OSLO (Reuters) - Climate change is still nudging up temperatures in the long term even though the warmest year was back in 1998 and 2008 has begun with unusual weather such as a cool Pacific and Baghdad's first snow in memory, experts said.
"Global warming has not stopped," said Amir Delju, senior scientific coordinator of the World Meteorological Organization's (WMO) climate programme.
Last year was among the six warmest years since records began in the 1850s and the British Met Office said last week that 2008 will be the coolest year since 2000, partly because of a La Nina event that cuts water temperatures in the Pacific.
"We are in a minor La Nina period which shows a little cooling in the Pacific Ocean," Delju told Reuters. "The decade from 1998 to 2007 is the warmest on record and the whole trend is still continuing."
This year has started with odd weather including the first snows in Baghdad in memory on Friday and a New Year cold snap in India that killed more than 20 people. Frost hit some areas of Florida last week but orange groves escaped mostly unscathed.
Iraqis welcomed snow as an omen of peace. "It's the first time we've seen snow in Baghdad," said 60-year-old Hassan Zahar. "I looked at the faces of all the people, they were astonished."
Last year, parts of the northern hemisphere were having a record mild winter with even Alpine ski resorts starved of snow.
Delju said climate change, blamed mainly on human emissions of greenhouse gases from burning fossil fuels, would bring bigger swings in the weather alongside a warming trend that will mean more heatwaves, droughts, floods and rising seas.
"The more frequent occurrence of extreme events all over the world -- floods in Australia, heavy snowfall in the Middle East -- can also be signs of warming," he said.
The U.N. Climate Panel said last year that global warming was "unequivocal". It said temperatures rose by 0.74 degrees Celsius in the 20th century and could rise by a "best guess" of another 1.8 to 4.0C by 2100.
The record year for world temperatures was 1998, ahead of 2005, according to WMO data. Among recent signs of the effects of warming, Arctic sea ice shrank last year to a record low.
Rajendra Pachauri, the head of the U.N. Panel that shared the 2007 Nobel Peace Prize with former U.S. Vice President Al Gore, said he would look into the apparent temperature plateau so far this century.
"One would really have to see on the basis of some analysis what this really represents," he told Reuters, adding "are there natural factors compensating?" for increases in greenhouse gases from human activities.
He added that sceptics about a human role in climate change delighted in hints that temperatures might not be rising. "There are some people who would want to find every single excuse to say that this is all hogwash," he said.
Delju said temperatures would have to be flat for several more years before a lack of new record years became significant.
He noted 2005 was the second hottest year and that 1998 was boosted by a strong El Nino event which can raise temperatures worldwide in the opposite of the La Nina cooling.
Underscoring an underlying rise in temperatures, British forecaster Phil Jones said 2001-07, with an average of 0.44 Celsius above the 1961-90 world average of 14 degrees, was 0.21 degree warmer than the corresponding values for 1991-2000.
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