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Paris: As Russia battles wildfires triggered by an unprecedented heatwave, flood waters surge across a drenched Pakistan leaving millions of people homeless, and questions are asked about global warming.

Extreme weather has been a feature of the summer of 2010, with floods in Pakistan, China and Eastern Europe seemingly matched by heatwaves in Western Europe and Russia.

However, experts interviewed Monday were cautious over offering the events as proof of a changing climate, saying that while they fit with climatic projections in a warming planet, one extremely dry — or wet — summer isn’t sufficient evidence in isolation.

“One cannot conclude 100 percent that nothing like this has happened in the past 200 years, but the suspicion is there. Even if it’s only a suspicion,” said Jean-Pascal van Ypersele, vice-president of the Intergovernmental Panel on Climate Change (IPCC), which has tracked the impact of human activity on climate for the past 20 years.

“These are events which reproduce and intensify in a climate disturbed by greenhouse gas pollution,” he said.

“Extreme events are one of the ways in which climatic changes become dramatically visible.”

The planet has never been as hot as it has been in the first half of this year, the US National Oceanic and Atmospheric Administration said in a July report.

According to the IPCC, droughts and heatwaves likes those affecting Russia and 18 US states become longer and more intense in a warming planet.

“Whether in frequency or intensity, virtually every year has broken records, and sometimes several times in a week,” said Omar Baddour, who tracks climate change for the World Meteorological Organisation.

“In Russia, the record temperature in Moscow (38.2 degrees Celsius, 100.8 degrees Farenheit in late July) — which had not been seen since records began 130 years ago — was broken again at the start of August. In Pakistan, the magnitude of the floods is unheard of,” he said.

“In both cases, it is an unprecedented situation. The succession of extremes and the acceleration of records conform with IPCC projections. But one must observe the extremes over many years to draw conclusions in terms of climate,” he said.

The floods in Pakistan could be caused by La Nina — the inverse of the El Nino phenomenon, which it generally follows — namely the cooling of surface temperatures in the Pacific Ocean, Baddour said.

“In general, El Nino leads to drought in the Indian subcontinent and the Sahel. With La Nina, it is the opposite,” said Baddour.

According to British climatologist Professor Andrew Watson, the high temperatures this summer are linked to last year’s El Nino.

“We know that in a period following El Nino you got a very hot year globally and that is certainly occurring this year,” he said.

Nevertheless, Watson said the extreme events are “fairly consistent with the IPCC reports and what 99 percent of the scientists believe to be happening.”

Watson, who is from the University of East Anglia which was at the centre of last year’s “climategate” scandal over faked data, was reluctant to leap to any conclusions.

“I’m quite sure that the increased frequency of these kind of summers over the last few decades is linked to climate change,” he said

“But you cannot say a single event or a single summer is unequivocally due to climate change — by definition it’s weather, and not climate.”

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