England under water: scientists confirm global warming link to increased rain

It's official: the heavier rainfall in Britain is being caused by climate change, a major new scientific study will reveal this week, as the country reels from summer downpours of unprecedented ferocity.

More intense rainstorms across parts of the northern hemisphere are being generated by man-made global warming, the study has established for the first time ­ an effect which has long been predicted but never before proved.

The study's findings will be all the more dramatic for being disclosed as Britain struggles to recover from the phenomenal drenching of the past few days, during which more than a month's worth of rain fell in a few hours in some places, and floods forced thousands from their homes.

The "major rainfall event" of last Friday ­ fully predicted as such by the Met Office ­ has given the country a quite exceptional battering, with the Thames still rising. In Gloucester water levels had reached 34 feet, just 12 inches below flood defences ­ the same level as during the flood of 1947 ­ although a police spokesman said last night that the River Severn had stopped rising.
Meteorologists agree that the miserably wet British summer of 2007 has generally been caused by a southward shift towards Britain of the jetstream, the high-level airflow that brings depressions eastwards across the Atlantic. This is fairly normal. But debate is going on about whether climate change may be responsible for the intensity of the two freak rainfall episodes, which have caused flooding the like of which has never been seen in many places.

This is because the computer models used to predict the future course of global warming all show heavier rainfall, and indeed, "extreme rainfall events", as one of its principal consequences.

The new study, carried out jointly by several national climate research institutes using their supercomputer climate models, including the Hadley Centre of the UK Met Office, does not prove that any one event, including the rain of the past few days in Britain, is climate-change related.

But it certainly supports the idea, by showing that in recent decades rainfall has increased over several areas of the world, including the mid-latitudes of the northern hemisphere, and linking this directly, for the first time, to global warming caused by human emissions of greenhouse gases.

The study is being published in the journal Nature on Wednesday, and its details are under embargo and cannot be reported until then. But its main findings have caused a stir, and are being freely discussed by climate scientists in the Met Office, the Hadley Centre and the Department for Environment For Environment, Food and Rural Affairs.
One source familiar with the study's conclusions said: "What this does is establish for the first time that there is a distinct 'human fingerprint' in the changes in precipitation patterns ­ the increases in rainfall ­ observed in the northern hemisphere mid-latitudes, which includes Britain.

"That means, it is not just the climate's natural variability which has caused the increases, but there is a detectable human cause ­ climate change, caused by our greenhouse gas emissions. The 'human fingerprint' has been detected before in temperature rises, but never before in rainfall. So this is very significant.

"Some people would argue that you can't take a single event and pin that on climate change, but what happened in Britain last Friday fits quite easily with these conclusions. It does seem to have a certain resonance with what they're finding in this research."
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