No mention of permafrost? Yes, the _air_ will be more habitable, but if the _ground_ is a boggy mess, you’re not going to be doing much with this newly habitable land.
There were also no occurrences of the words "sun", "light", or "insolation".
The further away from the equator you go, the more your sunlight becomes a fickle seasonal creature hitting you at odd angles in varying intensity. Temperature isn't the only variable affecting the growing season and agricultural productivity.
Detect it: poke a stick. It stops, at a pretty consistent depth, and not because of rock.
Remove it: overheat the planet. It will turn to mud. Anything built on it will subside or sink. Massive amounts of trapped organic matter will turn to methane.
Eventually, I presume the area would settle into a new climatic zone, with neither permafrost nor mud. Emphasis on "eventually".
The further away from the equator you go, the more your sunlight becomes a fickle seasonal creature hitting you at odd angles in varying intensity. Temperature isn't the only variable affecting the growing season and agricultural productivity.