Many scientists are predicting that this year's El Niño event will be the worst on record, bringing devastating weather to many parts of the world. Richard Black of BBC Science reports.

As usual when natural disasters loom, the world looks to science for some answers. With El Niño, the climatic phenomenon named after the Spanish term for 'Christ Child', the world is unlikely to find any.

We know that the phenomenon usually happens every seven years or so and that the effects are felt all through the tropics.

Dr Mike Davey of Britain's Meteorological Office said: "The El Niño has a specific pattern associated with it. For example, on the west Pacific side, in countries like the north-eastern part of Australia, the Philippines and Indonesia, they will be expecting much less rainfall than usual this year.

"At the other side of the Pacific, the eastern side, countries such as northern Peru, Ecuador and Bolivia are at a high risk of high rainfall and flooding."

An El Niño starts when, for some as yet unkown reason, warm water flows into areas of the Pacific Ocean which are usually cool, disturbing the usual pattern of ocean currents and trade winds. This, says Mark Saunders, a climatologist at University College in London, changes the places where rain falls.

"Where the warm water resides affects the circulation patterns in the whole atmosphere of the tropical Pacific. In particular, the air is more moist above water which is warmer, and hence it rains more in these areas. And so the regions of highest rainfall move from the west side of the Pacific towards Peru and Ecuador on the east side because that's where the warm water is," he said.

This year's El Niño has been blamed for the hurricanes in Central America and for the drought which has prolonged the smog in Indonesia, though in truth it is one factor rather than the sole cause in both.

El Niño has been blamed for prolonging the smog from the Indonesian fires

Some scientists believe it may even affect Europe, though suggestions that it will cause an especially severe winter in Russia are probably fanciful.

What we cannot do is predict with any accuracy the severity of these events. Early indications were that this year's El Niño would be severe, because the warming of the Pacific water was greater than usual.

Peter Ambenje, a climatologist at the Drought Monitoring Centre in Nairobi, said: "We have been comparing this year with what happened during the last bad El Niño year, 1982-83. The indices which determine the severity are more significant this year."

But we cannot be sure just how bad things will be. We also do not understand how the phenomenon interacts with global warming.

The scientific consensus is that El Niños will become more severe and possibly more frequent on a warmer planet, but it is not proven.

To the people already suffering the consequences of this year's event these uncertainties are hardly reassuring. Two thousand deaths and $13bn worth of damage were blamed on the El Niño in 1982 and 1983, and if we could tell when and where destruction is going to occur this time, action could be taken to ameliorate it.

Hartmut Grassel, head of the UN's World Climate Research Programme, says there are things people can do, given enough warning. For example, Peruvians change the crops they plant - switching from maize to rice.

"They may change the pattern for fishing from small boats in coastal areas to larger ones which can go into the ocean," he said. "But this needs information months ahead."

In Australia, some farmers are using a computer program that predicts patterns of rainfall. In California, public officials are telling residents to prepare "disaster kits" - bags containing emergency food, first aid materials and a torch in case floods strike.

Our ability to deal with El Niño is improving but the world's climate is a hugely complex system, and the kind of long-term predictions we really need remain well beyond our best scientists.

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