The Paris Agreement is a treaty signed by 196 member nations of the United Nations Framework Convention on Climate Change (UNFCCC) in an effort to reduce greenhouse-gas (GHG) emissions, primarily of carbon dioxide and methane, thereby limiting the effects of climate change to the greatest extent possible, with the longer-term goal of reaching net-zero emissions of greenhouse gases. The accord, based on voluntary reductions of GHG emissions by member nations, was reached on December 12, 2015 and went into force on November 4, 2016. The United States withdrew from the Paris Agreement on November 4, 2020, and rejoined on February 19, 2021. See also: Carbon dioxide; Global climate change; Greenhouse effect; Methane
The goal of the Paris Agreement is to keep global warming below 2 degrees Celsius, relative to pre-industrial average global temperatures. That amount of warming will still cause considerable climate impact, including coastal flooding from sea-level rise, increased air pollution, extreme weather events, shortfalls in freshwater supplies and food production, damage to ecosystems, loss of habitats, and so on. To limit the temperature increase, participating nations have submitted plans (pledges), called nationally determined contributions (NDCs), which set forth objectives and policies for reducing GHG emissions. The NDCs are voluntary and can be revised (strengthened or weakened) at any time without penalty. See also: Air pollution; Deforestation; Extreme weather events; Global warming; Sea-level rise
To reduce GHG emissions, participants will have to rely less on fossil fuels and adopt green energy sources, such as solar and wind power. At the same time, the Paris Agreement urges nations to implement conservation and carbon sequestration (sink) efforts, such as growing forests. Current NDC pledges, however, are not expected to keep the global average temperature from rising above the goal of 2 degrees Celsius. As a result, a five-year review cycle was established to assess overall progress and to commit to more aggressive goals in the future. The first review under the agreement will take place in 2023. See also: Fossil fuel; Solar energy; Wind power
To help developing nations mitigate and adapt to the effects of climate change as well as to adopt technology for reducing GHG emissions, the Green Climate Fund was established. To date, five countries, three regions, and one city (Paris, France) have pledged U.S. $10 billion to the Green Climate Fund.