During any period of extreme cold, you can bet someone will point to the wintry conditions outside and say 'So much for global warming, eh?'

But this nugget of saloon bar wisdom fails to differentiate between weather, the day-to-day condition of the atmosphere, including temperature, rainfall and wind; and climate, the average weather conditions of a place, measured over a longer period of time, typically 30 years.

Dr Tim Osborn, a reader in climate science at the Climatic Research Unit of the University of East Anglia, said atmospheric circulation this winter had been very unusual.

'When you get cold air moving down from the Arctic, air from somewhere else is moving to the Arctic. In recent weeks Greenland has been very warm while we have been very cold.

'Global warming is not just moving heat around; it's increasing the heat content of the atmosphere.

'Last winter was extremely snowy and pretty cold here, but when you take the measurements from weather stations across the world it was one of the top five warmest. Someone in the UK would never have thought that but it was exceptionally warm in northern Canada, parts of Asia and north Africa.'

Dr Osborn said that climate records for England dated back to 1659, and that while last winter may have seemed quite extreme to us, there were 56 colder winters on record.

'Climate is the average weather over a 30-year period. Compared to other 30-year periods, the current one is the warmest of those, but there are lots of year-to-year fluctuations,' he said.