Let me just try to be helpful. I am not an economist, but I know how important it is, as are many of the other social sciences. So I have read a lot about it. I have read what the IPCC said in its fourth assessment on the costs. I have read what Nicholas Stern said in his report for the U.K. government. I have read what the World Bank said.
All of them seem to suggest that in the tackling of this issue, first of all, it will be more expensive if we don't tackle it; and secondly, the costs are manageable.
One estimate--it comes from the IPCC, which I'm simply reporting--is that if we adopted a target that was roughly maintaining the temperature below 2°C, then that would mean globally the GDP in 2050 would be what it would otherwise have been in 2049. In other words, we would have missed one year of global economic growth.