Any individual country implementing a carbon tax doesn't work because they put themselves at a big disadvantage, and goods and services go across country borders, taking with them almost-impossible to fairly calculate amounts of carbon.
The biggest things the world could do towards the "world dictator" approach would be:
* Have a consortium of countries implement a carbon tax, while taxing all inbound goods from countries that don't tax carbon.
* Adjust WTO rules to allow taxing imports based on estimated carbon content.
* Have the WTO decide which countries are "on track to meet carbon reduction targets". Allow taxes on imports from any country that isn't.
* Allow countries to "sue" another country for environmental damages. When they don't pay up, have a UN court able to threaten anything up to military action/takeover of the country's leadership to get payment.