The book looks interesting, I added it to my cart for my next monthly book buy.

In terms of Summer Sea Ice in the Arctic, it's OVER at this point.

At +2°C there will be no summer ice cap on the Arctic Ocean. We are on track to get there between 2030-2035.

Arctic Amplification makes that +8°C in the High Arctic.

The official term is "Blue Ocean Event" or BOE. However it's not a binary switch, we are already in the run up to a BOE in the early 30's.

As the ice vanishes a LOT more ENERGY goes into the water during the Summer. In the Fall that inhibits the growth of new ice AND pours HEAT into the polar atmosphere. Warming the air and reducing the thermal gradient between the pole and the lower latitudes.

The energy bleed from the water continues until the surface air becomes cold enough for a crust if new ice to form. Which then locks the remaining HEAT in the water up until the Spring. When it will contribute to even earlier melting of the winter ice.

It's a feedback that is projected to cause an additional +0.5°C of warming.