There is a novel about this very thing called Ministry For the Future. In the book, the UN agency formed to enforce the Paris agreement has no teeth. It takes

There is a novel about this very thing called Ministry For the Future. In the book, the UN agency formed to enforce the Paris agreement has no teeth. It takes some high-profile climate disasters to get some countries to pay attention, and some eco-terrorism to get corporations/one-percenters to pay attention. Only after that does the agency get any real power to set standards and hold anyone to them. It’s a broadly optimistic novel despite all that. I’m less sanguine about the outcome in the real world, but I fully expect some of the same tragedies (massive heat waves that kill maybe millions) and terrorism (drone swarms bringing down airliners/private jets) to occur.