Early start of 20th century Arctic sea ice decline 

Arctic sea-ice has decreased rapidly during the last decades in concert with substantial global surface warming. Both have happened much faster than predicted by climate models, and observed Arctic warming is much stronger than the global average. Projections suggest that Arctic summer sea-ice may virtually disappear within the course of the next fifty or even thirty years.

Source: Early start of 20th century Arctic sea ice decline — ScienceDaily