After deluge, expect more 'extreme rain It's essential we look at how this may impact our rainfall patterns over the next decade and beyond, so we can advise on the frequency of extreme weather in the future and the potential for more surface and river flooding. Four of the five wettest years since records began in 1910 have happened this century, and the long-term national average of annual rainfall has gone up by 2.1in (54mm), over the past 20 years. One likely cause is that a 1.26F (0.7C) increase in global air temperatures since pre-industrial times has led to a four per cent increase in moisture in the atmosphere, bringing with it a greater potential for heavy rain. Another possibility is that a change in sea surface temperatures caused by decreasing Arctic sea ice has brought about changes in weather patterns. Mike Childs, head of policy for Friends of the Earth, said: "Climate change is already having a major impact on Britain. So far the world has warmed by an average 0.7 degrees centigrade above pre-industrial levels - if temperatures rise by the four degrees scientists widely predict then we can only begin to imagine the impacts on our lives and livelihoods. He said it was "not too late" to act and claimed that greater energy efficiency and developing clean power from the wind, waves and sun could halt the greenhouse effect caused by burning fossil fuels. Ola Holmstrom, head of water at the engineering consultancy WSP, warned that infrastructure would have to be "completely rebuilt" in the most flood-prone areas to cope with future rainfall norms. Britain's average annual rainfall has been steadily increasing over the past 20 years, with the 30-year average rising from 43.3in (1,100mm) in 1961-1990 to 45.4in (1,154mm) in 1981-2010. Despite the trend towards warmer temperatures, last year was cooler than the average for the past 30 years, by 0.18F (0.1C), while the number of hours of sunshine was marginally down on the average. Britain was in drought for the first three months of 2012, following two drier than average years, but in April there was record rainfall, which continued for most of the year. Almost 8,000 homes and businesses were flooded and crops were ruined in many parts of the country. The picture varied widely across the UK, with 2012 being the wettest year in England, but only the 40th wettest in Northern Ireland, the 17th wettest in Scotland and the third wettest in Wales. The floods were made worse by a failure to clear water courses, said Owen Paterson, the Environment Secretary, and farmers blamed European Union red tape. Jim McClaren, of the National Farmers Union, said that farmers have to fill in a number of forms under the EU Water Directive before being allowed to clean out rivers. This can prove so time cosuming and expensive that many let mud build up. "European legislation is preventing farmers from using machines to clear rivers out," he said.