I find this EPA graph
Hmm... looks periodic.
I'm not saying there's not a warming trend right now. There does appear to be one. However, we can't get any conclusive evidence that it's caused by human factors (because no one was around 200-300 thousand years ago to make temperature measurements). As
far as anyone can tell, we could be in a natural warming trend. It's happened several times before.
What happens if we act on an "unprecedented global scale" and do something drastic to defeat global warming? What if it doesn't work? What would be the economic, social, and ecological impact of a failed attempt, even if the climate change
caused by humans? What if global warming is a natural phenomenon? Could our attempt to reverse a natural phenomenon have adverse consequences on the world's climate?