SCIENTISTS are finding evidence that man-made climate change has raised the risks of individual weather events, such as floods or heatwaves, marking a big step toward pinpointing local costs and ways to adapt to freak conditions.
"We're seeing a great deal of progress in attributing a human fingerprint to the probability of particular events or series of events," said Christopher Field, co-chairman of a UN report due in 2014 about the impacts of climate change.
Experts have long blamed a buildup of greenhouse gas emissions for raising worldwide bodyeratures and causing desertification, floods, droughts, heatwaves, more powerful storms and rising sea levels. But until recently they have said that naturally very hot, wet, cold, dry or windy weather might explain any single extreme event, like the current drought in the United States or a rare melt of ice in Greenland in July. But for some extremes, that is now changing.
A study this month, for instance, showed that greenhouse gas emissions had raised the chances of the severe heatwave in Texas in 2011 and unusual heat in Britain in late 2011. Other studies of extremes are under way.
Growing evidence that the dice are loaded toward ever more severe local weather may make it easier for experts to explain global warming to the public, pin down costs and guide investments in everything from roads to flood defenses.
"One of the ironies of climate change is that we have more papers published on the costs of climate change in 2100 than we have published on the costs today. I think that is ridiculous," said Myles Allen, head of climate research at Oxford University's Environmental Change Institute.
"We can't (work out current costs) without being able to make the link to extreme weather," he said. "And once you've worked out how much it costs that raises the question of who is going to pay."
Industrialized nations agree they should take the lead in cutting emissions since they have burnt fossil fuels, which release greenhouse gases, since the Industrial Revolution. But they oppose the idea of liability for damage.
Almost 200 nations have agreed to work out a new deal by the end of 2015 to combat climate change, after repeated setbacks. China, the United States and India are now the top national emitters of greenhouse gases. Field, Professor of Biology and Environmental Earth System Science at the University of Stanford, said that the goal was to carry out studies of extreme weather events almost immediately after they happen, helping expose the risks.
"Everyarticlebody who needs to make decisions about the future - things like building codes, infrastructure planning, insurance — can take advantage of the fact that the risks are changing but we have a lot of influence over what those risks are."
Another report last year indicated that floods 12 years ago in Britain — among the countries most easily studied because of it has long records — were made more likely by warming. And climate shifts also reduced the risks of flooding in 2001.