The precautionary principle is attractive, but it ignores the possibility that lost opportunity costs can exceed those of the risk being avoided. Turning on the lhc was considered by some to have a miniscule risk of turning earth into a tiny black hole that would last a moment before evaporating. My particle physics friends laughed and agreed there was a non zero risk. The notion that an action with a tiny yet finite risk of an event with infinite cost should itself have infinite cost would preclude most everyday activities. Not that climate change or emissions fit that category I think the risks aren't that small, just saying be careful with the precautionary principle.

Some amount of climate change would probably be beneficial to some nations. Russia would vome to mind with more arable land potentially becoming available, but some models show it being borderline too dry to grow on. Those same models show a net benefit to agriculture in Midwestern US. I wonder if xkcd or 538 could whip us up a map of climate change winner/losers and areas that support co2 policies?