I am aware that this is not a realistic course of action. The problem is that scaling down fossil fuel production is going to be a very bad economic decision for any country in the short term, and it seems to be difficult, politically, to take that local economic hit for the long term interests of humanity at a global scale. At least the immediate threat of nuclear repercussions would convert the alternative into a short term local risk, which is politically more palatable.

Of course, any nuclear nation threatening other nations like that would become a pariah, so it isn't likely to happen. Also because, as you say, it is against their own short-term economic interests.

Edit: It would be pretty ironic if North Korea, which is already a pariah, turned out to save the planet by taking on that role.