The Conference of the Parties is the "supreme body" of the Climate Change Convention. The vast majority of the world’s states are members – 185 as of July 2002. The Convention enters into force for a state 90 days after that state ratifies it. The COP held its first session in 1995 and will continue to meet annually unless decided otherwise. (The various subsidiary bodies that advise and support the COP meet more frequently.)

The COP must promote and review the Convention’s implementation. The Convention states that the COP must periodically examine the obligations of the Parties and the institutional arrangements under the Convention. It should do this in light of the Convention's objective, the experience gained in its implementation, and the current state of scientific knowledge.

Progress is reviewed largely through the exchange of information. The COP assesses information about policies and emissions that the Parties share with each other through their "national communications." It also promotes and guides the development and periodic refinement of comparable methodologies, which are needed for quantifying net greenhouse gas emissions and evaluating the effectiveness of measures to limit them. Based on the information available, the COP assesses the Parties’ efforts to meet their treaty commitments and adopts and publishes regular reports on the Convention's implementation.

Mobilizing financial resources is vital for helping developing countries carry out their obligations. They need support so that they can submit their national communications, adapt to the adverse effects of climate change, and obtain environmentally sound technologies. The COP therefore oversees the provision of new and additional resources by developed countries.

The COP is also responsible for keeping the entire process on track. In addition to the two subsidiary bodies established under the Convention – the Subsidiary Body for Implementation (SBI) and the Subsidiary Body for Scientific and Technological Advice (SBSTA) – the COP can establish new ones to help it with its work, as it did at its first session (see below). The COP reviews reports from these bodies and guides them. It must also agree and adopt, by consensus, rules of procedure and financial rules for itself and the subsidiary bodies (as of mid-2002 the rules of procedures had not been adopted and, with the exception of the rule on voting, are being "applied").

The Conference of the Parties held its first session (known as COP-1) in Berlin. From 28 March - 7 April 1995, Berlin was the site of the first global climate change meeting attended by ministers since the 1992 Rio "Earth Summit". The Convention required COP-1 to review whether the commitment by developed countries to take measures aimed at returning their emissions to 1990 levels by the year 2000 was adequate for meeting the Convention’s objective. The Parties agreed that new commitments were indeed needed for the post-2000 period. They adopted the "Berlin Mandate" and established a new subsidiary body, the Ad hoc Group on the Berlin Mandate (AGBM), to draft "a protocol or another legal instrument" for adoption at COP-3 in 1997. The Berlin meeting also started the review process to consider the implementation of the Convention by discussing a compilation and synthesis of the first 15 national communications submitted by developed countries.

The second session of the COP took stock of progress on the Berlin Mandate. Ministers stressed the need to accelerate talks on how to strengthen the Climate Change Convention. Their Geneva Declaration endorsed the 1995 Second Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) "as currently the most comprehensive and authoritative assessment of the science of climate change, its impacts and response options now available." Held at the Palais des Nations in Geneva from 8-19 July 1996, COP-2 also considered the review process for national communications and decided on the contents of the first national communications that developing countries were to start submitting in April 1997.

The third session of the Conference of the Parties adopted the Kyoto Protocol. The Parties met in Kyoto, Japan from 1-11 December 1997 to conclude the Berlin Mandate process. The Protocol they crafted is a legally binding agreement under which industrialized countries are to reduce their collective emissions of six greenhouse gases by 5.2% by 2008-12, calculated as an average over these five years. To help Parties reduce emissions cost-effectively while promoting sustainable development, the Protocol includes three "mechanisms": the clean development mechanism, an emissions trading regime, and joint implementation. COP-3 also considered funding, technology transfer, and the review of information under the Convention.

COP-4 adopted a two-year Plan of Action to finalize the Protocol's outstanding details. To ensure that the agreement would be fully operational when it entered into force, governments agreed to a COP-6 deadline for deciding just how its "mechanisms" will function. The Plan also addressed compliance issues, policies and measures, and Convention-related issues such as the transfer of climate-friendly technologies to developing countries. COP-4 was held in Buenos Aires from 2 - 13 November 1998.

COP-5 set an aggressive timetable for completing work on the Protocol. This included establishing the process that negotiators would follow over the next 12 critical months. Other decisions settled important substantive issues. For example, agreement was reached on how to improve the rigor of national reports from industrialized countries and how to strengthen the guidelines for measuring their greenhouse gas emissions. Action was also taken to address bottlenecks in the delivery and consideration of national communications by developing countries.

COP-6 adopted a broad political agreement on the Protocol’s operational rulebook. Meeting from 6 – 25 November, COP-6 made progress in outlining a package of financial support and technology transfer to assist developing countries in contributing to global action on climate change. But key political issues – including an international emissions trading system, a "clean development mechanism", the rules for counting emissions reductions from carbon sinks, and a compliance regime – could not be resolved in the time available. The session was therefore suspended and resumed some months later in Bonn, from 16 – 27 July. This time the Parties were able to reach agreement on the broad political principles underlying the rulebook.

COP-7 finalized the Protocol’s institutions and detailed procedures. The finalized Kyoto rulebook specifies how to measure emissions and reductions, the extent to which carbon dioxide absorbed by carbon sinks can be counted towards the Kyoto targets, how the joint implementation and emissions trading systems will work, and how to ensure compliance with the commitments.