The Paris Agreement is a treaty signed by 195 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 after extensive negotiations. By June 2017, a total of 148 (about 75%) UNFCCC members had ratified the agreement, with only one nation, the United States, pulling out. See also: Atmosphere; Carbon dioxide; Climate modification; Climatology; 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. Emission reductions will begin in 2020. See also: Adaptive responses in animals to climate change; Air pollution; Deforestation; Disease outbreaks in livestock due to global warming; Extreme weather events; Effects of global warming on polar bears; Global climate change affects Arctic treeline; Global warming; Hydrological consequences of global warming; Modeling effects of climate change on allergic illness; Plant vulnerability to climate change; Tornado activity and climate change; Tree seasonality in a warming climate; Species and global climate change
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: Carbon capture and storage; Fossil fuel; Potential of soils for carbon sequestration; 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. Initially, about $10 billion was pledged by wealthier nations, knowing more funding would be needed. The United States had pledged $3 billion and would have been a major contributor if it had fulfilled its commitment, even though on a per capita (person) basis it was not a top contributor. The level of funding was one of the reasons cited for the U.S. pullout. However, that reasoning has been questioned because total European Union (excluding the United Kingdom) pledges exceed $3 billion, as does the sum of Japan’s and the United Kingdom’s pledges.
It is too early to say how the United States’ withdrawal from the Paris Agreement will impact its outcome. For certain, the accord will not be renegotiated and it will be harder to slow the rise of global temperature.