Short answers, pulled from the story.
The UNFCCC was opened for signature on the 4th of June 1992 at the Earth Summit in Rio de Janeiro. By the 12th of June 1992, 154 nations had signed. The treaty entered into force on the 21st of March 1994.
The UNFCCC's main objective, set out in Article 2, is the stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous human-caused interference with the climate system. The convention also aims to ensure ecosystems can adapt naturally, food production is not threatened, and economic development can proceed sustainably.
The Paris Agreement is the primary treaty produced under the UNFCCC framework, adopted at COP21 in Paris in 2015 and entering into force on the 4th of November 2016. It aims to limit the rise in global temperature to well below 2 degrees Celsius above pre-industrial levels, with an ambition of 1.5 degrees. It superseded the Kyoto Protocol, which had run from 2005 to 2020.
The principle, stated in Article 3(1), holds that all countries share responsibility for addressing climate change but developed nations are expected to take the lead because of their greater historical greenhouse gas emissions. Developing countries' commitments are also tied to whether developed countries deliver on financial resources and technology transfer.
By 2022, the UNFCCC had 198 parties, including all UN member states, the European Union, and a small number of non-member observers. The secretariat is based at the UN Campus in Bonn, Germany, and is currently led by Simon Stiell of Grenada, appointed Executive Secretary on the 15th of August 2022.
Critics point to the consensus-based voting system, which allows small groups of countries to block progress among more than 190 parties. The United States never ratified the Kyoto Protocol, Canada withdrew from it in 2011, and the United States announced its intention to withdraw from the UNFCCC entirely in January 2026. National Geographic noted before COP21 that twenty years of meetings had not moved the needle on carbon emissions.