This year is currently rated as the second warmest ever, with an increase of 0.48 degrees Celsius over the 1961-1990 annual average surface temperature that is used as the benchmark for climate change measurements, the WMO said in a statement.

In a year marked by record hurricanes in the Caribbean and melting ice floes in the Arctic, the WMO said the world experienced the warmest months of June and October ever, surpassing those recorded in 1998 and 2004 respectively.

Gaps in data and outstanding readings for the final weeks of 2005 mean that this year overall could vary from being the warmest ever to being the eighth warmest when the final figure is released next February.

"It could well be that this ranking could be modified but we are very confident that it will end up in the four warmest years," said WMO Secretary General Michel Jarraud.

"In the northern hemisphere it will be the warmest year on record and in the southern hemisphere we anticipate that it will be the fourth warmest on record," he told journalists.

The WMO emphasised in its statement on the global climate in 2005 that "the last ten years (1996-2005), with the exception of 1996, are the warmest years on record".

"Areas of significant warmth were widespread, with large areas of Africa, Australia, Brazil, China and the United States showing significantly above-average temperatures," the statement said.

Sea surface temperatures in the north Atlantic, where scientists recently warned that warm waters were melting ice floes in the Arctic Circle, are likely to be the warmest on record, the WMO added.

The agency said the extent of sea ice in the Arctic dropped by 20 percent compared to average and reached the lowest coverage observed since satellite observation began in 1979.

Jarraud confirmed that the hurricane season in the United States, Caribbean and central America "was exceptional by any measure" this year, although there were fewer typhoons in the Pacific Ocean than usual.

The 26 named storms in the Atlantic exceeded the previous high of 21 in 1993 and included the strongest ever recorded, Hurricane Wilma.

2005 is likely to be the hottest year in Australia since records began in 1910, while several parts of south Asia experienced extreme heatwaves or heavier than usual monsoons.

East Africa was blighted by continuing long term drought extending from Kenya south to Mozambique and Zimbabwe, which left several million people exposed to hunger.

Scientists fear that those extreme weather conditions are signs of climate change caused by growing emissions of greenhouse gases by industry, transport and households.

"At this stage the honest scientific answer for hurricanes is that we don't know," the global met chief said, although he highlighted evidence that the Caribbean Sea was warming and producing more frequent, intense hurricanes.

"What we feel more confident with, is that global warming will lead to more frequent heatwaves."

"Conversely there's also a risk of higher precipitation in regions where floods can be a problem," Jarraud added.

Global average temperatures over land have risen since the beginning of the 20th century, but meteorologists observed sharper rises from the late 1970s.

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