They probably know that visible effects of global warming won't manifest themselves until a century later: enough time for them and their kids. They don't care about their hypothetical grandkids. When the world starts collapsing in a century, they expect to have machines to fully replace 99% of the workforce: so most of the populace will fight for scare sources of clean water, while the rich would live somewhere in new Zealand, protected by unapproachable army of machines. That's what I think is their plan. However, I also think it's a naive plan.