Atmospheric rivers caused the UK's worst floods

YOU may not even know they are there, but their impact is immense: huge atmospheric rivers that wind their way through the skies have been linked to the 10 largest winter floods in the UK since the 1970s. A study of similar systems in California suggests that such floods could become more frequent and severe if greenhouse gas emissions accelerate.

Atmospheric rivers (ARs) are giant ribbons of moist air, at least 2000 kilometres long and several hundred kilometres across, which move water across the mid-latitudes. They flow in the lower troposphere, where winds with speeds in excess of 12.5 metres per second can carry as much water as the Amazon river. At any given time, four or five ARs carry nearly 90 per cent of the moisture that is moving towards the poles.