Recognizing that climate change of the Earth had been adversely affected by the increase of greenhouse gas generated from human activities, the United Nations, for the purpose of reducing and controlling the emission of anthropogenic greenhouse gas, passed the United Nations Framework Convention on Climate Change (UNFCCC) in its New York headquarter in May 1992. The UNFCCC was later submitted to the United Nations Conference on Environment and Development held in Rio, Brazil in June of the same year and opened for signing. One hundred and fifty-five countries participating in the conference signed the UNFCCC.  The convention officially entered into force in 1994 after it had been ratified by fifty signature parties in December 1993. 

    Since 1994, The Conference of Parties (COP) has been convened annually to deliberate the future development of the convention. According to the UNFCCC, signature country parties shall exchange information regarding emission of greenhouse gas, cooperate to develop strategies effectively reducing emission of greenhouse gas and assist developing countries decrease emission of greenhouse gas by funding or techniques. Moreover, each party country shall make preparations for climate changes caused by greenhouse gas. Five principles are explicitly stated in the UNFCCC: (1) common but differentiated responsibilities for country parties; (2) full consideration of the specific needs and special circumstances of developing country parties; (3) precautionary principle; (4) sustainable development: (5) an open international economic system.    

    Although UNFCCC, a framework convention, provides for the principles regulating emission of greenhouse gas, it does not stipulate the strategies specifically. Therefore, the Kyoto Protocol adopted in the COP3 held in 1993 in Kyoto, Japan, was a supplement to the UNFCCC. The Kyoto Protocol sets clearly the agenda for carbon dioxide emission reduction of industrialized party countries by the year 2012. 

    Owing to that the Kyoto Protocol only sets the carbon dioxide emission reduction agenda to 2012, the COP13 in 2007 has achieved the decision that a new stipulation concerning carbon dioxide reduction shall be discussed in COP15 held in 2009. Other main topics will also be discussed in the conference this year, including the source and use of the fund for global climate change, how to balance greenhouse gas emission reduction and economic development of developing countries as well as how developed countries support and assist developing countries.