Tyrants of the world beware - El Nino is back

The return of the powerful weather system could quench political hotspots. Geoffrey Lean on nature's unlikely freedom fighter

Robert Mugabe should be scouring the heavens. Top scientists predict that the weather may succeed where international pressure and internal opposition have failed, and bring him down.

The cloud – at present no bigger than a man's hand – on the Zimbabwean president's horizon is a little-noticed announcement last week that a new El Niño is on its way. The World Meteorological Organisation is forecasting that the world-wide weather-disrupting phenomenon will return next year.

The problem for Mr Mugabe – and his 11.2 million people – is that Zimbabwe is almost always one of the countries that suffers most when El Niño strikes. More than four out of every five times that the weather system returns, the country is hit by drought; in the mid-1990s the aftermath of one El Niño is estimated to have cut its economy by 12 per cent.

There is such a close link between it and maize harvests in the country that scientists have been able to predict the state of Zimbabwean harvests for the past 20 years with a high degree of accuracy by studying the sea surface temperatures in the Pacific that turn El Niño on and off.

The country's agriculture is already in deep trouble. After months of denials, its government admitted last Monday that it faced a food shortage. Bread prices have already quadrupled this year, and the finance minister, Simba Makoni, has told MPs that land seizures have helped cause a 54 per cent reduction in the planting of maize, which contributes 90 per cent of its grain harvest.

Dr Michael Glantz of the National Centre for Atmospheric Research in Boulder, Colorado – a leading expert on the phenomenon – said last week: "El Niño may, or may not, be the straw that breaks Mugabe's back, but, as sure as hell, it is going to put him under a lot of pressure."

Dr Glantz, who this month is holding a special conference at New York's Columbia University on political flashpoints likely to be affected by the weather, warns that there will quite a few troublespots with reason to fear El Niño's return.

Take Fiji. Its court of appeal this year declared its military government illegal, and it is also likely to be hit by drought. So too is Ethiopia. And Peru, where a newly inaugurated president has inherited a country in crisis, is expected to suffer devastating floods.

Indeed, the repercussions will be felt world-wide. During an El Niño, warm water flows eastward across the Pacific, bringing heavy rain with it from Indonesia to South America. The phenomenon was first identified in Peru, where it got its name – "the Christ child" – because it normally appears around Christmas-time.

All El Niños have slightly different effects. But the west coast of the United States, and most of central and southern America, are almost certain to get heavy rain. And southern and north-east Africa, Indonesia and the Philippines can normally expect drought.

Other places benefit. The Caribbean and south-east US experience fewer hurricanes during El Niños; Canada and the northern US enjoy warmer winters, but Europe is relatively unaffected.

Elsewhere, researchers at London, Barcelona and Maryland and Cornell universities have identified a surge of cholera cases in Bangladesh about 11 months after the start of each El Niño; higher sea temperatures and increased flooding are thought to encourage plankton that carry the cholera bacteria.

No one knows for certain what causes El Niños, but they appear to be becoming more frequent. Again, it is difficult to be certain, because systematic measurements of them only started in the 1980s, but all the evidence suggests that they were infrequent before 1975 and have become much more common since. The 1990s were almost dominated by four of them.

Recent research in the Eastern Pacific on coral skeletons – which undergo chemical change as the sea warms up – is revealing a longer-term record. Professor Gerard Wellington, of the University of California, who has studied corals around the Galapagos Islands, says they show El Niños occurring about every six years in the late 1600s, every four-and-a-half years around 1750, every 3.4 years around 1870, and every 2.2 years since the 1970s.

Professor Wellington believes global warming is exacerbating the phenomenon, saying: "We all know now there is a link." And that means a there's a stormy time ahead for many governments.

How weather blows history

Fall of the Mayans, c900: Mayan civilisation was probably wiped out by a drought, which evidence shows could have lasted up to 150 years.

Genghis Khan, 1279 and 1281: Genghis Khan twice tried to invade Japan. Both times he was turned back when a typhoon wrecked the Mongol fleets. This miraculous wind was named the kamikaze or "divine wind".

Battle of Crécy, 1346: Accounts of one of the most devastating battles of the Hundred Years War say a "great rain" fell before it. This could well have accounted for the French defeat, because their crossbows would have had their strings dampened, making them misfire.

Spanish Armada, 1588: After meeting the English in battle, strong winds forced the Armada north around Scotland, where gale-force winds scattered the fleet at Cape Wrath.

Napoleon and "General Winter", 1812: The march of the French emperor was eventually halted in Russia. Having captured Moscow, Napoleon delayed and was met with a Russian winter from which only a fragment of his army survived.

Irish Potato Famine, 1845: Not only did it result in the death of a million people but also shaped Irish history for many years. The blight fungus is carried by wind and thrives in heavy rain.

Research by Owen Lean