"Delegations of 195 nations adopted, on December 12, 2015, a Paris Agreement that creates a structure for nations to pledge to abate their greenhouse gas (GHG) emissions, to adapt to climate change, and to cooperate to these ends, including financial and other support. A single framework to promote transparency and track progress of Parties' efforts applies, for the first time, to all Parties. The Parties also adopted a decision to give effect to the Paris Agreement. Both the Decision and the Agreement (hereinafter capitalized) are intended to be legally binding on Parties to the United Nations Framework Convention on Climate (UNFCCC) and the new Agreement, respectively, though not all provisions within them are mandatory. Both are subsidiary to the UNFCCC, which the United States ratified with the advice and consent of the Senate (Treaty Document 102-38, October 7, 1992) and entered into force in 1994. Whether the new Paris Agreement or Decision would require Senate advice and consent depends on the content of the agreements. In particular, if either were to contain new legal obligations on the United States, it would favor requiring Senate consent to ratification. However, the United States and other Parties to the UNFCCC accepted many legally binding obligations when they ratified the Convention, including control of greenhouse gas (GHG) emissions, preparation to adapt to climate change, international cooperation and support, and regular reporting of emissions and actions with international review. Some have argued that the Paris Agreement does not require more of the United States than it is already obligated to do under the UNFCCC, while others have argued that it does."
CRS Insight, IN10413
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html