Standards of evidence are obviously not what they used to be
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 towards 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 U.N. report due in 2014 about the impacts of climate change.
Experts have long blamed a build-up of greenhouse gas emissions for raising worldwide temperatures 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.