How can you prove that expanding the mine actually caused any damages to the environment? With a chemical plant, if it leaks waste and poisons a nearby river, the damages are very real and easy to understand.

Expanding a mine that doesn't directly cause damages but increases CO2 doesn't have direct damages that you measure because it's global. Even with something like Fukushima, you can measure the damage it did to Japan, but what about all the radioactive waste it is leaking into the Pacific? How do you measure that catastrophe? Can you even prove that it has done any damage, even though it's obvious?