Members of Congress hold diverse views about the value of international cooperation to address climate change. While some Members are convinced that human-induced climate change is a high priority risk that must be addressed through federal actions and international cooperation, others are not convinced of significant risk. Some are wary, as well, of international processes that could impose costs on the United States, undermine national sovereignty, or lead to trade advantages for other countries. The United States government has participated for more than two decades in various multilateral negotiations and actions aimed at addressing climate change. This report surveys the United Nations negotiations, from a primarily U.S. perspective. A table at the end of the report summarizes the chronology ( Table 1 ). Formal international negotiations were launched in December 1990 to address growing scientific and political concern about human-induced climate change. The negotiations on the 1992 United Nations Framework Convention on Climate Change (UNFCCC) marked the progress of decades of scientific research. Scientific conclusions—with uncertainties—have remained stable over two decades: greenhouse gas (GHG) emissions from human-related activities are very likely causing the major portion of climate change observed in recent decades. If changes continue, they could lead to adverse impacts on human societies and their environment, potentially including catastrophes. Predicting the timing, magnitude, and implications of change remains imprecise; many uncertainties may not be resolvable in a time frame consistent with making effective and efficient decisions to reduce the risks of climate change. The question of how to share any effort to address climate change has been a core challenge for international cooperation. Because emissions come from all countries, only concerted reductions by all major emitters can stabilize the rising GHG concentrations in the atmosphere. The United States historically has contributed the most—almost one-fifth of the rise of GHG concentrations since the Industrial Revolution. In 2007, however, China surpassed the United States as the leading emitter of GHG annually. In the future, the greatest growth in GHG emissions is expected from industrializing countries, such as China, India, and Brazil. These countries historically have contributed less, and still emit much less per person, than the United States and most other high-income countries. Arguably, the least developed and still industrializing nations have lower economic and governance capacities to address the problem. The size of effort and how to allocate it is a key element of negotiations. The primary issues for negotiation in 1990 remain the same today: when and by how much to reduce greenhouse gas emissions globally in order to achieve the UNFCCC's objective of avoiding " dangerous anthropogenic interference with the climate system "; how to share " common but differentiated responsibilities " among countries taking into account " historic contributions " and " respective capacities " of different people—in particular, the acceptable degree of participation of low-income countries; what mechanisms are best suited to assuring GHG reductions at the lowest cost, respecting national sovereignty and supporting " sustainable economic development " and " the eradication of poverty "; how cooperatively to understand the risks and facilitate adaptation to climate changes, especially by those people least able to cope on their own; and how to adapt international arrangements over time as science, social conditions, and capabilities evolve. At present, the United States is one of three of the 194 Parties to the UNFCCC that is not also Party also to the subsidiary Kyoto Protocol. (The other two are Canada and Andorra.) As a Party to the UNFCCC, the United States has general obligations to reduce its GHG emissions, report its emissions and be subject to international review, and assist lower-income countries, and other binding commitments. The industrialized Parties to the Kyoto Protocol ( Annex I Parties ), however, took on binding, quantitative commitments to reduce their GHG emissions to 5% below 1990 levels during 2008-2012 and agreed in 2012 to reduce these further during a second commitment period from 2013 to 2020. Most Parties have made voluntary pledges to GHG reduction targets or nationally appropriate mitigation actions under the 2009 Copenhagen Accord and the 2010 Cancun Agreements. Nonetheless, many non-Annex I Parties have opposed taking on legally binding commitments to abate GHG emissions. Many Annex I Parties have opposed taking on further legally binding commitments without participation by all Parties. The 2011 Durban Platform envisioned an end to two-track (developed versus developing) negotiations and provided a mandate to negotiate by 2015 a single outcome "with legal force" applicable to all Parties and that would take effect after 2020. How to pay for GHG reductions and adaptation measures is another key issue. The wealthiest Parties (including the United States) pledged "fast start" financing approaching $30 billion during 2010-2012, and a goal of mobilizing financing of $100 billion annually by 2020. Funding will come from public and private, bilateral and multilateral, and alternative sources. The most vulnerable developing countries had priority for the 2010-2012 funds. Reportedly, the fast-start financing goal was exceeded, but the pathway to meeting the 2020 pledge remains obscure. This report summarizes the process and principle issues and outcomes of the international climate change negotiations since 1990. Further, CRS has produced a series of reports on many aspects of the international climate change negotiations (and domestic issues) that can be accessed through the CRS website ( http://www.crs.gov/Pages/clis.aspx?cliid=2522 ) or by contacting CRS Inquiry at [phone number scrubbed]. This report summarizes the principal events and agreements, followed by a chronology at the end. The international negotiations launched in 1990 culminated in the 1992 adoption of the United Nations Framework Convention on Climate Change (UNFCCC) in Rio de Janeiro, Brazil. The U.S. Senate quickly gave its advice and consent, leading the United States to be the fourth nation to ratify the UNFCCC—the first among industrialized countries. As of November 1, 2013 195 governments were Parties to the UNFCCC. As a framework convention, this treaty provides the structure for collaboration and evolution of efforts over decades, as well as the first qualitative step in that collaboration. The UNFCCC does not, however, include measurable and enforceable objectives and commitments. The UNFCCC originally listed 35 of the most industrialized nations (including the United States) plus the European Economic Community (now the European Union, or EU) in Annex I. These Annex I Parties accepted specific commitments, particularly to take the lead in adopting national policies and undertaking measures with an aim to reduce human-related greenhouse gas (GHG) emissions to their 1990 levels by the year 2000. Annex I Parties also agreed to submit inventories of their emissions and sinks , and national communications of their UNFCCC-related policies and actions. The non-Annex I Parties were then low-income countries, though many are now middle- or high-income countries (e.g., Singapore). The UNFCCC also listed in Annex II the then-wealthiest Parties (including the United States), which committed to providing agreed new and additional financial resources to assist the developing country Parties to meet their obligations. By the time the treaty entered into force and the Conference of the Parties (COP) met for the first time in 1995, the Parties agreed that achieving the objective of the UNFCCC would require further, stronger, and binding GHG commitments. The 1995 Berlin Mandate for negotiations on a 1997 protocol deferred any new commitments for developing countries to later agreements. As a first enforceable step toward meeting the objective of the UNFCCC, the 1997 Kyoto Protocol promised to reduce the net GHG emissions of industrialized country Parties (Annex I Parties) to 5.2% below 1990 levels in the first commitment period of 2008 to 2012. It also pledged to assess the adequacy of these commitments early in the new century. The United States signed the Kyoto Protocol on November 12, 1998. In Congress, however, opposition was strong. In the "Byrd-Hagel" Resolution in July 1997, the Senate expressed its opposition (95-0 vote) to the terms of the Berlin Mandate, by stating that the U.S. should not sign any treaty that does not include specific, scheduled commitments of non-Annex I Parties in the same compliance period as Annex I Parties, or that might seriously harm the U.S. economy. The Kyoto Protocol (KP) was not submitted to the Senate for ratification by President Clinton, nor by his successor, President George W. Bush. Newly elected President Bush announced in 2001 that the United States would not become a Party because the Kyoto Protocol did not include GHG commitments by other large emitting non-Annex I countries and because of his conclusion that it would cause serious harm to the U.S. economy. As of November 1, 2012, 192 governments were Parties to the Kyoto Protocol. The United States and Andorra are the only Party to the UNFCCC never to join the Kyoto Protocol, while Canada withdrew from it in December 2012. Negotiations following the Kyoto Protocol particularly contested differentiation of commitments and assistance to developing countries, and slowed agreement on further steps under the UNFCCC. In 2007, Parties agreed to establish two tracks for negotiation of further commitments of Parties, one under the Kyoto Protocol and the other under the UNFCCC. The first track was a mandate among the Kyoto Protocol Parties (not including the United States) to pursue an amendment to the Protocol on further commitments of Annex I Parties for the period(s) beyond the year 2012. The first commitment period runs from 2008 through 2012. The second track was established in December 2007, when the Conference of the Parties (COP) to the UNFCCC agreed to a "Bali Action Plan" to negotiate new GHG mitigation targets for Annex I Parties, "nationally appropriate mitigation actions" for non-Annex I Parties, and other commitments for the post-2012 period.