The flow of warm water south along the east Pacific coast, replacing the normal upwelling of cold water from the Southern Ocean, was much more extensive this winter than in normal years. In a report last week, the National Oceanic and Atmospheric Administration said the 1997-98 El Nino ranks as one of the major climatic events of the century. "Last winter gave the world a preview of what climate conditions may be like as global warming increases,'' Mr Baker said.
Some models, he said, indicate that with global warming the effects of El Nino will intensify, but he admitted there was no hard evidence this was happening.
The key words are "some models''. Attempts to model the climate using super-computers, desktop Pentiums or pen and paper have not been successful.
El Nino is driven by solar heat. If the total thermal input into the system increases, say as a result of carbon dioxide-induced warming, it might be expected that effects such as El Nino would increase. But it might also be expected that other thermal phenomena, such as tropical storms, would increase too. In fact, the severe El Nino of the past few months has been directly related to a fall in both the number, and severity, of tropical Atlantic storms.
It's all horribly complicated, and it's probably fair to say that inferences of catastrophic change from a few months' worth of data should be treated with extreme caution.