People affected by worsening storms, heatwaves and floods could soon be able to sue the oil and power companies they blame for global warming, a leading climate expert has said.

Myles Allen, a physicist at Oxford University, said a breakthrough that allows scientists to judge the role man-made climate change played in extreme weather events could see a rush to the courts over the next decade.

He said: "We are starting to get to the point that when an adverse weather event occurs we can quantify how much more likely it was made by human activity. And people adversely affected by climate change today are in a position to document and quantify their losses. This is going to be hugely important."

Allen's team has used the new technique to work out whether global warming worsened the UK floods in autumn 2000, which inundated 10,000 properties, disrupted power supplies and led to train services being cancelled, motorways closed and 11,000 people evacuated from their homes - at a total cost of £1bn.

He would not comment on the results before publication, but said people affected by floods could "potentially" use a positive finding to begin legal action.

The technique involves running two computer models to simulate the conditions that led to extreme weather events. One model includes human-caused emissions of greenhouse gases, the second assumes the industrial revolution never happened and that carbon levels in the atmosphere have not increased over the last century. Comparing the results pins down the impact of man-made global warming. "As the science has evolved this is now possible, it's just a question of computing power," he said.

Allen and his colleagues previously demonstrated that man-made warming at least doubled the risk of heatwaves such as the 2003 event that killed 27,000 people across Europe. No legal action resulted, but Allen said that was partly because most of the deaths were in France, where the legal system makes such cases difficult.

"We can work out whether climate change has loaded the dice and made extreme weather more likely. And once the risk is doubled, then lawyers get interested," he said.

Peter Roderick, director of the Climate Justice programme, said the most likely route for seeking damages would be tort cases, which deal with civil wrongs. Several have been attempted by US states against power and car companies only to be rejected by the courts.

Roderick said developing countries such as Nepal could also sue for compensation over damage caused by global warming. "As the issue of damages gets worse and worse, the chances of this happening will get greater and greater," he said. "I hope it happens."

Lawyers say it is only a matter of time before class actions are brought. However, Stephen Tromans, an environmental law barrister, said establishing causation would be one of the main difficulties. "It is one thing to be able to link levels of greenhouse gases with a specific event causing damage but, even assuming you can do that, quite another to establish causation against a particular company or industrial sector."

There are legal precedents for making exceptions to normal rules of causation. One example is the decision of the House of Lords on mesothelioma, where past employers can be liable for having contributed to the overall exposure, though the harm cannot be scientifically attributed to any specific period of employment.

"In that case an exception was made to the normal rules on causation in order to prevent an injustice that would otherwise have occurred," Tromans said.

There may also be grounds for a case on the basis that firms have tried to misinform the public - as in US cases against tobacco firms - about the effects of their business.

Owen Lomas, head of environmental law at City firm Allen & Overy, said: "If you look at the extent to which certain major companies in the US are accused of having funded disinformation to cast doubt on the link between man-made emissions and global warming, that could open the way to litigation."