When did scientists first warn humanity about climate change?

"When did scientists first warn humanity about climate change?"

You've got to be kidding right? Our first scientists were shamans.(still are.....trial and error) Then priests. Our oldest communities sacrificed people and children to appease the weather gods. And avoid climate change.

Climate has been a racket since the beginning of man.
 
Our first scientists were shamans.(still are.....trial and error)

If you pick and choose quotes/ media coverage I agree, but looking at the overall consensus then they are not far wrong on predictions [if no action is taken].

I don't think anyone can deny the climate is changing with only the reasons to be disagreed on.