China has the highest number of such projects, which yield tradable carbon credits for investors in wind farms, solar power, small hydro, biomass or cleaning up planet-warming industrial gases.
The scheme, called the clean development mechanism (CDM), is part of the Kyoto Protocol climate pact and aims to help developing countries shift to low-carbon economies and also help rich nations offset their emissions by buying the carbon credits.
Each offset, called a certified emission reduction (CER), represents a tonne of greenhouse gas pollution saved from being emitted.
China now has 501 such projects registered, followed by India at 411 and Brazil with 156. Globally, the United Nations has approved 1,539.
Many of China's registered projects are in hydro and wind power, with others designed to capture methane from coal mines, landfills and agricultural waste.
Hundreds more Chinese projects are in the pipeline awaiting formal approval by the United Nations.
To date, approved Chinese CDM projects have been issued with 119,400,810 CERs, representing more than 40 percent of the total issued to date globally by the United Nations, but still a fraction of China's overall greenhouse gas emissions.