James Hansen’s colleague in 1988 was Syukuro Manabe – legendary early climate modeler.
Here he explains now well-observed arctic warming due to “polar amplification” – understood from basic physics, and now very well observed.
See below, NASA’s animation of global temperature changes makes arctic warming clear from 1881 to 2016.
I gotta remember Manabe’s name. For so long I have referred to him as “that smart Japanese guy”.