Reuters: China, the world’s top greenhouse gas polluter, has passed a milestone in the number of U.N.-backed clean energy projects, with the world body approving more than 500 such schemes so far. 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 …