We did know in the 20s. We knew in the 30s. We knew in the 40s. We absolutely knew in the 50s (oil industry funded their own studies on this). We knew before we decided to direct billions into a federal interstate highway system that bulldozed countless communities of color and killed many cities' downtowns and sense of connectedness.

I don't see anything positive about being forced to participate in this car-ownership game where 99% of North American cities are designed around car ownership, and if you don't own a car you're screwed. I don't WANT to own a car, I don't want to direct countless thousands of dollars to a car note, car maintenance, gas, etc. I want the freedom to exist without needing to own an absurdly expensive vehicle to get myself around. There's nothing freeing or positive about that unless all you've ever known and all you can imagine is a world in which cities are designed around cars and not people.

It was pretty well established scientifically in 1900 that increasing atmospheric CO2 would result in increasing global temperature, but I don't think it was really in the public awareness for many decades. "Global warming" wasn't coined until the '70s.