Not In Two Million Years Has CO2 Been This High
Professor Frank Aldrich lectured about rising atmospheric CO2 in my 1971 Climatology class. I recall a lecture on how climate would change if the north polar ice cap melted. None of us believed it would ever happen, but then we were students of physical geography, not human psychology. Now it seems so obvious that short-sighted and self-destructive use of excessive amounts of cheap dirty fuel to satisfy our personal ambitions was inevitable.
There are many good books and articles that have tracked the CO2 problem. Here’s a link to another one.