledged to facilitate the continued research programme and, in the longer term, look to coordinate policy responses to address the problem.