Ryan Avent is, as usual, spot on:
were climate change to involve a cost of 3% of GDP spread evenly (or even progressively!) across the world’s population, then perhaps we could live with that. Unfortunately, it will not be spread evenly. There is an excellent chance that those most responsible for climate change will suffer the least, in fact, while the brunt of the pain is felt by the poor. If we have a moral obligation not to invade Bangladesh, kill thousands of its citizens, and create millions of permanent refugees, then it’s safe to say we have a moral obligation to take reasonable and affordable steps to prevent a climate catastrophe in Bangladesh for which we bear heavy responsibility.
I honestly don’t understand why so many people who profess to give a damn about people in poor countries seem not to when it comes to global warming. Maybe it’s because they realise that doing something about global warming will involve unpleasant sacrifices or policy responses they’re uncomfortable with. Do they think the rest of us are happy about global warming or something? I would dearly love to be able to fly around the world to my heart’s content, for example, but I know the real cost is too high, so I feel I have to sacrifice some flying. That pisses me off, to be honest, but then there are these things called trade-offs in life.