Britain could be plunged into a 100-year-long winter within the next century, scientists have warned.
Ironically, the change would come about as a result of global warming cutting off the Gulf Stream which warms Britain's western shores.
Scientists say the change could happen relatively suddenly and may have already begun.
The Iceland Britain scenario is investigated on the Big Chill, broadcast on BBC 2's Horizon programme on Thursday night.
Expert Terry Joyce, from Woods Hole Oceanographic Institute in the US said he put the likelihood of an abrupt plunge in British temperatures within the next 100 years at 50%.
He said: "It will be quick, and suddenly one decade we're warm, and the next decade we're in the coldest winter we've experienced in the last 100 years, but we're in it for 100 years."
Global warming threatens the gulf stream because it is predicted to produce more fresh water, which would dilute the salty waters of the current.
This, in turn, would stop it sinking, and if this happened the heat it carries would be cut off.
Dr Bill Turrell, from the Fisheries Research Service in Aberdeen, has been measuring the salt content of the Gulf Stream current flowing north of Scotland.
Dr Turrell's measurements show that the Gulf Stream's salinity is indeed dropping.
He said: "We were really worried when we saw these results. We'd never seen a change like this before.
"These changes are fundamental; they are substantial; They are going to impact our climate and the climate our children have to live in."
Ironically, the change would come about as a result of global warming cutting off the Gulf Stream which warms Britain's western shores.
Scientists say the change could happen relatively suddenly and may have already begun.
The Iceland Britain scenario is investigated on the Big Chill, broadcast on BBC 2's Horizon programme on Thursday night.
Expert Terry Joyce, from Woods Hole Oceanographic Institute in the US said he put the likelihood of an abrupt plunge in British temperatures within the next 100 years at 50%.
He said: "It will be quick, and suddenly one decade we're warm, and the next decade we're in the coldest winter we've experienced in the last 100 years, but we're in it for 100 years."
Global warming threatens the gulf stream because it is predicted to produce more fresh water, which would dilute the salty waters of the current.
This, in turn, would stop it sinking, and if this happened the heat it carries would be cut off.
Dr Bill Turrell, from the Fisheries Research Service in Aberdeen, has been measuring the salt content of the Gulf Stream current flowing north of Scotland.
Dr Turrell's measurements show that the Gulf Stream's salinity is indeed dropping.
He said: "We were really worried when we saw these results. We'd never seen a change like this before.
"These changes are fundamental; they are substantial; They are going to impact our climate and the climate our children have to live in."
