Hard I'd say- after the Great Depression and WW2, people wanted the nice life. Forget the Jimmy Stewart film, but released in about 1946 about helping others, bombed AIUI due in part to people tired for sacrifice. But for my (in)accurate guesses:
Cold War heats up faster, leading to maintaining that metals be recycled. Larger armies, and the knowledge of how pulling skilled workers out affects that industry, means nuclear gets a huge push in the 1950's (...somehow, and without killing people). This has the effect of less coal used (need those workers in the army), as well as cutting oil out of the electric generation business.
Let's throw in Spanish influenza Mark 2; maybe it will increase religious groups influence, so people are more willing to accept meatless Fridays, or church organized scrap metal collections. And since more people dead corresponds to less consumption, it helps lower pollution in an awkward way. The flu might even lead to the feared big recession after WW2 in the US; lets have a big Keynesian spending with pork to the cities to increase transit and rebuild/tear down the old housing, so people have less incentive to move to new suburbs with nice amenities.
Communist nations are hard- using the raw resources to grow your economy does work; it's just that in the 1970's on, Western (in terms of political leaning, not location) nations became more efficient. While the USSR GDP would increase, it was never as efficient as Germany, for example, in per ton of steel made. No idea how to correct that within communism. A detente breaks out late 1960's/70's, and the USSR bloc buys pollution equipment due to social unrest over acid rain? Do rain clouds flow from Russia to France? If we could recreate a bit the early 1990's issue between Canada and the US (US coal plants had bad impurities, forget what, goes in air, rains into Canada as acid rain, destroying statues and trees. Signed a treaty where the US would burn cleaner coal).
The unaligned nations might get aid to not just build armies and factories, but pollution control as well, if US (in particular) focused on what the needs of the poor in other nations was, and how to address that to stop communism. Thinking, the poor want jobs. Then, they want nicer jobs, maybe a small nice place to live, clean water. Would a foreign policy, say from the late 1950's on, be productive?
All of this is off the top of my head, so looking forward to corrections and new ideas from others! And a final idea, more doomsday, is that Israel almost falls, so launches all her nuclear weapons (so around 1968-on), hitting the almost all oil fields around there, the Aswan Dam (so the US either supports Israel or gets oil). F@cks up the global economy, of course. Any 30 Year style war or disaster in any nation that polluted highly in the past (don't have a graph to look at) would do the trick, but was going for more of a OTL but nicer try.