Scientists seek link between climate change and extreme weather events

In a radical departure from their previous position, scientists are to end their 20-year reluctance to link climate change with extreme weather – the heavy storms, floods and droughts which often fill news bulletins.

Climate researchers from Britain, the US and other parts of the world have formed an international alliance that aims to investigate exceptional weather events to see whether they can be attributable to global warming caused by greenhouse gas emissions.

They believe it is no longer plausible merely to claim that extreme weather is "consistent" with climate change. Instead, they intend to assess the probability that such conditions have been exacerbated, or even caused, by the global temperature increase seen over the past century.

The science of "climate attribution" is still in its early stages, so the move is likely to be pounced on by climate "sceptics" who question any link between industrial emissions of carbon dioxide and rises in global average temperatures.

In the past scientists have been extremely reluctant to link a single extreme weather event with climate change, arguing that the natural variability of the weather makes it virtually impossible to establish anything more than a general consistency between such events and what is expected from studies based on computer models. However, many climate scientists are now taking a more aggressive posture, arguing that the climate has already changed enough for it to be affecting the probability of an extreme weather event.

"We've certainly moved beyond the point of saying that we can't say anything about attributing extreme weather events to climate change," said Peter Stott, a leading climate scientist at the Met Office Hadley Centre in Exeter. "[There's] more moisture now in the atmosphere and the potential for stronger storms and heavier rainfall is clearly there."

Kevin Trenberth, a senior scientist at the US National Centre for Atmospheric Research (NCAR) in Boulder, Colorado, agrees about the need to emphasise the link between climate and weather. "The environment in which all storms form has changed owing to human activities; in particular it is warmer and more moist than it was 30 or 40 years ago," he said.