What fossil fuel companies knew and when they knew it
The fundamentals of global warming have been well established for generations. Fossil fuel companies have almost certainly been aware of the underlying climate science for decades.
As early as 1977, representatives from major fossil fuel companies attended dozens of congressional hearings in which the contribution of carbon emissions to the greenhouse effect was discussed. By 1981 at least one company (Exxon) was already considering the climate implications of a large fossil fuel extraction project.
In 1988, the issue moved beyond the scientific community and onto the national stage.
Full article:The Climate Deception Dossiers (2015)