Myles Allen, a physicist at Oxford University, 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 has developed a technique which involves running two computer models to simulate the conditions that led to extreme weather events. One model includes human-caused emissions of greenhouse gases, and the second assumes the industrial revolution never happened and that carbon levels in the atmosphere have not increased over the last century.
"As the science has evolved this is now possible, it's just a question of computing power," he told the Guardian.
Prof Allen's team used the new technique to assess whether global warming worsened the UK floods in autumn 2000, which affected 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.
Although he would not comment on the results before publication, he said people affected by floods could "potentially" use a positive finding to begin legal action.
Prof 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. However no legal action resulted from their findings but the researchers said this was partly because most of the deaths were in France, where the legal system makes such cases difficult.
Several cases been tried by US states unsuccessfully but lawyers say it is only a matter before class actions are brought. But environmental law barristers say establishing "causation" or the relationship between conduct and result would be one of the main difficulties.