El Nino 'could mean bitter winter'
A weather event is brewing in the Pacific that could have a major impact on global agriculture and may bring bitter winter conditions to the UK, experts predict.
Forecasters at the Met Office say there is a 70% chance of a "moderate" El Nino event towards the end of this year that is likely to lead to droughts and crop failures.
The possibility of an event strong enough to affect British weather is slimmer but has not been ruled out. If this occurs, next winter could be unusually dry, cold and snowy in the UK.
Professor Adam Scarfe, from the Met Office Hadley Centre, said: "It could be big, it's possible. We're getting a pretty strong signal."
El Nino events occur on average every three to four years and are marked by a build up of warm water in the eastern Pacific off the coast of Ecuador.
They can have a major impact on weather systems and climate, reducing monsoon rainfall in many parts of the tropics, triggering droughts in India and Africa, and disrupting food production.
El Ninos do not tend to have a direct effect on the weather of northern Europe. But large events such as those that occurred in 1997/98 and 2009/2010 can set off an atmospheric chain reaction that weakens the jet stream, a ribbon of strong high wind known to have a big influence on our weather. This can lead to bitter British winters that are dry but produce large amounts of snow.
Last year some forecasters predicted an El Nino but the expected event never occurred.
This year experts around the world are far more certain that an El Nino event has already started and is likely to grow.
Professor Eric Guilyardi, from the National Centre for Atmospheric Science at the University of Reading, said: "Forecasters around the world agree that El Nino is occurring and will continue for the next few months.
"It is still possible that the event will die away, as it did last year, although the situation has already moved further on this year as the atmosphere has begun to react to the warmer waters.
"What is unusual this year is just how early it has begun. Sea surface temperatures are already 1.5C higher than expected in some parts along the equator - a level which has not been seen this early in any El Nino since 1987."
Prof Scarfe added: "I think there is very good agreement across the different centres that this is coming. It's likely there will be at least a moderate El Nino this year."
Even if the predicted El Nino has no influence on the UK weather, its economic effect could be significant, say the experts.
Dr Nick Klingaman, also from the University of Reading, said: "People around the world, including in Britain, may see the impact of El Nino in other ways. A strong El Nino is likely to substantially disrupt global food markets, increasing prices for staple foods and threatening lives and livelihoods in tropical countries.
"A moderately strong El Nino in 2002 was associated with a 22% reduction in summer monsoon rainfall in India, including a 40% reduction in rainfall during the peak of the monsoon in July. The drought devastated Indian agriculture, including groundnut and rice crops, with an estimated 15 billion US dollar (£9.64 billion) in lost produce - the equivalent of 3% of India's entire gross domestic product."
Coffee plantations in Brazil, already brought to the brink of failure by a multi-year drought, could also be hit hard, he said. In addition, an El Nino event was likely to reduce rainfall in the tropical north and east of Australia, where most of the country's banana and sugar cane crops are grown.
El Nino events also temporarily exacerbate the effects of global warming. For every 1C rise in sea surface temperature caused by El Nino, average global temperature is expected to rise by 0.1C the following year.
Scientists believe extreme El Nino events, such as the one in 1997/98, may occur twice as often after 2050 if greenhouse gas levels in the atmosphere continue to rise at their current rate.