Scientists knew it was coming *decades* earlier than that, and it was even part of the popular consciousness too, but the fossil fuel industry has been fighting against that knowledge the entire time. Cooperative media, corrupt politicians and even religious zealots have helped them obscure the facts and muddy the waters about the issue.
I grew up hearing about human-caused global warming in the *1970s*. There was a great dystopian sci-fi movie that had climate change as one of its main plot drivers called
Soylent Green. It came out in 1973 and had big stars in it. Ordinary people were worried about it even back then.
It shows how successful the interests that stood to benefit from ignoring the problem have been. Even now, when it can no longer be ignored, we are still arguing about it. Before, they said it wouldn't happen. Now they say, even if it is happening, it wasn't caused by us.