The attempt to develop international cap and trade markets for anthropogenic greenhouse gas emissions, ultimately aiming to determine a global price for carbon, is the most extensive attempt ever made to use market-mimicking mechanisms to deal with an environmental externality. Addressed to the problem of climate change, it is an exercise in the adjustment of the social welfare function on a global scale, and it envisages expenditures which will run into trillions of dollars. Focusing on the operation of the Clean Development Mechanism, the most important of the three flexible mechanisms for carbon trade established under the Kyoto Protocol, it will be argued that carbon trading which will reduce emissions in line with any of the targets se...