Environment: Greenhouse gas linked to weather system

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"To me, it's just the like a pot on the fire," says Bekuretsion Kassahun. "You think the heat is being distributed evenly, but there's always one part which heats up more quickly than the rest. That's what El Nino is - I believe that it's caused by global warming, and that it's just the first place, the very beginning of the effects which are going to be felt."

Mr Kassahun is probably in a minority at the environment conference in Kyoto - science has yet to establish an indisputable connection between El Nino and the warming of the planet caused by carbon dioxide emissions. But, as a meteorologist for the Ethiopian government, he has more immediate reason to worry than most. This year, southern Ethiopia has suffered devastating floods which have killed more than 100 people and displaced up to 200,000 others. In neighbouring Somalia, the situation is many times worse. And there is little doubt that the rains are the result of a rise in the temperature of the Indian Ocean caused by El Nino.

What causes El Nino is another matter, and the official literature is tantalisingly vague. According to the United Nations' World Meteorological Organisation which gave a presentation on the subject in Kyoto yesterday, "it is the very complex interaction between the ocean and the atmosphere that determines the onset and termination of El Nino events."

Huge volcanic eruptions which block out the sun with large quantities of ash may or may not influence them, and a link between El Nino and global warming "has not been confirmed by research". But if the mounting consensus among scientists about the progress of global warming is correct, then El Nino may very well be giving a foretaste of what the world has in store.

If greenhouse gases, principally carbon dioxide, double by the end of the next century, average temperatures could rise by 3.5C, with correspondingly dramatic consequences. Greenhouse gas emissions have increased steadily throughout the 20th century and so have the intensity and frequency of El Nino "events".