Climate change will bring greater extremes in weather, the Government's outgoing chief scientific adviser has warned as he called for urgent action to tackle global warming.
Professor Sir John Beddington said the effects of climate change on the weather were already being felt in the UK.
"In a sense we have moved from the idea of global warming to the idea of climate change, and that is rather important - yes, indeed, temperatures are increasing but the thing that is going to happen is that we are going to see much more variability in our weather," he told BBC Breakfast.
"I think you only have to look at the last few years to see how that is actually starting to manifest itself even in the UK."
Sir John said there were "massive problems" in the world of food, water and energy security as the global population increases, all of which would be exacerbated by climate change.
Even if effective action was taken now on global warming, he said there would be "significant" climate change over the next 20 to 25 years as results of past global emissions.
"We have massive problems in the world - in 12 years' time there will be another billion people on the planet and we have big issues of food security, water security and energy security and many, many people will start to be living in cities," he said.
"These are massive problems; climate change is just going to make it worse."
He said there were some "uncertainties" in the analysis of climate and climate change.
"But those uncertainties are completely outweighed by the enormous body of evidence that shows it is happening and is happening in the sort of ways climate models would expect," he said.
"For example the Arctic is heating up vastly faster than other parts of the world - this is exactly what the climate scientists are predicting."
Sir John's remarks were made as Britain experienced freezing cold weather and snow, with thousands of homes across the UK without power and many roads still impassable.
Almost 8,000 homes and businesses were flooded in 2012, as the UK was battered by repeated heavy rain, storms and floods.
England and Wales experienced 10 separate flooding events between April and December last year after widespread drought gave way to the wettest summer in a century, with unusually high rainfall totals and river levels around the country.
Sir Mark Walport, currently director of the Wellcome Trust, takes over as the Government's chief scientific adviser on April 1.