If we "knew" this would happen decades ago then you can't blame for favorite whipping boy. 
If we "knew" this would happen decades ago, & we didn't care, it was because of greed which drives people to do stupid things like building on flood plains or ontop of a earthquake fault. 
The Ice Age was what climate change looked like thousands of years ago. 
I think the Dust Bowl of the 1920's was a look at climate change then. 
How about the droughts that are plaguing the Southwest and parts of California?
There is a story told by Southeast tribes about the "great flood" that occurred here in Southeast. How some survived and others did not. Have you ever found fossils of sea shells and sea creatures on top of a mountain ? 
Are people contributing to climate change ? Sure they are!  But not to the extent that you credit them with. 
Just as the FACT that a huge killer earthquake will hit the West Coast, including parts of Alaska and British Columbia and tidal waves will follow, are we ready?