CLIMATOLOGISTS may insist the world is getting warmer and that climate change is here to stay.
But the meteorological phenomenon called La Niña, in which the central and eastern Pacific Ocean is getting cooler, means global temperatures will drop slightly this year.
But this year's temperatures would still be way above the average - and we
would soon exceed the record year of 1998 because of global warming induced by greenhouse gases.
The phenomenon is sister to the better known El Niño, or the Little Boy, which appears when too little cold water rises to the ocean's surface, causing the planet's temperature to rise and bringing major disruption to weather systems.
La Niña has caused floods in Mozambique, and freezing temperatures in China.
David Parker, research scientist at the Met Office's Hadley Centre, which studies climate change and variation, said La Niña was part of the natural cycle of the world's seas.
"It happens of its own accord, and eventually, when it finishes, the effect wears off and the world's temperature will rise again," he said.
"While it is in effect, the world temperature will cool by a quarter of a degree, which isn't a lot, given that we've had a half to three-quarters of a degree warming already, but it's quite a chunk relative to the global warming we've had so far."
He added that though Britain had not felt the full force of La Niña's influence, it would affect the country's weather.
"It means that the climate will be colder, but it has different effects across the world," he said. "We had a mild winter this year, which to some extent goes along with La Niña.
There's also a greater than average chance of a damper summer – which I think the Met Office has already forecast – but not to the same extent as last summer. In fact, last summer's damp weather was probably connected with La Niña."
However, Mr Parker said that it was wrong to believe the drop in temperatures meant global warming was not a reality.
"You have to be very careful how you look at these figures; 1998 was an El Niño year. The current temperature was unusually warm for then. Now we have a La Niña and it's unusually cool compared with trends nowadays. If you take a trend over ten years, you don't get a warming, but that's too short a period in which to get a trend."
"In a proper long-term sense we are on a warming trend.
"The expectation is that the temperature of the world is going up and up. There's no evidence that global warming isn't happening."
The World Meteorological Organisation has pointed out that the decade from 1998 to 2007 was the warmest on record. Since the beginning of the 20th century the global average surface temperature has risen by 0.74C.
Dr Neil Wells, senior lecturer in oceanography at the National Oceanography Centre at Southampton University, said: "It is a major event because it is so vast – it is one of the major causes of weather variation. It redistributes heavy rain where you wouldn't expect it. Northern Australia tends to be affected by it. The evidence that climate change has affected it just isn't strong.
"We know this has happened for thousands of years – the flow of the Nile has been recorded as being affected by it – and that it has gone through various long period cycles, but we cannot say that climate change has been affected."
