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La Nina caused some of the coldest temperatures in memory in China
Global temperatures this year will be lower than in 2007 due to the
cooling effect of the La Nina current in the Pacific, UN meteorologists
have said.
The World Meteorological Organisation's secretary-general, Michel
Jarraud, told the BBC it was likely that La Nina would continue into
the summer.
This would mean global temperatures have not risen since 1998, prompting some to question climate change theory.
But experts have also forecast a record high temperature within five years.
'Variability'
La Nina and El Nino are two great natural Pacific currents whose effects are so huge they resonate round the world.
El Nino warms the planet when it happens, La Nina cools it. This year, the Pacific is in the grip of a powerful La Nina.
It has contributed to torrential rains in Australia and to some
of the coldest temperatures in memory in snow-bound parts of China.
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LA NINA KEY FACTS
La Nina translates from the Spanish as "The Child Girl"
Refers to the extensive cooling of the central and eastern Pacific
Increased sea temperatures on the western side of the
Pacific means the atmosphere has more energy and frequency of heavy
rain and thunderstorms is increased
Typically lasts for up to 12 months and generally less damaging event than the stronger El Nino
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Mr Jarraud told the BBC that the effect was likely to continue into the
summer, depressing temperatures globally by a fraction of a degree.
This would mean that temperatures have not risen globally since 1998 when El Nino warmed the world.
A minority of scientists question whether this means global warming has
peaked and the earth has proved more resilient to greenhouse gases than
predicted.
But Mr Jarraud insisted this was not the case and noted that
1998 temperatures would still be well above average for the century.
"When you look at climate change you should not look at any
particular year," he said. "You should look at trends over a pretty
long period and the trend of temperature globally is still very much
indicative of warming."
"La Nina is part of what we call 'variability'. There has always been
and there will always be cooler and warmer years, but what is important
for climate change is that the trend is up."
Experts at the UK Met Office's Hadley Centre for forecasting in
Exeter said the world could expect another record temperature within
five years or less, probably associated with another episode of El Nino.
Roger Harrabin BBC
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