This is ridiculous. People will just move towards the poles. Earth has been much warmer in the past and it was rainforests from pole to pole.
https://www.researchgate.net/figure/The-percentage-impacts-o... suggests it could be lot more than 1% too.
Lots of land in Canada and Siberia is going to become a lot more habitable.
"average elevation" is a bit of a strange metric for a continent.
Several large American cities are above 1600m and just looking at a map of the land below the ice of Antartica, there is plenty of low-lying land.
And we need not exaggerate the actual expected warming. The beyond-worst-case doomers don't need that much attention.
People are going to move away from coasts because the sea will make a new coastline. Agricultural zones will move north and around because of changes to weather patterns.
Pretty cold places will become less cold and new cities will pop up further north. Canada will do pretty well and grow a lot.
Perhaps- but it's also warming at twice the rate of the rest of the world, which makes adaptation even more challenging.