Post WWII did a few ok things for social policy, but didn't do much at all to reduce GHG emissions - except maybe China's one child policy and a more natural reduction in fertitlity in many other countries. but despite those , global population has still gone up 3-4x in that period.

Western world did begin to reduce coal usage but greedily replaced it with petroleum products. Lots of them also axed efficient public transport systems like intercity railways and local tram/streetcar systems in favour of inefficient but more convenient (up to the point of congestion) personal automobiles and quite staggering numbers (billions/trillions/fuckillions) of passenger km of aviation. I'm struggling to imagine a less efficient way to organise people and space that gave rise to that. Maybe we could have everyone live in Europe, work in Australia and go to USA for groceries.

Only major economic recessions like 2008 or covid actually cause emissions to fall in any material way - and they don't last close to long enough. Almost ever other clean tech thing of efficiency improvement is offset by increasing demand.

A few low density countries like Iceland and Norway were able to build enough hydro power to at least get clean electricity but , Norway? erm hardly anti-fossil fuel. Hydro is deemed impractical/inhumane in denser populated countries where they refuse to flood out all the valley dwellers.