The long-term trend of global warming is continuing, despite the current La Nina weather phenomenon that is bringing relatively cooler temperatures to parts of the Equatorial Pacific region, says the United Nations World Meteorological Organization.

Worldwide temperatures this year are expected to be above the long-term average, though La Nina is also likely to persist through to the middle of 2008, WMO reported.

WMO Secretary-General Michel Jarraud said while there would always be both cooler and warmer individual years, the overall trend in temperatures is still upwards.

"For detecting climate change you should not look at any particular year, but instead examine the trends over a sufficiently long period of time," he said.

Parts of the central and eastern Pacific Ocean have experienced significantly cooler sea-surface temperatures in recent months, WMO reported, and cooling has also been recorded over China and West Asia.

But Australia, Russia, the western U.S., north-eastern Brazil and the southern part of South America have generally experienced higher-than-average temperatures since last December, it added.