Our ancestors already knew (or they should), but they wanted wealth.☠️
"… During the 1970s, scientific opinion increasingly favored the warming viewpoint. By the 1990s, as a result of improving fidelity of computer models and observational work confirming the Milankovitch theory of the ice ages, a consensus position formed: greenhouse gases were deeply involved in most climate changes and human caused emissions were bringing discernible global warming. …"
https://en.wikipedia.org/wiki/History_of_climate_change_science