I first heard about carbon dioxide causing climate change in the late 1980s. I was dabbling in a bit of local politics with the Green party in Germany and preparing a manifesto for the 1990 elections, for which I wrote a couple of pages on emission control. The emissions we were worried about back then were, of course, toxic gases that caused visible problems on short timescales, such as acid rain and Waldsterben. I remember thinking something along the lines of "what's wrong with carbon dioxide? It's not even toxic!"
But with the first assessment report on climate change published in 1990 we soon learned what was wrong with carbon dioxide, and at that point the world really should have changed course and reduced emissions, but unfortunately they kept going up. As Naomi Klein has pointed out, it was an unfortunate coincidence that climate change only became apparent in the very moment when western democracies responded to the collapse of the communist bloc by abandoning all attempts to regulate corporations and markets, and these forces took the world in exactly the wrong direction.
Anyhow, 25 years after the problem was recognised and described, we're still making no progress towards solving it, which is very frustrating. I've comemorated and analysed this depressing anniversary in my latest feature which is out today in Current Biology:
Twenty-five years of climate change failure
Current Biology Volume 25, Issue 8, pR307–R310, 20 April 2015