Climate deniers say that climate change is a hoax because they heard that acid rain was a problem and nothing ever came of it.

We literally had a major government program to fix the problem!

https://www.epa.gov/acidrain/acid-rain-program

Acid Rain Program | US EPA

View an overview of the Acid Rain Program, including information on the program's SO2 and NOx reductions.

US EPA

@davidho

Same deal with Ozone hole.

The problem was growing, but international effort changed the spray can propellant from CFCs to less nasty gases.