One of Europe's leading scientists on Tuesday raised the possibility that the extreme heat wave now settled over at least 30 countries in the northern hemisphere could signal that man-made climate change is accelerating.
"The present heat wave across the northern hemisphere is worrying. There is the small probability that man-made climate change is proceeding much faster and stronger than expected," said Professor John Schellnhuber, former chief scientific adviser to the German government and now head of the UK's leading group of climate scientists at the Tyndall center.
Schellnhuber said "the parching heat experienced now" could be consistent "with a worst-case scenario [of global warming] that nobody wants to come true."
He warned that several months' research would be needed to analyze data from around the world before scientists could say why the heat waves are so intense this year.
"What we are seeing is absolutely unusual," Schellnhuber said. "We know that global warming is proceeding apace, but most of us were thinking that in 20 to 30 years time we would be seeing hot spells [like this]. But it's happening now. Clearly extreme weather events will increase."
Other climate scientists across Europe suggested the present heat wave was perhaps the most intense experienced and linked to global warming.
"We've not seen such an extended period of dry weather [in Europe] since records began," said Michael Knobelsdorf, a meteorologist at the German weather service. "What's remarkable is that these extremes of weather are happening at such short intervals, which suggests the climate is unbalanced. Last year in Germany, we were under water. Now we have one of the worst droughts in human memory."
Antonio Navarra, chief climatologist at Italy's National Geophysics Institute, said the Mediterranean region was 2?C to 3?C warmer than usual this summer.
Temperatures across parts of Europe have been a consistent 5?C warmer than average for several months, but the heat waves have extended across the northern hemisphere. Temperatures in some Indian states reached 45?C to 49?C, with more than 1,500 people dying as a direct result. There have been near-record temperatures in Canada and the US, Hawaii, China, parts of Russia and Alaska.
The intense heat in some places has given way to some of the most severe monsoon rains on record, a phenomenon also consistent with climate change models which predict extremes of weather. The heat waves are fuelling concern that climatologists may have underestimated the temperature changes expected with global warming.
According to the UN's intergovernmental panel on climate change (IPCC) -- the consensus of the world's leading 2,000 climatologists -- the expected increase is up to 5?C over the next century.
But a recent conference of leading atmospheric scientists in Berlin concluded that the IPCC's models may have underestimated the cooling effect of atmospheric soot, the airborne industrial waste of the past. The upper limit of global warming, they suggested, should range between 7?C and 10?C, which would severely affect food and water supplies, traumatize most economies and fundamentally change everyday life.
The UN's World Meteorological Organization (WMO) warned last month that extreme weather events would become more frequent. On Tuesday Ken Davidson, director of the WMO's climate program, said: "The world is seeing a change in general conditions and in extremes. We are trying to understand if it's getting more frequent."