A vast brown curtain of haze 10 million square kilometres in width hangs over most of the Asian continent during the tropical dry season, the Indian Ocean Experiment (INDOEX) and the United Nations Environment Programme (UNEP) have announced. Klaus Toepfer, executive director of UNEP, says the haze could have ‘profound effects on human health, crop yield and rainfall patterns in the region’. On a plane flight from Kathmandu in Nepal towards the Himalayas, scientists and UNEP staff found the haze extended vertically at least five kilometres – a mixture of pollutants from fossil-fuel consumption and burning of biomass which is reducing sunlight on the ground by 10 per cent. UNEP is looking at the combined effects of global warming and air pollution on human health and weather cycles. Nobel Prize winner Professor Paul Cruzen of the Max Planck Institute of Chemistry, who led the research with Professor V Ramanathan of INDOEX, said the challenge the haze posed was as serious as that of ozone depletion.