The Earth used to be much warmer. North America was divided into Laramidia and Appalachia with places like Texas and Nevada were entirely underwater. There used to be iguanas in Alaska. At that time, the late Cretaceous Period, there was no such thing as polar ice caps.
In 2011, we saw the main island in Japan, Honshu, move 8 feet in one day. For comparison, Honshu is about 15 percent larger than Washington State.
The point is that extreme changes to the Earth can happen quite suddenly. The theory that the Earth is warming and the ice might melt is not farfetched.
Scientists are worried CO2 concentration in the atmosphere can rise from the current 300 something ppm to 500 ppm.
The Cretaceous Period is believed to have CO2 at 1000 ppm. The Earth record for CO2 concentrations is 7000 ppm in the Precambrian era.
During the Cretaceous, era, the Earth appears to have been a very habitable place.
It would be very disruptive if all the ice melted but fears about this causing human extinction seem unwarranted.
Just noodling.