It costs money to monitor. But frankly, for the amounts involved [1], there's no reason Montreal or Paris shouldn't have included monitoring and paid for it by

It costs money to monitor. But frankly, for the amounts involved [1], there's no reason Montreal or Paris shouldn't have included monitoring and paid for it by penalties on violators. Edit: After reading some summaries of Montreal compliance, it seems the general thinking is (a) it would be too hard to get agreement on monitoring & penalties in the initial draft & (b) self reported monitoring, in cooperation with UN agencies, tallied against general atmospheric measurements would reveal major discrepancies. Not sure how this one slipped through the cracks. [1] E.g. USD$10M/yr for NASA carbon monitoring research http://www.sciencemag.org/news/2018/05/trump-white-house-quietly-cancels-nasa-research-verifying-greenhouse-gas-cuts http://www.sciencemag.org/news/2018/05/trump-white-house-qui...