Winter rainfall over northern England and Scotland will increase significantly both in frequency and intensity, they said in a report on the impact of global warming on Britain.
Severe winter gales will be more frequent and there will be an increased likelihood of high tides and flooding, but more hot, dry summers in the South will produce more droughts. The number of hot summer days will double by the middle of the century; by its end, there could be extremely hot summers like 1997 every other year, and very low summer rain in the South may be commonplace.
"These forecasts illustrate the very real threat that climate change poses to the United Kingdom," said Michael Meacher, the Environment minister, introducing the report from the UK Climate Impacts Programme, which is based on the latest predictions from the supercomputer model of the global climate at the Met Office's Hadley research centre in Bracknell, Berkshire.
The UK's average temperature is at present increasing by about 0.15C per decade, but the rate itself will increase and Britain is expected to be about 3C hotter on average at the end of the 21st century.
"That may not sound much," Mr Meacher said, "but it only needed a five- degree change in average temperatures to give us the last ice age. It is a very significant change."
The authors of the report, Dr Mike Hulme of the University of East Anglia and Dr Geoff Jenkins of the Hadley centre, stressed that the higher temperatures would not just mean hotter weather, but that existing weather patterns would be significantly disrupted, and gave rainfall as an example. "Manchester is going to get wetter," Dr Hulme said. "There will be more winter downpours in the North of England and Scotland. Will it be more miserable? If you don't like winter rain, it will be.
"On all of our scenarios winter precipitation increases substantially, by between 5 and 25 per cent. Daily rainfall intensities will increase - there will not just be more in a season, but individual daily rainfall storms will be more intense."
There would be three times as many days when an inch of rain fell in a given place, Dr Jenkins said. The higher rain in northern Britain was predicted by computer models of the climate not only in Britain, but also in the United States, Canada and Germany.
London's current average winter rainfall (in January, February and March) is 5.8in, while Manchester's is 7.9in, although it has had up to 18in sometimes. Glasgow's is 11.6in.
The heavier rain will combine with severer winter storms and the rise in sea levels, caused by global warming, to give a significantly higher risk of flooding, the scientists said. "The frequency of storm surges and high tides will increase much more substantially than at the moment," Dr Hulme said. An exceptionally high tide that now occurred, for example, at Harwich in Essex once in a hundred years would be likely once a decade, he said.
But the heavier rain in the North will be matched by much less rain in the South, where the summers will not only be hotter, but drier and more arid. "One of our most serious challenges will be how we manage water in the South and South-east of England," Dr Hulme said.
"We anticipate summers will become drier, by 5 to 10 per cent in the mean. These reductions in summer rainfall combined with increased evaporation from reservoirs are going to place much greater stress on water resources all over southern Britain."
The three-degree temperature rise predicted for 2100 was an average, he said. "Specific seasons or particular daily temperatures will change much more radically than that. For example, the very hot summer which we had in 1997 may occur every other year. Extremely low rainfall levels, which we might experience once or twice a century, might be occurring once or twice a decade.
"We no longer believe past weather records are an adequate guide to the future," Dr Hulme said.
In 10 days' time the Government will be publishing its long-awaited consultation paper on its strategy for countering climate change, and how it proposes to meet its target under last year's Kyoto treaty of cutting Britain's greenhouse gas emissions to 12.5 per cent below their 1990 level by 2010.
Mr Meacher said yesterday that the document would set out how each sector of society will have to deal with the problem, from industry and commerce to the public and government.Reuse content