Oh Lordy, so many people repeating so many easily disproved chestnuts.
Global cooling was predicted in the 70's ! (It was a minor theory, without any real support.)
The climate has changed in the past. (Yeah, and water levels have fluctuated in the past. But if someone builds a dam downstream and my yard starts to flood, I'm not going to just shrug and call it a natural phenomena.)
And so on.
And then there was one guy who claimed that the role of CFCs in ozone depletion had been thoroughly debunked.