Shell already knew in 1988.

https://www.washingtonpost.com/news/energy-environment/wp/2018/04/05/documents-show-shell-foresaw-climate-change-three-decades-ago-and-knew-how-big-its-own-contribution-was/

Exxon scientists modeled and predicted global warming m between 1977 and 2003

https://en.wikipedia.org/wiki/ExxonMobil_climate_change_denial