The results from the world's biggest climate prediction experiment show that heat waves and floods could strike Britain this century. The experiment by the BBC and Oxford University began in February last year with a request for people to download a Grid computing program for climate prediction. About 200,000 people from across the world signed up and 50,000 have now run the program -- which plots the global climate from 1920 to 2080 -- long enough for the results to be statistically significant. Each program was slightly different, so that a very broad range of possible outcomes was covered. "People need to understand this is not a worst-case scenario. This is what we are increasingly confident will happen in the absence of substantial cuts in greenhouse gas emissions," said project coordinator Nick Faull of Oxford University. The initial results will be presented by renowned wildlife broadcaster David Attenborough in a BBC program -- Climate Change: Britain Under Threat -- on Sunday, giving snapshots of Britain in 2020, 2050 and 2080. They show flooding will become widespread and regular and that heat waves like the one which struck Europe in 2003 killing thousands of people will become the norm, making conditions in millions of homes and London's creaking underground system unbearable. "By using the computers of many tens of thousands of people around the world, all of whom will be affected by climate change in some way or another, we have created the largest "virtual" supercomputer dedicated to climate change that the world has ever seen," said Bob Spicer, chief academic for the program. "We have been able to do calculations that even on a normal supercomputer would have taken decades to complete," he added. Most scientists agree temperatures will rise by between 2 and 6 degrees Celsius this century, mainly because of carbon emissions from burning fossil fuels for power and transport, putting millions of lives at risk from flood and famine.