I've been to China multiple times and I find the Arctic Circle very appealing as a life experience / novelty / adventure but I would still choose two years in China over one in the arctic.
It would be (presumably) a good career move, an excellent cultural experience, more time away, more exposure to mandarin = quicker and easier to learn, you'd get to see what a real modern country is like and possibly form connections or even friendships with people who might be in a position to work on projects with real positive impact.
Over the span of two years you'd have a few days here and there that you'd need to occupy and China has lots of distinct unique places and cultures, and of course the variety of climates / biomes.
Also what you said about China taking climate change seriously is representative of I think the biggest appeal for me, which would be the mental relief I'd get living somewhere that takes things seriously, is serious about solving problems and that has a proper healthy respect for science and reason. At a policy level anyway-
A friend of mine taught there for a bit over a decade and is a lot less prone to romanticizing everything. In day to day life China isn't an especially rational and efficient place, not tryna sound naive and utopian. But on the whole they are pushing consistently in the right direction on policy and implementation, and for me that would be very subconsciously comforting thing.
Like how libs get to feel when brunch isn't cancelled. I want that. I want communist brunch and I want it for you too.
But the Arctic Circle option would be fucking cool too, what an awesome decision to have to make. 