One of the problems is that there is no model. Approaches vary from one country to another. One of the objectives of the Copenhagen meeting was to develop a standardized model for measuring all reductions in greenhouse gas emissions. At another meeting, I saw that England and Sweden had systems for measuring reductions in greenhouse gas emissions. In any case, one size does not fit all countries, and that is one of the problems. The U.S. has its approach, and other countries have theirs.
On May 26th, 2009. See this statement in context.