The Kyoto Protocol aims to reduce greenhouse gas emissions by letting countries trade emission credits. A study using a global model looked at how three trading scenarios could help countries meet their emissions targets. The research found that the more freedom countries have to use trading mechanisms, the more they benefit. However, the benefits are not spread evenly, with countries having high emission reduction costs benefiting most. Limiting trading options not only reduces efficiency gains for some countries but also hampers financial support for developing countries through the clean development mechanism.