Many governments hold that environmental degradation and climate change pose international and trans-boundary risks to human populations, economies, and ecosystems, as well as potential risks to national security. To confront these challenges, governments have negotiated various international agreements to protect the environment, reduce pollution, conserve natural resources, and promote sustainable growth. While some agreements call upon industrialized countries to take the lead in addressing these issues, many recognize that efforts by wealthier countries alone are unlikely to be sufficient without similar measures being taken in lower-income countries. However, lower-income countries, which tend to prioritize poverty reduction and economic growth, may not have the financial resources, technological expertise, or institutional capacity to deploy environmentally protective measures on their own. Therefore, international financial assistance has been a principal method for governments to support actions on global environmental problems in lower-income countries. The United Nations Framework Convention on Climate Change (UNFCCC, 1992) was the first international treaty to acknowledge and address human-driven climate change. The United States ratified the treaty in 1992 (U.S. Treaty Number: 102-38). Among the obligations outlined in Article 4, higher-income Parties (i.e., those listed in Annex II of the Convention, which were members of the Organization for Economic Cooperation and Development in 1992) committed themselves to seek to provide unspecified amounts of "new and additional financial resources to meet the agreed full costs incurred by developing country Parties in complying with their obligations" under the Convention. Further, "the implementation of these commitments shall take into account the need for adequacy and predictability in the flow of funds and the importance of appropriate burden sharing among the developed country Parties." Over the past several decades, the United States has delivered financial and technical assistance for climate change activities in the developing world through a variety of bilateral and multilateral programs. U.S.-sponsored bilateral assistance has come through programs at the U.S. Agency for International Development, the U.S. Department of State, the Millennium Challenge Corporation, the Export-Import Bank, and the Overseas Private Investment Corporation, among others. U.S.-sponsored multilateral assistance has come through contributions by the U.S. Departments of State and the Treasury to environmental funds at various international financial institutions and organizations such as the Global Environment Facility (GEF), the Green Climate Fund (GCF), the U.N. Development Program, the U.N. Environment Program, the UNFCCC's Special Climate Change Fund and Least Developed Country Fund, the World Bank's Climate Investment Funds (including the Clean Technology Fund and the Strategic Climate Fund), and the Forest Carbon Partnership Facility, among others. To facilitate the provision of climate finance under the UNFCCC, the Convention establishes a financial mechanism to provide funds to developing country Parties. Article 11 of the Convention states that the operation of the financial mechanism can be entrusted to one or more existing international entities. The GEF was established in 1991 and subsequently became an official operating entity of the financial mechanism of several international environmental agreements , including the UNFCCC. The relationship between the UNFCCC and the GEF is outlined in a memorandum of understanding contained in UNFCCC decisions 12/CP.2 and 12/CP.3. The George H. W. Bush Administration supported the establishment of the GEF in 1991. The United States has made commitments to all six GEF resource replenishments, including $430 million in 1994, $430 million in 1998, $430 million in 2002, $320 million in 2006, $575 million in 2010, and $546 million in 2014, for a total of $2.732 billion. U.S. commitments correspond to about 13% of GEF's total during the history of the institution. U.S. disbursements to the GEF since 1994 have totaled approximately $2.2 billion. In 2009, the Conference of Parties (COP) to the UNFCCC in Copenhagen, Denmark, took note of a non-legal political document called the Copenhagen Accord. The following year, in Cancun, Mexico, the COP officially adopted many of the accord's elements in the Cancun Agreements, including several quantified financial arrangements: Fast start financing . The agreement puts forth a collective commitment by developed country Parties (not specified in the text) to seek to provide new and additional resources approaching $30 billion for the period 2010-2012 to address the climate finance needs of developing countries (1/CP.16§95). 2020 pledge . The agreement takes note of the pledge by developed country Parties (not specified in the text) to achieve a goal of mobilizing jointly $100 billion per year by 2020 to address the climate finance needs of developing countries (1/CP.16§98). Sources. The agreement states that "funds provided to developing country Parties may come from a wide variety of sources, public and private, bilateral and multilateral, including alternative sources" (1/CP.16§99). In 2015, the COP to the UNFCCC in Paris, France, adopted the Paris Agreement (PA). The PA builds upon the Convention and—for the first time—brings all nations into a common framework to undertake efforts to combat climate change, adapt to its effects, and support developing countries in their efforts. Article 9 of the PA reiterates the obligation in the Convention for developed country Parties, including the United States, to seek to mobilize financial support to assist developing country Parties with climate change mitigation and adaptation efforts (Article 9.1). Also, for the first time under the UNFCCC, the PA encourages all Parties to provide financial support voluntarily, regardless of their economic standing (Article 9.2). The agreement states that developed country Parties should take the lead in mobilizing climate finance and that the mobilized resources may come from a wide variety of sources. It adds that the mobilization of climate finance "should represent a progression beyond previous efforts" (Article 9.3). The COP Decision to carry out the PA (1/CP.21) uses exhortatory language to restate the collective pledge by developed countries of $100 billion annually by 2020 and calls for continuing this collective mobilization through 2025. In addition, the Parties agree to set, prior to their 2025 meeting, a new collective quantified goal for mobilizing financial resources of not less than $100 billion annually to assist developing country Parties. On June 1, 2017, President Donald Trump announced his intention to withdraw from the PA. Under the provisions of the PA, this could not be completed before November 4, 2020. Other CRS products examine the legal and policy implications of this announcement. The 2009 Copenhagen Accord opened the way for the GCF to be designated as an operating entity of the financial mechanism of the UNFCCC (similar to the GEF). Parties agreed to the design of the GCF during the 2011 COP in Durban, South Africa. The GCF is intended to operate at arm's length from the UNFCCC, with an independent board, trustee, and secretariat. The GCF is to be "accountable to and function under the guidance of the Conference of Parties" (i.e., similar in legal structure to the GEF), as opposed to "accountable to and function under the guidance and authority of the Conference of Parties" (i.e., similar in legal structure to the Adaptation Fund). The purpose of the fund is to assist developing countries in their efforts to combat climate change through the provision of grants and other concessional financing. The GCF is capitalized by "financial inputs from developed country Parties to the Convention" and "may also receive financial inputs from a variety of other sources, public and private, including alternative sources." The GCF became operational in the summer of 2014. Parties have pledged approximately $10.3 billion for the initial capitalization of the fund. The Barack Obama Administration pledged $3 billion over four years in November 2014. The U.S. Department of State made two contributions of $500 million to the GCF on March 8, 2016, and on January 17, 2017. The funds were obligated with FY2016 budget authority from the agency's Economic Support Fund—an account under the function 150 and Other International Programs budget. The Foreign Assistance Act of 1961, as amended (P.L. 87-195; part II, Chapter 4), provides the President authority to use the Economic Support Fund "to furnish assistance to countries and organizations, on such terms and conditions as he may determine, in order to promote economic or political stability." No contribution has been made to the GCF with FY2017 budget authority. The Trump Administration's FY2018 budget request, released on May 23, 2017, proposes to "eliminate U.S. funding for the Green Climate Fund (GCF) in FY2018, in alignment with President Trump's promise to cease payments to the United Nations' climate change programs." President Trump has denounced the GCF, stating that the fund would "redistribute wealth out of the United States" and that "billions of dollars that ought to be invested right here in America will be sent to the very countries that have taken our factories and our jobs away from us." Nevertheless, the U.S. disbursement of $1 billion to the GCF under the Obama Administration ensures that the United States remains a member of the GCF board through the initial phase of capitalization. The Trump Administration has not stated whether it will retain its board membership. A State Department official reportedly said that "future U.S. engagement with the GCF will be decided as part of the wider internal process to further develop our policy on climate change." The relationship of the GCF to the United States' other climate finance commitments can be outlined as follows: UNFCCC 2020 pledges . The collective pledge by developed country Parties to the goal of mobilizing jointly $100 billion per year by 2020 is not tied directly to the GCF, nor is it tied directly to public funding.