* All countries to agree on an incentive scheme (unlikely - although big trading blocs like EU/China/Russia/USA might be able to bully the rest of the world into it with the threat of sanctions if they do not agree)

* Some countries to agree on a scheme, and to break WTO rules to penalize (carbon tax) imports and subsidize exports to/from those who do not.

Or... the world continues on the current trajectory of decarbonizing highly visible things only (Electric cars, solar panels on the roof!) to appease voters while avoiding decarbonizing anything that much affects nationwide competitiveness (eg. steel/fertilizer production).