The United Nations Framework Convention on Climate Change (UNFCCC)
The impetus that initiated the efforts to address and regulate climate change was largely the 1987 discovery of the stratospheric Antarctic ozone hole and the potential threat that might pose the international community. Indeed, the consequence that environmental degradation would have on human development it was the matter of discussion in the Brundland report of the World Commission on Environment and Development: “Our Common Future" at the same year.  However, the regulatory efforts were substantially pinnacled at the 1992 United Nations Conference on Environment and Development (UNCED) in Rio de Janeiro with the adoption of the United Nation Convention on Climate Change (UNFCCC).  An earlier wave of international environmental activity, culminated in the 1972 Stockholm Conference and the establishment several years later of the United Nations Environment Programme (UNEP), had tended to focus on local, acute, and relatively reversible forms of pollution, for example, oil spills and dumping of hazardous wastes at sea, by regulating particular pollutants.  However, the adoption of the UNFCCC the cycle of climate activity including Kyoto Protocol, rode a wave of global environmental activity, which has focused not merely on environmental protection per se, but on the more general economic and social policies needed to achieve sustainable development. 
Since the international climate change negotiations have commenced the climate change regime has largely developed in four phases. This chapter it is organized chronologically in the basic phases which follow the main negotiation stages that the climate regime has experienced. The first phase covers the foundational period from 1970 until 1990, during which scientific concern about global warming developed and transformed into a policy issue. The second phase covers the period leading up to the adoption of the Climate Change Convention in March 1994, when the institutionalization of the climate regime became definitive. The third phase, running from 1995 to 2005, involved the negotiation and elaboration of the Kyoto Protocol, which sets out quantitative emission reduction targets for developed countries through 2012, and establishes market-based mechanisms for achieving those targets. The last phase which the Copenhagen Conference had been intended to conclude addresses the post-2012 period, after the Kyoto Protocol’s first commitment period ends. 
2.1 The Pre-1990 Phase: Framing the Problem
The development of the climate change issue was primarily raised in the scientific field in the effort to understand and evaluate the consequences of the greenhouse problem. However, the challenge of climate change and its implications for society began to get sporadic attention outside of the scientific arena in the 1970s and enhanced significantly in the late 1980s. At that period the interconnection of environment and development had become progressively more popular after a series of meetings and reports. First, the 1971 Founex Report on Development and Environment  accentuate the necessity to consider environmental concerns under the light of development and second the 1972 UN Stockholm Conference on the Human Environment which marked the beginning of modern international environmental law, which is characterized by the transformation in the interests of states from trans-boundary environmental matters to global environmental concerns. 
2.1.1 Climate Change in the Scientific Arena
The First World Climate Conference in February 1979 in Geneva organized by the World Meteorogical Organization was one of the foremost international scientific fora on climate change and it was joined by scientists from a broad range of disciplines. The Conference led to the establishment of the World Climate Programme and the World Climate Research Programme.  By the mid-1980s, scientists concluded that global warming beyond natural variability was occurring and that this was in large part due to human activity and the increase of anthropogenic emissions of greenhouse gases (GHGs). Hence, in the 1985 International Conference on Assessment of the Role of Carbon Dioxide and of Other Greenhouse Gases in Climate Variations and Associated Impacts, held in Villach, Austria, scientists called on politicians to collaborate in the exploration of policies to mitigate human-induced climate change. By the late 1980s, after a series of incidents and discoveries, including the leak of poisonous gas from a chemical plant at Bhopal, India, the explosion and radioactive release from Chernobyl, Ukraine and the discovery of the ozone hole in the Antarctic ozone enhanced the already existing urgency for global action. Indeed, the World Commission on Environment and Development (WCED) which was appointed by the UN in 1983 to “improve well-being in the short-term without threatening the local and global environment in the long term" in its 1987 Brundtland Report defined the first major international conceptual recognition of Sustainable Development as “the development which meets the needs of the present without compromising the ability of future generations to meet their own needs"  and contains two key concepts:
the concept of 'needs', in particular the essential needs of the world's poor, to which overriding priority should be given; and
the idea of limitations imposed by the state of technology and social organization on the environment's ability to meet present and future needs.
In the 1988 ‘Toronto Conference on the Changing Atmosphere’ governments and scientists together discussed actions to combat climate change. At this conference, industrialized countries governments agreed to voluntarily cut CO2 emissions by 20% by the year 2005, the so-called "Toronto target". This meeting was also critical in the establishment of the Intergovernmental Panel on Climate Change (IPCC) under the auspices of the United Nations Environment Programme and the World Meteorological Organization. An international grouping of over 300 climate scientists charged with reviewing and reporting on the latest international science, impacts and responses to climate change for the purpose of assessing information relevant for the understanding of the risk of human-induced climate change. 
2.1.2 Climate Change in the Political Arena
In the light of these developments, finally the climate issue was raised and discussed in the UN General Assembly which included the item “Protection of global climate for present and future generations of mankind" in the agenda of its forty-third session. By resolution 43/53 on 6 December 1988, adopted under that item, it recognized inter alia that “climate change is a common concern of mankind" and determined that “necessary and timely action should be taken to deal with climate change within a global legal framework". 
After several high levels international meetings such the 1989 Hague and Noordwijk Conferences, and the 1990 Second World Climate Conference where many industrialized countries agreed to starts efforts to stabilize their greenhouse gas emissions, on 21 December 1990, recalling the latter resolution, as well as resolution 44/207 of 22 December 1989 under the same item, the General Assembly adopted resolution 45/212.  This resolution introduced a single intergovernmental negotiating procedure under the auspices of the General Assembly, supported by the United Nations Environment Programme and the World Meteorological Organization, for the preparation by an Intergovernmental Negotiating Committee of an effective framework convention on climate change taking into consideration proposals submitted by States participating in the negotiating process, the work of the Intergovernmental Panel on Climate Change and the results achieved at international meetings on the subject. In the same resolution, the General Assembly considered that these negotiations should be completed prior to the United Nations Conference on Environment and Development and that a framework convention be opened for signature during the conference. 
However, even from the 1990 Second World Climate Conference in Geneva, it became obvious that there was a “North-South" divide on how developed and developing countries viewed climate change. While for developed countries, at that time, it was mainly a scientific and environmental issue, the developing countries emphasized on the implications for poverty and development of any future regime. These misleading joint positions of the North and South were grounded on diverse and often different underlying interests with respect to obligations. In the first group, the majority of Organisation for Economic Cooperation and Development countries favored the adoption of an agreement that would reduce global GHG emissions, though there was no agreement by how much these should be reduced. In contrast, the United States, agreeing in principle to the need for an environmental agreement, did not want to be subject to any obligation to reduce emissions. The second group was united in the argument that the new legal instrument must not obstruct their economic development. Apart from this position, interests were divided: while the oil exporting countries feared for their revenue streams under a new instrument that might restrict the use of fossil fuels, and charcoal consuming countries were concerned about the future use of their primary source of energy, the Small Island States and States with low-lying coastal areas created an alliance to protect themselves from the threat of rising oceans.
However, developing countries felt that their concerns were not properly addressed by the scientifically focused IPCC process and rejected the proposal of a negotiating committee that would work under the auspices of WMO and UNEP. Thus, an International Negotiating Committee for a Framework Convention on Climate Change (INC) was established under the auspices of the United Nations General Assembly (resolution 45/212 of 21 December 1990). The INC was open to all Member States of the United Nations and its specialized agencies. Its mandate was “to negotiate a framework convention, containing appropriate commitments, and any related legal instruments as might be agreed upon" in time to be opened for signature at the 1992 United Nations Conference on Environment and Development (UNCED) in Rio de Janeiro.
2.2 Second Phase: The Adoption of the UNFCCC
The necessity for an effective climate regulation soon developed to an international consensus that States should also consider the elaboration of a universal legally-binding convention on climate change, which would address emissions of greenhouse gases not covered under the Ozone Layer protection regime, i.e., the 1985 Vienna Convention for the Protection of the Ozone Layer and the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer.
The Earth Summit in Rio, as it was called, marked the first international attempt to outline action plans and strategies for moving towards a more sustainable project of development. The outcome of this effort was the Rio Declaration on Environment and Development, the Statement of principles for the Sustainable Management of Forests, the Convention on Climate Change and the Convention on Biological Diversity, and a promising action agenda on worldwide sustainable development (Agenda 21). At the end of the meeting it was agreed that a five year review of Earth Summit progress would be made in 1997 by the United Nations General Assembly meeting in special session. The United Nations Framework Convention on Climate Change was open for signature at UNCED from 4 to 14 June 1992, and thereafter at United Nations Headquarters in New York until 19 June 1993. By that date, the Convention had 165 signatories. It entered into force on 21 March 1994 and it has near universal membership.
Climate change is defined by the Convention as “change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods" (article 1 (2)). The long-term objective of the Convention and its related legal instruments is “to achieve […] the stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system" (article 2). 
The challenges posed by climate change have given rise to the issue of how to distribute the burden of reducing greenhouse gas (GHG) emissions among countries with varying development contexts and capabilities. The Convention addresses these concerns by laying down principles agreed upon by the Parties, which are to be used by Parties in guiding their efforts to achieve the object and purpose of the Convention. This has also been accompanied by the creation and placement of countries into three categories. Annex I includes the industrialized countries that were members of the OECD (Organization for Economic Co-operation and Development) in 1992, plus countries with economies in transition (EIT) including the Russian Federation, the Baltic States, and several central and eastern European states. Annex II takes in OECD members of Annex I, but not the EIT Parties and non-Annex I countries are mostly developing countries.
The UNFCCC, which provide the foundation of a new international climate change régime, specify several “principles" in its Article 3. As the definition of “principles" is not provided for in the UNFCCC, the chapeau of Article 3 of the UNFCCC states that “in their actions to achieve the objective of the Convention and to implement its provisions, the Parties shall be guided, inter alia", by those principles.
2.2.2 Normative Framework of the UNFCCC
Article 3 of the UNFCCC establishes principles to guide the Parties in achieving the objective of the Convention and in implementing their commitments. By setting up the legal institutional framework for implementation and future action,  the principles are the boundaries by which to shape the next developments. In this way they have a broader a role in also advancing and forming international law.  These principles are important interpretative tools for the primary provisions contained in both the Convention and the Kyoto Protocol. The principles laying in Article 3 together inter alia with those mentioned in the Preamble inform the legal obligations of the Parties Because of the almost universal membership to the Convention it has been argued that they could also provide legal reasoning for primary duties to prevent dangerous climate change outside the framework of the climate regime.  . However, although the legal nature of the Principles has been a subject of controversy the negotiation history gives some evidence of the intention of the Parties to avoid giving legally binding effect to those principles while Article 3 explicitly provides that parties “shall" apply the UNFCCC Principles.
A. Common but Differentiated Responsibilities
Practices of facing States in a certain category differently from others are not necessarily new to the climate change regime. Even in the WTO law, the principle of the Most Favorite Nation (MFN) which is the foundation of the organization and request the same treatment for all participating members accept several exceptions for environmental purposes and for developing countries (Special and Differential Treatment (SDT)). In recent interpretation of WTO law, there is movement towards an obligation to consider the particular economic, social and environmental situation of developing countries when adopting environmental measures. The WTO dispute settlement panel in the Shrimp case expressly mentioned the principle of ´common but differentiated responsibilities in its conclusions.
In the context of environmental protection, this differential treatment is conceptualized as common but differentiated responsibilities and it can be found in many environmental regimes such as Montreal Protocol, Article 5, the UN Convention on Biological Diversity, Article 20(1), the UN Convention to Combat Desertification, Articles 5, 6(b), and 20 etc. The concept of common and differential responsibilities in the climate regime it can be found in both, in the Principle 7 of the Rio Declaration on Environment and Development and in Article 3 (1) of the UNFCCC. The Rio Declaration states: “In view of the different contributions to global environmental degradation, States have common but differentiated responsibilities. The developed countries acknowledge the responsibility that they bear in the international pursuit of sustainable development in view of the pressures their societies place on the global environment and of the technologies and financial resources they command." Similar language exists in the Framework Convention on Climate Change; parties should act to protect the climate system “on the basis of equality and in accordance with their common but differentiated responsibilities and respective capabilities." However, there are divergent views on the grounds for differentiation applicable to the concept of CBDR. From the stipulations in the Rio Declaration and the UNFCCC mentioned above and the exchange of views among States concerning them, several premises for differentiation in the context of global environmental protection could be identified. For example developing countries argue that historically industrialized countries generating the largest share of global emissions of greenhouse gases and they should bear the cost. On the other hand many powerful developing countries suggest that developing countries are entitled to fewer and less stringent commitments and financial/technical assistances, in the light of their necessity for development. On the other hand Developed countries argue that having resources and capabilities to take responsive measures should lead the environmental protection and with some major developing countries they should undertake commitments to reduce their emissions and to promote a large participation in international environmental treaties.
The principle of common but differentiated responsibility includes two fundamental elements. The first concerns the common responsibility of States for the protection of the environment, or parts of it, at the national, regional and global levels. The second concerns the need to take into account the different circumstances, particularly each State’s contribution to the evolution of a particular problem and its ability to prevent, reduce and control the threat.
Common responsibility describes the shared obligations of two or more States towards the protection of a particular environmental resource. Common responsibility is likely to apply where the resource is shared, under the control of no state, or under the sovereign control of a state, but subject to a common legal interest (such as biodiversity – termed a common concern of humankind). The concept of common responsibility evolved from an extensive series of international laws (see section III below) governing resources labelled as ‘common heritage of mankind’ or of ‘common concern.’
Differentiated responsibility of States for the protection of the environment is widely accepted in treaty and other State practices. It translates into differentiated environmental standards set on the basis of a range of factors, including special needs and circumstances, future economic development of countries, and historic contributions to the creation of an environmental problem. The Stockholm Declaration emphasized the need to consider “the applicability of standards which are valid for the most advanced countries but which may be inappropriate and of unwarranted social cost for the developing countries."
In summary, States have common responsibilities to protect the environment and promote sustainable development, but due to different social, economic, and ecological situations, countries must shoulder different responsibilities. The principle therefore provides for asymmetrical rights and obligations regarding environmental standards, and aims to induce broad State acceptance of treaty obligations, while avoiding the type of problems typically associated with a lowest common denominator approach. The principle also reflects the core elements of equity, placing more responsibility on wealthier countries and those more responsible for causing specific global problems. Perhaps more importantly, the principle also presents a conceptual framework for compromise and co-operation in effectively meeting environmental challenges.
At any case, from a legal point of view, it is necessary to explore the adequate basis of responsibility introduced in the climate change régime. It can be argued that the concept of responsibility in the above provisions should be understood to signify that something is imposed upon States. Therefore, in this context, the nature of this imposition should be clarified further. Some advocate that “responsibility" used in the documents above simply signifies duty to be fulfilled by States concerned. They imply that “duty" is not a legal obligation in the strict sense but is merely a moral requirement, while the concept of “obligation" usually signifies a legally binding imposition. Others, not showing such a clear line of distinction, stress that the concept of “responsibility" in the above provisions does not in itself generate concrete obligations for States but serves as a guiding principle for articulating specific rules in a given régime.
However, although the Framework Convention on Climate Change embraces several important legal concepts the treaty itself sets no mandatory limits on greenhouse gas emissions for individual countries and contains no enforcement mechanisms.  In that sense, the treaty is considered legally non-binding. Therefore, the concept cannot be regarded as a specific international rule by which States are obligated to act, or refrain from acting in a specific way so the concept does not in itself oblige States to conduct themselves in a concrete manner. Therefore, the concept of CBDR can serve just as a guiding principle in negotiation for articulating new normative documents to tackle the climate change threat.
B. The Precautionary Principle
The precautionary principle has been commonly used in international environmental law and has been applied to areas such as climate change, hazardous waste and ozone layer depletion and biodiversity. 
The principle adopted in the existing climate efforts to address climate change despite many doubts at that time about the science and impacts of the global warming phenomenon on global community.  As the negotiation process towards the UNFCCC show participating members agreed that if there is a possibility of a prospective damage, they should not wait until the risk can be scientifically confirmed before taking action to avoid it and apply the precautionary principle, instead of the traditional reactive wait-and-see approach.  Based on this rationale, the UNFCCC specify this concept in Article 3 (3) as one of the ‘principles’ by which the Parties shall be guided in their actions:
The Parties should take precautionary measures to anticipate, prevent or minimise the causes of climate change and mitigate its adverse effects. Where there are threats of serious or irreversible damage, lack of full scientific certainty should not be used as a reason for postponing such measures, taking into account that policies and measures to deal with climate change should be cost effective so as to ensure global benefits at the lowest possible cost. […]
However, Article 3.3 does not make cost effectiveness selective criterion for the kind of environmental measures to be implemented. It only requires consideration of cost effectiveness be taken in account. The phrase ‘taking into account that policies and measures to deal with climate change should be cost effective so as to ensure global benefits at the lowest possible cost’ refers to adaptation and mitigation without at any case deciding whether mitigation or adaptation should be chosen as a preferred measure. 
It is also a fundamental component of the concept of ecologically sustainable development (ESD) and has been defined in Principle 15 of the Rio Declaration (1992)  :
Where there are threats of serious or irreversible environmental damage, lack of full scientific certainty should not be used as a reason for postponing measures to prevent environmental degradation.