The Convention was complemented by the 1997 to assess progress in dealing with climate change, and beginning in the mid-1990s. The Kyoto Protocol was establishing legally binding obligations for developed countries to reduce their greenhouse gas emissions. Countries that ratify the Kyoto Protocol are assigned maximum carbon emission levels and can participate in carbon credit trading. Emitting more than the assigned limit will result in a penalty for the violating country in the form of a lower emission limit in the following period. The total amount of greenhouse gases produced to directly and indirectly support human activities, usually expressed in equivalent tons of carbon dioxide (CO2).