It may appear that Exxon is against EU climate policy, or clean policy generally, but what it is actually suing for is rational global carbon pricing.
Massive oil companies love global carbon pricing… or carbon pricing in some form … because it allows them to assess whether future projects are possibly going to be viable …or not.
Windfall taxes with sunset clauses are by their nature less certain.
Most responsible corporations are already applying internal (shadow) carbon prices.
The EU has the biggest carbon market by traded volume and traded value.

