By Richard Black
Environment correspondent, BBC News website, Copenhagen
This year is set to be the fifth warmest on record, says the Met Office
The first decade of this century is "by far" the warmest since instrumental records began, say the UK Met Office and World Meteorological Organization.
Their analyses also show that 2009 will almost certainly be the fifth warmest in the 160-year record.
Burgeoning El Nino conditions, adding to man-made greenhouse warming, have pushed 2009 into the "top 10" years.
The US space agency Nasa suggests that a new global temperature record will be set "in the next one or two years".
World Meteorological Organization (WMO) and Met Office scientists have been giving details of the new analysis at the UN climate summit in Copenhagen.
The WMO said global temperatures were 0.44C (0.79F) above the long-term average.
"We've seen above average temperatures in most continents, and only in North America were there conditions that were cooler than average," said WMO secretary-general Michel Jarraud.
"We are in a warming trend - we have no doubt about it."
Mr Jarraud emphasised that the final analysis would not be complete until early next year; but the UN agency always issues a summary during the annual climate negotiations in order that delegates have the latest information.
The WMO uses three temperature sets - one from the UK Met Office and the University of East Anglia's Climatic Research Unit (CRU), and two from the US, maintained by the National Oceanic and Atmospheric Administration (Noaa) and the space agency Nasa.
Asked whether the controversy surrounding e-mails hacked from CRU could have any bearing on the results, Mr Jarraud replied that all three datasets showed the same result.
Vicky Pope from the UK Met Office made the same point: "The datasets are all independent, and they all show warming," she said.
The Met Office figures indicate that the years since 2000 - the "noughties" - were on average about 0.18C (0.32F) warmer than years in the 1990s; and that since the 1970s, each decade has seen an increase of about the same scale.
Although the Met Office has 1998 as the single warmest year, that coincided with strong El Nino conditions - the warming of surface waters in the eastern Pacific that releases heat stored in the deep ocean into the atmosphere, raising temperatures globally.
Now, after a period of La Nina conditions which depressed temperatures in 2008, another El Nino is developing; and it is this, combined with greenhouse warming, that is pushing temperatures upwards again, according to Dr Pope.
She declined to give a forecast for the next few years - the Met Office is releasing that later during this summit.
But Nasa's GISTEMP unit - the division of the agency that maintains the temperature dataset - suggests further warming is coming, with the temperature record for an individual year likely to be set within the next year or two.
This decade 'warmest on record'
Other researchers, though, believe it more likely that temperatures will remain stable for up to a decade as other natural cycles keep the ocean's surface relatively cool, with rapid warming likely after that.
Climate "sceptics" have claimed that temperatures have not been rising over the last decade. Of the two widely-used global temperature records, one - the UK HadCRUT3 record - shows an apparent plateau from 1998 to 2008.
But climate scientists point out that this result is achieved by taking 1998 as the starting point. Taking, for instance, 1997 or 1999 as the starting point, they argue, produces a different result.
In a separate move, the Met Office has released data from more than 1,000 weather stations that make up the global land surface temperature records.
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