Leading article: The floods have exerted a salutary effect

Few people in England or Wales will be surprised to learn that this summer has been the wettest of modern times. The Meteorological Office confirmed yesterday that more rain has fallen through May, June and July than over any comparable period since records began. Last month it was the North-east that bore the brunt, with extensive flooding in and around Sheffield and Hull. This month, thousands living in the Avon, Severn and Thames river valleys have been driven from their homes by the water after days of incessant rain. And this time last week, London ground to a halt after a deluge many likened to a monsoon.

News reports have been dominated by dramatic helicopter and boat rescues, scenes of high-streets transformed into waterways and cars and caravans swept away. Power to half a million homes was threatened, as the water rose around a Gloucestershire power station - and then, mercifully, subsided. But part of the county is dependent on bottled water and temporary tanks in the streets, after a treatment centre was flooded. The Army has been mobilised. Now there are warnings of the risk of disease.

None of this is the sort of thing we associate with our temperate islands. We have, of course, experienced the rage of nature in the past, but not so much, and not all at once. Our variable weather may be a perpetual national talking point, but variability came in moderation. We expect warm, wet winters, cool, dry summers and nothing too extreme. According to climate scientists at the Met Office, however, those times are over. Our expectations will have to change.

For Britain, global warming is likely to have two consequences, and both are starting to make themselves felt. On the one hand, winters will tend to be milder and wetter, while summers will be hotter and drier. This was the pattern we experienced two years ago, and to a lesser extent last year, when much of the South was afflicted by drought. On the other, the summer rain, when it comes, will tend to be sudden and heavy. We have to cater for a time when the deluges of the past few weeks will become more frequent. Drought and deluge are two sides of the same coin.

The flooding has been a traumatic and costly experience for many people, and its aftermath will be felt for months to come. Lives - though, thankfully, few - have been lost. The disruption in the flood-stricken areas has been enormous. Destructive and unpleasant the floods have certainly been; with hindsight, however, they may also be seen as exerting a salutary effect.

They serve to reinforce existing evidence for climate change and make it more difficult for sceptics to argue against it. The Met Office's scientists said yesterday that there was now clear evidence that man-made emissions of greenhouse gases were starting to change rainfall patterns in the climate zone that includes Britain. Having seen some of the consequences so close to home, it must be hoped that more people will be persuaded to reduce their carbon footprint - say, by giving up their 4x4s, patio-heaters and frequent flying - and put pressure on the Government to do likewise.

At the same time, the floods have demonstrated the inadequacy of much of our infrastructure, as more extreme conditions become the norm. The capacity of drains, the siting of power stations and treatment plants, the amount of low-lying land provisionally approved for development - all need to be reviewed. Clearly, too, arrangements for flood protection must be reconsidered. None of this will come cheap. But the political decisions should be less contentious now that the need for action has been demonstrated so conclusively: on flood protection and on climate change.