B.4.1. There is high confidence that the probability of a sea ice-free Arctic Ocean during summer is substantially lower at global warming of 1.5C when compared to 2C. With 1.5C of global warming, one sea ice-free Arctic summer is projected per century. This likelihood is increased to at least one per decade with 2C global warming. Effects of a temperature overshoot are reversible for Arctic sea ice cover on decadal time scales (high confidence). 3.3.8, 3.4.4.7