  The downward trend in the amount of Arctic sea ice has a wide range of
environmental and economic consequences including important effects on the pace
and intensity of global climate change. Based on several decades of satellite
data, we provide statistical forecasts of Arctic sea ice extent during the rest
of this century. The best fitting statistical model indicates that overall sea
ice coverage is declining at an increasing rate. By contrast, average
projections from the CMIP5 global climate models foresee a gradual slowing of
Arctic sea ice loss even in scenarios with high carbon emissions. Our
long-range statistical projections also deliver probability assessments of the
timing of an ice-free Arctic. These results indicate almost a 60 percent chance
of an effectively ice-free Arctic Ocean sometime during the 2030s -- much
earlier than the average projection from the global climate models.
