This only factors in economic damage from the higher temperature. It's not looking at floods, extreme weather, and definitely not looking at second-order effects - mass migrations, increased risk of war etc.
It is an absurd fantasy to imagine that the only effects of global warming in the next hundred years will be economic contraction (though note that economic contraction YoY itself is almost unheard of in the US and Europe, and will bring dire consequences).
It's also an absurd fantasy that you can predict the future in technological advancements on a 100-year scale either. Not to mention the intractibility of climate modeling over that time period.
Considering a few years ago people were worried about the problems of jobs being automated away, you might imagine a little climate change creating extra work for people would be good for social cohesion.
But it's all just a bunch of bozos with PhD's and masters degrees.
TL;DR: Asssumming one can translate different lattitudes' GDPs to that of a planet undergone global climate disruption is ... an exceedingly dubious proposition.
It is an absurd fantasy to imagine that the only effects of global warming in the next hundred years will be economic contraction (though note that economic contraction YoY itself is almost unheard of in the US and Europe, and will bring dire consequences).