Don't you think it is curious they would disregard mainstream science in placing the blame on humanity?
Who do you mean by "they"? Politicians? As in, why aren't they doing more to change things, despite the science?
I guess because it's difficult and expensive and unpopular. People don't want to give up their cars or meat.
And quite honestly if you've travelled to India or China (I pick those as they are two of the biggest polluters, partly because of their population) is is tempting to think we're screwed anyway and it doesn't matter what we do.
But climate change is a fact - I'm mid-40s and even in a timespan of 30+ years there's been a noticeable difference, yesterday it was almost T-shirt weather in London, that would have never happened in January in London when I was a kid.
And the scientists who know what they're talking about pretty much agree that we are causing it.