I recall my father, who was a marine biologist and biochemist, talking about climatic shifts caused by greenhouse gasses such as CO2 being a future problem when I was only about ten or eleven, so it was certainly a suspected problem even back in the early seventies. He followed the literature on it quite closely for a long time.

There are also SF stories based on the concept going back to the sixties at least.

Global warming via manmade CO2 emissions certainly isn't a new idea. I can well believe that people in the industries that tended to contribute to such emissions were well aware of the problems for a very long time. As always, though, the profit motive tends to push common sense and cautious approaches out of the way fairly easily