What David_G said. Global warming is a scientific issue. Maybe "what we lack is the will to change things" is the right analysis of the policy problems, but among climate change experts there's a whole lot more consensus about global warming than there is among AI researchers about the Singularity. "You can't say controversial things about global warming, but can say even more controversial things about AI" is a rule that makes about as much sense as "teach the controversy" about evolution.