Global warming behind the UK's winter rainstorms?

Flooding in the UK last winter may have been partly caused by man-made climate change, a group of scientists will assert this week. Their claim is that emissions of greenhouse gases have increased the risks of extreme wet winters by a factor of 25% and that this could be a cause of last winter's rainstorms.

Their findings are to be fully unveiled at the American Geophysical Union conference in San Francisco. The finding result from a joint project between Oxford University and the UK Meteorological Office.

The Met Office ran 40,000 computer simulations of weather conditions in the run up to last winter. Half of the simulations included climate-change related data, in the form of observed temperature rises. The remainder excluded them. The latter group indicated significantly less rainfall.

In an summary of the project's findings Professor Peter Stott, head of the Met Office's climate monitoring and attribution team, says, "First results show that anthropogenic [caused by humans] climate change led to a small but significant increase in the fractional attributable risk for 30-day peak flows for the River Thames."

Oxford University's Nathalie Schaler led the research project. She is careful to not overplay the results. "It is not possible to say that any specific flood was caused solely by human-induced climate change," she says. "But we have shown that the odds of getting extremely wet winters are increasing due to climate change."

The findings reflect a growing consensus among scientists that climate change is impacting directly on weather conditions, particularly with regards to extreme events including floods.

Increasing levels of carbon dioxide in the atmosphere mean that more heat is retained. This boosts evaporation from the oceans and leads to additional rainfall.

Meanwhile, United Nations talks on climate change ended yesterday in Peru. A plan was agreed for cutting greenhouse gas emissions, though it has been heavily criticised by environmental campaigners for being too limited in scope. Further talks are due next year in Paris.