UNFCCC stands for United Nations Framework Convention on Climate Change, which was adopted in 1992. The Convention has near universal membership (197 Parties) and is the parent treaty of the 2015 Paris Agreement and the 1997 Kyoto Protocol. The ultimate objective the UNFCC and its subsidiary treaties is to stabilize greenhouse gas concentrations in the atmosphere at a level that will prevent dangerous human interference with the climate system. Every year, the parties to the UNFCCC meet in what is known as the Conference of Parties (COP). The Paris Agreement was adopted in at COP 21. Greta Thunberg famously addressed the COP24 in 2018.
The UNFCCC eHandbook (link below) provides an overview of the UN climate change regime, including the UNFCCC, the Paris Agreement, and Kyoto Protocol. This handbook provides an excellent introduction and summary of the three major climate change treaties - the UNFCCC, Kyoto Protocol and Paris Agreement - as well as the negotiation process and issues covered by the UN climate change regime - mitigation, adaptation and support.
The Intergovernmental Panel on Climate Change (IPCC) is the United Nations body for assessing the science related to climate change. The IPCC was created in 1988 by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) to provide governments at all levels with scientific information that they can use to develop climate policies. IPCC reports are also a key input into international climate change negotiations.
The IPCC prepares comprehensive Assessment Reports which include contributions from each working group as well as a Synthesis Report integrating these contributions and any Special Reports prepared in that assessment cycle. The IPCC also prepares Special Reports focusing on specific issues and Methodology Reports that provide practical guidelines for the preparation of greenhouse gas inventories.
At the link below, you can find all three types of reports, as well as technical papers.
UN GA Resolutions are generally not binding, but may contribute to the development of customary international law. See Markus Benzing, International Organizations or Institutions, Secondary Law, Max Planck Encyclopedias of International Law, last updated Mar. 2007; Secretariat's legal opinion of 9 May 1986, on "Questions relating to the voting procedure and decision-making process of the General Assembly—General rule applicable to the calculation of the majority required for the adoption of resolutions and decisions by the General Assembly—Exceptions to the rule—Effect of absence or non-participation on the binding force of resolutions and decisions", published in the UN Juridical Yearbook, 1986, p. 274
Protection of Global Climate for Present and Future Generations of Mankind (these are just a few of the resolutions passed by the UNGA on climate change. To find additional resolutions, refer to the UN Digital Library searches below)
UN Digital Library Search:
Subject Heading Search: Climate Change Filtered to UN GA and Resolutions and Decisions
Search the Digital Library for decisions and resolutions by UN Bodies regarding climate.
The International Law Commission, which is charged with the "codification" of international law is working on several topics related to climate change including:
Protection of the Atmosphere
Sea Level Rise and International Law
In addition, its draft articles and reports on several topics such as the identification of customary law, prevention of transboundary harm from hazardous activities and state responsibility are relevant in interpreting state liabilities, duties, and obligations under international law with regard to climate change.
The Oxford Handbook of International Climate Change Law by 
Climate Change, Cattle, and the International Legal Order
The Environmental Rule of Law for Oceans: Designing Legal Solutions by 
Law, Climate Emergency and the Australian Megafires by 
Legal Issues on Climate Change and International Trade Law by 
Negotiating the Paris Agreement: The Insider Stories by 
Non-governmental Actors in International Climate Change Law: The Case of Arctic Indigenous Peoples by 
