as this article from the New Yorker about carbon footprint shows.   There are some very unexpected results, e.g. it’s better from a CO₂  standpoint for a UK resident to buy roses from far-off Kenya rather than nearby Holland, or a New Yorker to drink wine from Bordeaux rather than Napa. 

And the moral of the story?   The most effective way ever found for dealing with pollution is to create a trading market.  It’s often politically unappealing because it feels like letting people “pay to be bad.”  But if there were a market in greenhouse gases, environmental groups would have a far easier path to leverage: instead of using their relatively paltry budgets to lobby–which often amounts to a winner-take-all game that they lose–every dollar used to buy up a ton of “right to pollute” reduces supply (and therefore raises the cost) of emitting greenhouse gases.   This would have exactly the effect they want: putting pressure on businesses to stop polluting, and rainforest nations to stop allowing their forest to be razed.   But it requires getting past the “moral” aspects of environmentalism and into realpolitik.