Scientists say current concerns over a tipping point in the disappearance of Arctic sea ice may be misplaced.
Danish researchers analysed ancient pieces of driftwood in north Greenland which they say is an accurate way to measure the extent of ancient ice loss.
Writing in the journal Science, the team found evidence that ice levels were about 50% lower 5,000 years ago.
They say changes to wind systems can slow down the rate of melting.
They argue, therefore, that a tipping point under current scenarios is unlikely.
While modern observations by ship and by satellite give us a very accurate picture of the recent state of the ice, historic information is limited. The ice comes and goes without leaving a permanent record.
But a Danish team believes it has found an indirect method that gives a clear picture of the ice loss dating back 11,000 years.