Heatwave in Europe, US, but is it climate change?

The heat has already killed at least 21 people in France, including a 15-month-old baby, prompting fears of a repeat of the European heat wave in 2003 in which at least 15,000 people in France and 20,000 in Italy died.

Large parts of the United States and Canada have also seen record high temperatures this month. "We are cooking," said US meteorologist Dennis Feltgen of the National Weather Service.

Many scientists reckon the globe is warming and will continue to do so due to the "greenhouse effect" caused by emissions from fossil fuels trapping heat in the atmosphere. But they say we should not read too much into a single hot spell.

"As ever, you cannot say any one weather event is caused by global warming," said Asher Timms of Britain's Tyndall Centre for Climate Change Research. "But globally, it seems that there's quite a shift in our weather patterns."

Skeptics of the global warming theory, which predicts droughts and floods this century unless greenhouse gas emissions are curbed, say the media play up hot summer days for dramatic effect.

Bill O'Keefe, a board member of Washington think tank the George C. Marshall Institute and a consultant to the oil industry, said the record heat could be seen as part of a natural cycle of highs and lows.

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"I don't think there is any climatologist or meteorologist that would say you could draw a conclusion about any given year. There have been hotter periods in the past and we will have them in the future," O'Keefe told Reuters.

"If this persisted for a very long time than you might be able to conclude that human activities had an impact."

But many scientists say a warming trend is already clear.

US space agency NASA says 2005 was the warmest globally in more than a century and that the preceding three years were also the warmest since the 1890s.

The US National Climatic Data Centre said the first half of 2006 were the warmest six months since records began in 1895.

"NASA's averages for the world and what we produce here are far more informative than looking at the extremes in Britain, France or Italy like the summer of 2003," said Philip Jones, climate research professor at Britain's East Anglia University.

"It's the global averages that count."

"Ten of the last 12 years were the warmest since 1850. The global temperature (since then) rose 0.7 degrees Celsius and most climate models suggest it's going to continue to warm by 2 to 5 degrees Celsius this century," Jones said.

The skeptics say any warming over the last century can be explained by the fact that the planet was coming out of a cold period, known as the "Little Ice Age" and not due to a massive build-up of greenhouse gases after the Industrial Revolution.