Hot summers to become commonplace in Europe

Blistering hot summers similar to the one of 2003 when thousands of Europeans died of heat-stroke will become commonplace because of climate change, a study has found.

Scientists estimate that global warming has already at least doubled the risk of similar hot summers and that if the climate continues to change such summers will occur once every couple of years. It is estimated that between 22,000 and 35,000 people died of heat-related deaths in Europe during the summer of 2003 when soaring temperatures and prolonged drought also caused widespread forest fires and crop failures in the Mediterranean.

Until now it has not been possible to say with any accuracy how much of this extra heat was the result of man-made global warming and how much of it simply the result of a naturally warm summer.

Peter Stott of the Met Office's Hadley Centre and Daithi Stone and Myles Allen of Oxford University have, however, found a way of teasing apart the human and natural influences on the record temperatures measured across Europe last year.

Using a computer model of the climate, they found the extra heat that made the summer of 2003 the hottest for a least 500 years was largely the result of human influences on the climate, such as the burning of fossil fuel which exacerbates the planet's greenhouse effect.

"We simulated 2003 summer temperatures over Europe, with and without the effect of man's activities, and compared these with observations," said Dr Stott.

"We found that, although the high temperature experienced in 2003 was not impossible in a climate unaltered by man, it is very likely that greenhouse gases have at least doubled the risk.

"Our best estimate is that such a heatwave is now four times more likely as a result of human influence on climate," he said.

The study, published in the journal Nature, calculates that human influence is to blame for 75 per cent of the increased risk of such a heatwave occurring.

At the current rate at which the climate is changing, the scientists estimate that by the 2040s more than half of the summers will be warmer than that of 2003, and by the end of the century a summer similar to 2003 will be classed as unusually cold.

"Anthropogenic [man-made] warming trends in Europe imply an increased probability of very hot summers," the scientists write.

"Nevertheless, it seem likely that past human influence has more than doubled the risk of European mean summer temperatures as hot as 2003," they continue.

"And with the likelihood of such events projected to increase 100-fold over the next four decades, it is difficult to avoid the conclusion that potentially dangerous anthropogenic interference in the climate system is already underway."

Lawyers wishing to pin blame on organisations or governments for exacerbating global warming may use such scientific analysis as evidence in a court of law, said Dr Allen, who has co-authored a study into the legal implications of such research with Richard Lord, QC.

"Quantifying the costs of climate change requires being able to separate natural from man-made contributions to weather risk," Dr Stott said.

"If a dice is loaded to come up six and does so, then clearly there is a sense in which the loading helped this to happen.

"But when several sixes turn up, it makes no sense to ask which of these are due to the loading. In the same way, we cannot say which of the heatwaves were man-made and which were natural, but we can apportion blame for the change in risk," he said.

The day may soon come when Californian farmers sue EU member states for authorising emissions of greenhouse gases that threaten the farmers' water supplies, say Stott and Lloyd.

"Whatever the weather in Europe next summer, we can be sure that the argument over who pays for the cost of climate change is here to stay," they say.

Doug Parr of Greenpeace said: "This study could be a stepping stone to holding climate villains to account. Like the tobacco industry, big polluters could face massive lawsuits. Polluters should know that if they ignore moral arguments for action, legal liability could hit them."

- INDEPENDENT