the primary cause of global warming is carbon dioxide, which enters the atmosphere in various amounts from different countries but is distributed equally around the globe within a year. in order o solve this problem, some economist have argued that carbon dioxide emissions should be reduced in countries where the costs are least, with the countries that bear the burden being compensated by the res of the world. Could a global system of emission permits similar to the European trading scheme achieve this? where does efficiency of the permit system come from? why is international cooperation necessary to reach an efficient outcome