Veerabhadran Ramanathan, who led the 1999 research into what was dubbed the "Asian Brown Cloud," said there was evidence the Gulf region was being sucked into a global pollution circuit moving several kilometres above ground.

"The Middle East has to be part of our programme because here the problem is that the dust and pollution can interact," Ramanathan said at a conference on atmospheric pollution in Dubai.

"I presumed this region was clean, but the dust haze in the desert is a lot less than here in the city. Then I saw this picture," he said, pointing to aerial shots of a cloud hanging over Dubai.

Worrisome haze

"This haze is about 300 metres above the ground, I would say. It could be coming locally or from several hundred kilometres away," he said, adding no research has been done into the effect of oil refineries along the Gulf coastline.

"The Middle East has to be part of our programme because here the problem is that the dust and pollution can interact"

Veerabhadran Ramanathan Scripps Institution of Oceanography, University of California

Ramanathan's team, backed by the United Nations Environment Programme, first identified a blanket of chemicals and dust from cars, aerosols and agricultural and industrial waste across much of South Asia in 1999.

Ramanathan, an atmospheric scientist at the Scripps Institution of Oceanography at the University of California, said the major contributors to a worldwide circle of pollution were Los Angeles, Delhi, Mumbai, Beijing and Cairo.

The Indian scientist suspects the effect of the shroud of pollution across the globe could be a drier planet.

"We are interested to see if the planet will be warmer and wetter or warmer and drier. My research suggests a large drying effect, especially in the Tropics," he said.

"The haze is reducing sunlight to the oceans and one of the things sunlight does is evaporate water from the ocean which gives us rain in the water cycle," Ramanathan said.