LONDON - Icy conditions have driven a surge in energy demand in heavily populated parts of the northern hemisphere but some countries are enjoying a relatively mild winter, data shows.

Severe weather, partly due to the El Nino weather phenomenon, has frozen parts of northwest Europe that usually escape the coldest winter temperatures, driving gas demand to records in Britain and straining French power systems. In China there are energy rations.

I think the impression is that because north Asia is cold, and parts of North America and Europe are cold people have tended to get the impression that the whole of the northern hemisphere is cold, said Robin Thwaytes, a forecaster at the Met Office, Britain's official weather center.

But that isn't the case. Generally it evens itself out in that for every area that is cold there are some areas that are very warm.

The Met Office's latest chart of global temperature anomalies indicates that Alaska and much of Canada are warmer than the long-term average for the time of year.

Freezing temperatures and heavy snow at the start of January is a shock for those parts of northwest Europe -- France and Britain -- that are usually shielded from the coldest weather that typically affects central and eastern Europe in midwinter.

HARDEST HIT

Britain, which uses gas to heat two thirds of its homes, and France which relies on electric heating are the hardest hit as the relatively mild south-westerly winds that usually blow in from the Atlantic are nudged out by Arctic winds from the north.

The weather, which has driven UK gas prices up sharply this week, is expected to last for another two weeks, draining European gas supplies.

Britain endured one of the coldest Decembers on record, with gas demand hovering near record highs this week, while average heating demand in the United States rose above the 40-year average.

French reliance on electric heating has raised the risk of power cuts in regions with longstanding supply problems, although the grid operator said there was not a threat of nationwide disruption.

French grid operator RTE said on Tuesday it had put Brittany on alert for power cuts.

But in Germany, the national weather office DWD said current temperatures were not unusual.

Such winters are normal in our latitude, although European and other northern hemisphere countries can differ a lot from each other, a DWD spokesman said.

European gas stocks are brimming because of lower drawdowns last year when the finance crisis hit industrial demand.

Private forecasters WSI warned late last year that the combination of the El Nino weather phenomenon, a cold north Pacific and cold mid-latitude North Atlantic sea surface temperatures would likely lead to cold weather in northern Europe and the United States.

Blistering cold forced cities across eastern and central China to ration power for industry -- impacting base metals production and helping to drive up copper and aluminum prices -- while residents were urged to curb gas use due to surging demand for heating.

Soaring demand, transport problems and brinkmanship over prices has also strained coal supplies, which could force more power cuts and upset production if conditions worsen.

But the climate change skeptics should not conclude that the globe is not warming.

World Meteorological Organization said last month that 2000-2009 was the hottest decade since records began in 1850, and that 2009 would likely be the fifth warmest year on record. WMO data show that eight out of the 10 hottest years on record have all been since 2000.

(Additional reporting by Vera Eckert, Gerard Wynn, Barbara Lewis, Gus Trompiz, Mohd Ramthan Hussain; editing by Sue Thomas)

Canada China Energy Climate