Ozone hole over Antarctica.
It is possible for us to work together and fix these things.
Edit:
Moving away from leaded gas might be another example.
(CFCs and leaded gas invented by the same dude, fun fact: https://en.wikipedia.org/wiki/Thomas_Midgley_Jr. Quite a legacy...)
When the costs are low and require no change in personal behaviour, nor even belief in the problem. Billions of people had no idea about changes to aerosol propellants or refrigerants and they were not required to know or agree in order to solve the problem.
Do people have to know about what generates their electricity? They get input now, but we could probably just stop taking public input on new infrastructure and that would avoid poorly motivated protests of wind farms or nuclear.
They do not need to know what generates there electricity but...
- when what generates the power changes the landscape they can see, many people get upset, however irrationally
- many people are emotionally attached to lifestyle objects that use fossil fuels, i.e. cars, boats, planes, etc
- even where there are good options, most people are not willing to spend one extra penny
- even when there are options that cost less (i.e. bicycles, walking) humans spend a lot of their energy thinking about status and struggle to voluntarily choose things that they fear might result in a loss of status
- even if you solve all that, collective action problems are a named thing for a reason - they are hard and don't necessarily have obvious answers.
My point is not that everything is hopeless, but that OP who said "Have we ever as a species successfully changed our behavior on a scale..." has a point that we will have to grapple with if we want to actually change stuff. Wishing human nature away doesn't actually solve anything.
Stop taking public input on public infrastructure. That would go over life a lead balloon.
Good point - maybe also stop taking public input on decisions. :V
I kid, but I get more sympathetic to totalitarian countries seeing how people react to some things too. it simplifies "banding together" if there's fewer decision makers I guess and I can't think of a good way to have that squared with democracy.
You also get no feedback from people, massive corruption and many useless megaprojects end up being built at the cost of everything else (because everyoneis too afraid to point out its nonsense & regime adjacent thugs will then make it 5x as expensive and pocket the extra money).
We haven't fixed the ozone hole yet. It'll take another 40 years for it to return to the levels prior to 1980:
https://science.nasa.gov/earth/earth-observatory/ozone-hole-...