April 4, 2008
La Nina Slows Global Warming
UN meteorologists say the cooling effect of the La Nina current in the Pacific will cause global temperatures to drop slightly this year.
Michel Jarraud, secretary-general of the World Meteorological Organization, said it was likely that La Nina would continue into the summer.
Global temperatures haven't risen since 1998, leaving many to question the climate change theory.
However, experts say we are still clearly in a long-term warming trend and new record high temperatures are forecasted within five years.
According to the WMO, 1998 to 2007 was the warmest decade on record and the global average surface temperature has risen by 0.74C since the beginning of the 20th century.
La Nina and El Nino are two great natural Pacific currents whose effects resonate around 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 that has contributed torrential rains in Australia and some of the coldest temperatures in memory in snow-bound parts of China.
Jarraud said the effect was likely to continue into the summer, depressing temperatures globally by a fraction of a degree"”meaning temperatures have not risen globally since 1998 when El Nino warmed the world.
Some scientists say this could mean global warming has peaked and that the Earth has proved more resilient to greenhouse gases than predicted.
But Jarraud insists this is not the case and noted that 2008 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; the climate on average is warming even if there is a temporary cooling because of La Nina."
China was plagued with heavy snow in January.
"The 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," said Adam Scaife, lead scientist for Modelling Climate Variability at the Hadley Centre in Exeter, UK.
"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," said Scaife.
On the Net:
World Meteorological Organization: http://www.wmo.ch/