The Clean Development Mechanism (CDM) helps rich countries cut their pollution by investing in clean projects in poorer countries. It's part of the effort to reduce global warming. Most of the pollution cuts come from clean energy and cutting other gases. Many projects are in China, India, Brazil, and Mexico. But some say the CDM didn't help enough, and some problems have led to a drop in prices for the pollution cuts. The CDM ended in 2022, but it's still running until the new rules from the Paris Agreement start.