You tell them that the sky is falling. You just tell them. Because it is falling. There is no larger game here. You tell them the truth. Plus you can't separate that decision from its relation to capital. There wasn't a situation where they couldn't tell the truth because capitalism did propaganda. They were part of the capitalist propaganda. The scientific consensus stuff was part of it. People were never given the chance to take it seriously. The real group that needed to change was the industrialists who were doing the most emissions. But they couldn't tell all the wealthy fucks to stop living their lives like kings, they had to sell a narrative that made them feel better about their choices. They lied to normal people in that process. What you're saying is that they had to lie to us because we couldn't handle it. We could and can if we had gotten the chance.

Also, we know that history doesn't change based on how educated or rational the public is. The public wasn't the largest emitter of CO2. The public didn't have any substantial political power. It's not that people were too irrational to handle it. It happened because the material conditions were that they had to tell the wealthy to stop being as wealthy.