If dealing with coal impact, it's an accomplished fact (4,8)
I believe the answer is:
fait accompli
'accomplished fact' is the definition.
(synonyms)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for fait accompli that I've seen before include "Something already done (French)" , "Something already decided" , "Irreversible action" , "Irreversible act" , "A done deal" .)