The idea is good, but I think it's conclusions might be based on false assumptions. The modelling assumes that every country has two choices - "be part of climate club, and restrict carbon emissions", or "don't be part of the club, do whatever with carbon, but pay to export goods to club members".
That isn't the case. There is a third option: "Attempt to set up a different club with different rules".
When you model that, the smart move is to be a member of a club which is both big and inexpensive (ie. not many carbon restrictions). Over time, the stable position in this model is no action on anyone's part.
The stablest option of all is "no club". It will take a HUGE amount of interest and pressure and votes and money to create the first carbon club. Any set of countries attempting to create a competing "pollution club" will have to do it in opposition to that pressure. If that pressure isn't sufficient to prevent creation of the "pollution club" it probably wasn't sufficient to create the first "carbon club" in the first place.
That isn't the case. There is a third option: "Attempt to set up a different club with different rules".
When you model that, the smart move is to be a member of a club which is both big and inexpensive (ie. not many carbon restrictions). Over time, the stable position in this model is no action on anyone's part.