In case you missed it, this was one of three excellent articles Nick Davies did for The Guardian a few weeks ago.
...The CDM is one of two global markets which have been set up in the wake of the Kyoto climate summit in 1997. Both finally started work in January 2005. Although both were launched with the claim that they would reduce greenhouse gases in the atmosphere, evidence collected by the Guardian suggests that thus far, both markets have earned fortunes for speculators and for some of the companies which produce most greenhouse gases and yet, through a combination of teething troubles and multiple forms of malpractice and possibly fraud, they have delivered little or no benefit for the environment.
...There are doubts about the validity of some of these CERs, on two separate grounds. First, some of them appear to breach the CDM's requirements for sustainable development - 53% of the existing CERs come from just six monster projects, in India, China and South Korea, all of which engage in the most controversial form of carbon reduction. They manufacture refrigerant which produces as a side effect a gas called HFC-23. Although carbon dioxide is the most common greenhouse gas, HFC-23 is 11,700 times more likely than carbon dioxide to encourage global warming. Refrigerant companies find it relatively cheap to install an incinerator to burn the HFC-23 and, once that is converted into certified reductions of emission, each tonne saved can be sold as 11,700 carbon credits. These companies are now earning millions of euros from these credits - more than from selling their refrigerant products.
June 2, 2007: Source
June 2, 2007: Abuse and Incompetence in Fight Against Global Warming
June 16, 2007: The Inconvenient Truth About the Carbon Offset Industry