The results suggest the threshold is close to the end of this century, and it could come sooner. The Arctic is already warming much faster than we thought it would. To think we're not going to get 4 to 5 degrees warmer in another 50 years is wishful thinking.
This is a real eye-opener set of results. The last time the Arctic was significantly warmer than the present day, the Greenland Ice Sheet melted back the equivalent of two to three meters of sea level.