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Global temperatures 'to decrease' Global temperatures 'to decrease'
(about 23 hours later)
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. By Roger Harrabin BBC News environment analyst
The World Meteorological Organisation's secretary-general, Michel Jarraud, told the BBC it was likely that La Nina would continue into the summer. La Nina caused some of the coldest temperatures in memory in China
Global temperatures will drop slightly this year as a result of the cooling effect of the La Nina current in the Pacific, UN meteorologists have said.
The World Meteorological Organization'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.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. But experts say we are still clearly in a long-term warming trend - and they forecast a new record high temperature within five years.
'Variability' The WMO points 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.
While Nasa, the US space agency, cites 2005 as the warmest year, the UK's Hadley Centre lists it as second to 1998.
Researchers say the uncertainty in the observed value for any particular year is larger than these small temperature differences. What matters, they say, is the long-term upward trend.
Rises 'stalled'
LA NINA KEY FACTS La Nina translates from the Spanish as "The Child Girl"Refers to the extensive cooling of the central and eastern PacificIncreased sea temperatures on the western side of the Pacific mean the atmosphere has more energy and frequency of heavy rain and thunderstorms is increasedTypically lasts for up to 12 months and generally less damaging event than the stronger El Nino
La Nina and El Nino are two great natural Pacific currents whose effects are so huge they resonate round the world.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. 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.It has contributed to torrential rains in Australia and to some of the coldest temperatures in memory in snow-bound parts of China.
LA NINA KEY FACTS La Nina translates from the Spanish as "The Child Girl"Refers to the extensive cooling of the central and eastern PacificIncreased sea temperatures on the western side of the Pacific means the atmosphere has more energy and frequency of heavy rain and thunderstorms is increasedTypically lasts for up to 12 months and generally less damaging event than the stronger El Nino
Mr Jarraud told the BBC that the effect was likely to continue into the summer, depressing temperatures globally by a fraction of a degree.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.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. Watching trends
But Mr Jarraud insisted this was not the case and noted that 1998 temperatures would still be well above average for the century. A minority of scientists question whether this means global warming has peaked and argue the Earth has proved more resilient to greenhouse gases than predicted.
"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." Animation of El Nino and La Nina effects
"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." But Mr Jarraud insisted this was not the case and noted that 2008 temperatures would still be well above average for the century.
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. "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; the climate on average is warming even if there is a temporary cooling because of La Nina."
China suffered from heavy snow in January
Adam Scaife, lead scientist for Modelling Climate Variability at the Hadley Centre in Exeter, UK, said their best estimate for 2008 was about 0.4C above the 1961-1990 average, and higher than this if you compared it with further back in the 20th Century.
Mr Scaife told the BBC: "What's happened now is that La Nina has come along and depressed temperatures slightly but these changes are very small compared to the long-term climate change signal, and in a few years time we are confident that the current record temperature of 1998 will be beaten when the La Nina has ended."