Forecasters say this one is brewing up to be the second-strongest on record
By Michael McCarthy, Environment editor
The Independent, Monday, 3 August 2009
A new El Niño has begun. The sporadic Pacific Ocean warming, which can disrupt weather patterns across the world, is intensifying, say meteorologists. So, over the next few months, there may be increased drought in Africa, India and Australia, heavier rainfall in South America and increased extremes in Britain, of warm and cold. It may make 2010 one of the hottest years on record.
The cyclical phenomenon, which happens every two to seven years, is a major determinant of global weather systems. The 1997-98 El Niño combined with global warming to push 1998 into being the world's hottest year, and caused major droughts and catastrophic forest fires in South-east Asia which sent a pall of smoke right across the region.
At present, forecasters do not expect this El Niño to equal that of 1998, but it may be the second-strongest, and concerned groups, from international insurance companies to commodity traders, to aid agencies such as Oxfam, have begun to follow its progress anxiously. Its potential for economic and social impact is considerable.
Professor Chris Folland, of the Met Office Hadley Centre for Climate Prediction and Research, said: "We are likely to see more global warming than we have seen in the past few years, which have been rather cool. In fact, we are already seeing it."
El Niño in Spanish means The Child – that is, the Christ Child – and it was named by Peruvian and Ecuadorean fishermen who first observed the phenomenon. It is a periodic warming of the normally cold waters of the eastern tropical Pacific, the ocean region westwards out from South America along the line of the equator. Since the Pacific is a heat reservoir which drives wind patterns around the world, the change in its temperature alters global weather. An El Niño is defined by ocean surface temperatures rising by more than 0.5C above the average.
This El Niño is well beyond that, says the Climate Prediction Center of the US National Weather Service. "Sea surface temperatures remain +0.5 to +1.5 above average across much of the equatorial Pacific Ocean," the centre reported last week. "Observations and dynamical model forecasts indicate El Niño conditions will continue to intensify and are expected to last through the northern hemisphere winter of 2009-10."
The last El Niño was in 2006-07 and, at its peak, sea surface temperatures averaged about 0.9 degrees above normal. But this is a stage which has already been reached by this one.
The last El Niño, comparatively weak though it was, is thought to have been partly responsible for the extraordinarily warm weather in Britain between the summer of 2006 and the spring of 2007: July 2006 was Britain's hottest month, autumn 2006 (September, October and November) was the warmest autumn, winter 2006-07 (December, January and February) was the second warmest in Britain, and April 2007 was our warmest April.
People have forgotten this because there then began our recent cooler and wetter period, with Britain's two "washout summers" of 2007 and 2008, and they may, in turn, have been associated with the counter-phenomenon of La Niña ("The Girl Child"), a cooling of the eastern tropical Pacific waters, which followed. The start of the present El Niño was one reason the Met Office predicted a "barbecue summer" for 2009, and Professor Folland said the high pressure in the Atlantic produced by it may have been a cause of the very warm June. People have also forgotten that, the warmest month since the record July in 2006. But in July the high pressure was too far to the north to affect Britain, the professor said, and this was simply part of natural weather variation.
This El Niño might produce abnormally warm weather in Britain, said Professor Folland, but it also might produce a colder winter, if it brought high-pressure systems which drew in air from eastern Europe.
Anatomy of a cyclone: El Niño and La Niña
*Usually associated with the Pacific storms it causes, El Niño is a series of changes in air pressure in the Eastern Pacific between Tahiti and northern Australia. It is triggered by a period of warming surface waters in the region every three to eight years but the forces which drive those changes are still the subject of much research.
El Niño was reportedly named after the Christ child by Spanish-speaking fisherman because they noticed it usually appeared around Christmas. It is associated with an intensification of the Madden-Julian oscillation – the eastward progression of heavy rains across the Pacific.
In recent history, it has caused tropical cyclones in the central Pacific and it has been suggested that El Niño was behind the poor crop yields in Europe which helped to spark the French Revolution in 1789.
The opposite effect to El Niño is La Niña, caused by a cooling of the surface waters of the Eastern Pacific. The two phenomena recur in a constant cycle.