it's funny how all the movies from the '70s and '80s (and even some from the '90s!) just assumed that smog would get worse and worse until the earth (or at least LA) was perpetually shrouded in smoke, then the government banned smog and it went away; incredible really.
Acid rain went from being a pollution disaster to an environmental success story. How did scientists manage to prove that acid rain existed,
similarly "acid rain" was a genuinely devastating problem that was solved, eventually, by banning it! turns out you can just do things.
I think the story of acid rain in particular is slightly less heartwarming than it is usually presented as, given that
(1) We didn't actually reduce SO₂ emissions in the 1980s, we moved them from America and Europe to Asia, reminiscent of how heavy industry in general moved that way. The BBC article notes in passing that the "problem persists" in China.
(2) When we finally reduced the emissions we noticed that, oops, both acid rain (SO₂ ) and smog (NOₓ) were actually load-bearing parts of ameliorating climate change. Now France is 43.8°C and we might have to start deliberately add SO₂ to the air to keep the planet livable...
I would say it's more like a TV show arc where we defeat the minor villains: dirty car exhaust, dirty coal exhaust, refrigerator outgassing, and we're congratulating ourselves until we hear CO2 laughing in the distance because although we're burning stuff much cleaner now we're still burning it! and all that carbon is ending up in the atmosphere and there's no quick fix for combustion that can stop it, no simple carbon capture system you can slap in the catalytic converter.
so we face the more fundamental challenge of transforming our energy architecture away from burning stuff towards solar and nuclear, which we kinda already knew we would have to do this entire time but it was expensive and inconvenient and people were getting rich the old way and in that sense you can see all the cleanups -- of genuine problems! -- as procrastination almost in the way they didn't solve the actual underlying issue, but it was easier for people to get mad about visible choking smog in the sky and dead lakes full of acid than an invisible change that might make the weather worse a century later.
The chart clearly shows an increase in SO_2 emissions in Asia slower than the decrease in Europe and North America, leading to a rapid decrease in total emissions, during a period of time where the world population was growing and the total economic output of the world, howeevr you want to measure it, was growing rapidly. It's hard to argue that the emissions were simply shifted from one region to the other. There is one brief period on the chart where total emissions increases because the rate of increase in Asia is so high. The x-axis doesn't have enough detail for me to tell if it's the 80s - I think it's later - but it's certainly not the period of greatest decrease in America and Europe so it doesn't make sense to say this represented a transfer to Asia unless the process of transferring emissions from America and Europe to Asia magically makes them disappear for a few years and then reappear with no economic disruption in the intervening years.
