Unfortunately, it seems like global warming causes damages that increase rather than decrease on the margin. That is, the aggregate economic damage of going from 1°C warming to 1.5°C warming is smaller than the damage of going from 1.5° to 2°.

This defies our normal intuition, whereby material objects can only become so broken. The 11th scratch on my car door is less important than the 10th because I already need to repaint the entire door.

Damages that increase on the margin also imply that it is more important, rather than less important, for countries to control their emissions if others are not doing so. The first tones of carbon dioxide removed from (or not added to) the atmosphere are the most important.