The record rainfall in Britain in the past three months is a foretaste of what is to come in a warmer world where the risks of flooding and drought will increase, scientists warned yesterday. More rain has fallen across England and Wales in May, June and July than in any comparable period since records began in 1766, Met Office scientists said. With July still yet to end, 15.26in (38.7cm) of rain has fallen in the past three months, making it the wettest May to July on record, surpassing the 13.8 in that fell in the same period in 1789. The Met Office said two extreme rainfall events occurred in these months which caused extensive flooding. One was at Fylingdales in North Yorkshire when 4in of rain fell in June, and the other was when 4.75in of rain fell on 20 July at Pershore College in Worcestershire.

Exceptionally heavy rain is likely to occur more often in a warmer world because air holds more moisture when it warms up, which can be released as a sudden downpour, said Peter Stott, a climate scientist at the Met Office. "The past is no longer a guide to the future. We no longer have a stationary climate," Dr Stott told journalists at the Science Media Centre in London. Computer models of the climate indicate that in a warmer world Britain will have drier, hotter summers and milder, wetter winters. However, they also indicate that when it does rain in summer, it will tend to result in heavier downpours, Dr Stott said.

"As the atmosphere warms up it can contain more moisture, so when it rains, it rains harder. The events we've observed could serve as a warning of the sort of events we'll see in the future." Dr Stott was part of a research team that found clear evidence that man-made emissions of greenhouse gases were influencing the global climate in a way that was changing rainfall patterns in the parts of the northern hemisphere that include Britain. The researchers said it was the first time that anyone had shown that human-induced climate change was causing a change in global precipitation - causing wetter-than normal conditions in latitudes above 50 degrees north, which includes much of northern Europe.

A "human fingerprint" on the global climate was detected by analysing weather records over the past century which indicate that global warming has resulted in more rainfall at high latitudes and lower rainfall in lower latitude regions - meaning that drier parts of Africa will be even drier. "This latest study cannot make the link between climate change and what we have experienced so far this summer. However, with a warmer climate there could be an increase in extreme rainfall events despite the expected general trend towards drier summers," Dr Stott said.

The immediate cause of this year's wet summer is the fact that the jet stream - a high altitude, westerly flow of air over the North Atlantic - has slipped further south than normal, bring successive bands of wet weather over Britain. Ewen McCallum, a forecaster at the Met Office, said the exceptionally hot weather in Mediterranean countries this summer was the flip-side to Britain's unusual weather conditions. "What goes up, goes down," Dr McCallum said.

More than twice as much rain has fallen over England and Wales in the past three months compared with the 30-year average. Dr McCallum said the weather was likely to remain unsettled for the next few days although there were indications that warmer, drier conditions were likely for southern England. "The broad signals are mixed at present. We need a dramatic change of weather patterns for any improvement," he said.
(By Steve Connor, The Independent, 27/07/2007)