We’re witnessing the fastest decline in Arctic sea ice in at least 1,500 years

The Arctic Ocean once froze reliably every year. Those days are over. Arctic sea ice extent has been measured by satellites since the 1970s. And scientists can sample ice cores, permafrost records, and tree rings to make some assumptions about the sea ice extent going back 1,500 years.

Source: We’re witnessing the fastest decline in Arctic sea ice in at least 1,500 years