The Paris Agreement was opened for signature on 22 April 2016 (Earth Day) at a ceremony in New York. After several European Union states ratified the agreement in October 2016, there were enough countries that had ratified the agreement that produce enough of the world's greenhouse gases for the agreement to enter into force. The agreement went into effect on 4 November 2016.
Within the United Nations Framework Convention on Climate Change, legal instruments may be adopted to reach the goals of the convention. For the period from 2008 to 2012, greenhouse gas reduction measures were agreed in the Kyoto Protocol in 1997. The scope of the protocol was extended until 2020 with the Doha Amendment to that protocol in 2012.
During the 2011 United Nations Climate Change Conference, the Durban Platform (and the Ad Hoc Working Group on the Durban Platform for Enhanced Action) was established with the aim to negotiate a legal instrument governing climate change mitigation measures from 2020. The resulting agreement was to be adopted in 2015.
At the conclusion of COP 21 (the 21st meeting of the Conference of the Parties, which guides the Conference), on 12 December 2015, the final wording of the Paris Agreement was adopted by consensus by all of the 195 UNFCCC participating member states and the European Union to reduce emissions as part of the method for reducing greenhouse gas. In the 12-page Agreement, the members promised to reduce their carbon output "as soon as possible" and to do their best to keep global warming "to well below 2 °C" [3.6 °F].
The Paris Agreement was open for signature by states and regional economic integration organizations that are parties to the UNFCCC (the Convention) from 22 April 2016 to 21 April 2017 at the UN Headquarters in New York.
The agreement stated that it would enter into force (and thus become fully effective) only if 55 countries that produce at least 55% of the world's greenhouse gas emissions (according to a list produced in 2015) ratify, accept, approve or accede to the agreement. On 1 April 2016, the United States and China, which together represent almost 40% of global emissions, issued a joint statement confirming that both countries would sign the Paris Climate Agreement. 175 Parties (174 states and the European Union) signed the agreement on the first date it was open for signature. On the same day, more than 20 countries issued a statement of their intent to join as soon as possible with a view to joining in 2016. With ratification by the European Union, the Agreement obtained enough parties to enter into effect as of 4 November 2016.
Both the EU and its member states are individually responsible for ratifying the Paris Agreement. A strong preference was reported that the EU and its 28 member states deposit their instruments of ratification at the same time to ensure that neither the EU nor its member states engage themselves to fulfilling obligations that strictly belong to the other, and there were fears that disagreement over each individual member state's share of the EU-wide reduction target, as well as Britain's vote to leave the EU might delay the Paris pact. However, the European Parliament approved ratification of the Paris Agreement on 4 October 2016, and the EU deposited its instruments of ratification on 5 October 2016, along with several individual EU member states.
The process of translating the Paris Agreement into national agendas and implementation has started. One example is the commitment of the least developed countries (LDCs). The LDC Renewable Energy and Energy Efficiency Initiative for Sustainable Development, known as LDC REEEI, is set to bring sustainable, clean energy to millions of energy-starved people in LDCs, facilitating improved energy access, the creation of jobs and contributing to the achievement of the Sustainable Development Goals.
Per analysis from the Intergovernmental Panel on Climate Change (IPCC) a carbon "budget" based upon total carbon dioxide emissions in the atmosphere (versus the rate of annual emission) to limit global warming to 1.5 °C was estimated to be 2.25 trillion tonnes of overall emitted carbon dioxide from the period since 1870. This number is a notable increase from the number estimated by the original Paris Climate accord estimates (of around 2 trillion tonnes total) total carbon emission limit to meet the 1.5 °C global warming target, a target that would be met in the year 2020 at 2017 rates of emission.[clarification needed] Additionally, the annual emission of carbon is estimated in 2017 to be at 40 billion tonnes emitted per year. The revised IPCC budget for this was based upon CMIP5 climate model. Estimate models using different base-years also provide other slightly adjusted estimates of a carbon "budget".
In July 2020 the World Meteorological Organisation (WMO) announced that it assessed a 20% chance of global warming compared to pre-industrial levels exceeding 1.5 °C in at least one year between 2020 and 2024, with 1.5 °C being a key threshold under the Paris Agreement.
In December 2020, the former chair of the COP 21, Laurent Fabius, argued that the implementation of the Paris Agreement could be bolstered by the adoption of a Global Pact for the Environment. The latter would define the environmental rights and duties of States, individuals and businesses. This project is currently under discussion at the United Nations.
As of November 2020, 194 states and the European Union have signed the Agreement. 187 states and the EU, representing about 79% of global greenhouse gas emissions, have ratified or acceded to the Agreement, including China and India, the countries with the 1st and 3rd largest CO2 emissions among UNFCC members. As of January 2021[update] greenhouse gas emissions by Iran and greenhouse gas emissions by Turkey are both over 1% of the world total. Eritrea, Iraq, South Sudan, Libya and Yemen are the only other countries which have never ratified the agreement.
Article 28 of the agreement enables parties to withdraw from the agreement after sending a withdrawal notification to the depositary. Notice can be given no earlier than three years after the agreement goes into force for the country. Withdrawal is effective one year after the depositary is notified. Alternatively, the Agreement stipulates that withdrawal from the UNFCCC, under which the Paris Agreement was adopted, would also withdraw the state from the Paris Agreement. The conditions for withdrawal from the UNFCCC are the same as for the Paris Agreement. The agreement does not specify provisions for non-compliance.
On August 4, 2017, the Trump administration delivered an official notice to the United Nations that the U.S. intended to withdraw from the Paris Agreement as soon as it was legally eligible to do so. The formal notice of withdrawal could not be submitted until the agreement was in force for three years for the US, on November 4, 2019. On November 4, 2019, the US government deposited the withdrawal notification with the Secretary General of the United Nations, the depositary of the agreement, and officially withdrew from the Paris climate accord one year later when the withdrawal became effective.
Joe Biden, who defeated Donald Trump in the 2020 presidential election, signed an executive order on his first day in office, January 20, 2021, to re-admit the United States into the Paris Agreement. Following the 30-day period set by Article 21.3, the US was readmitted to the Agreement on February 19, 2021. United State Climate Envoy John Kerry took part in virtual events, saying that the US would "earn its way back" into legitimacy in the Paris process. United Nations Secretary-General António Guterres welcomed the return of the United States as restoring the “missing link that weakened the whole".
A "National Communication" is a type of report submitted by the countries that have ratified the United Nations Framework Convention on Climate Change (UNFCCC). Developed countries are required to submit National Communications every four years and developing countries should do so. Some Least Developed Countries have not submitted National Communications in the past 5–15 years, largely due to capacity constraints.
National Communication reports are often several hundred pages long and cover a country's measures to mitigate greenhouse gas emissions as well as a description of its vulnerabilities and impacts from climate change. National Communications are prepared according to guidelines that have been agreed by the Conference of the Parties to the UNFCCC. The (Intended) Nationally Determined Contributions (NDCs) that form the basis of the Paris Agreement are shorter and less detailed but also follow a standardized structure and are subject to technical review by experts.
While the United States and Turkey are not part of the agreement, since the countries have not declared an intention to withdraw from the 1992 UNFCCC, as "Annex 1" countries under the UNFCCC they will continue to be obliged to prepare National Communications and an annual greenhouse gas inventory.
A pair of studies in Nature have said that, as of 2017, none of the major industrialized nations were implementing the policies they had envisioned and they have not met their pledged emission reduction targets, and even if they had, the sum of all member pledges (as of 2016) would not keep global temperature rise "well below 2 °C".
How well each individual country is on track to achieving its Paris agreement commitments can be continuously followed on-line (through the Climate Change Performance Index, Climate Action Tracker and the Climate Clock).
A 2018 published study points at a threshold at which temperatures could rise to 4 or 5 degrees (ambiguous phrase, continuity would be “4-5 °C”) compared to the pre-industrial levels, through self-reinforcing feedbacks in the climate system, suggesting this threshold is below the 2-degree temperature target, agreed upon by the Paris climate deal. Study author Katherine Richardson stresses, "We note that the Earth has never in its history had a quasi-stable state that is around 2 °C warmer than the pre-industrial and suggest that there is substantial risk that the system, itself, will 'want' to continue warming because of all of these other processes – even if we stop emissions. This implies not only reducing emissions but much more."
At the same time, another 2018 published study notes that even at a 1.5 °C level of warming, important increases in the occurrence of high river flows would be expected in India, South and Southeast Asia. Yet, the same study points out that with 2 °C of warming various areas in South America, central Africa, western Europe, and the Mississippi area in the United States would see more high flows; thus increasing flood risks.
Although the agreement was lauded by many, including French President François Hollande and UN Secretary General Ban Ki-moon, criticism has also surfaced. For example, James Hansen, a former NASA scientist and a climate change expert, voiced anger that most of the agreement consists of "promises" or aims and not firm commitments. He called the Paris talks a fraud with 'no action, just promises' and feels that only an across the board tax on CO2 emissions, something not part of the Paris Agreement, would force CO2 emissions down fast enough to avoid the worst effects of global warming.
Institutional asset owners associations and think-tanks have also observed that the stated objectives of the Paris Agreement are implicitly "predicated upon an assumption – that member states of the United Nations, including high polluters such as China, the US, India, Russia, Japan, Germany, South Korea, Iran, Saudi Arabia, Canada, Indonesia and Mexico, which generate more than half the world's greenhouse gas emissions, will somehow drive down their carbon pollution voluntarily and assiduously without any binding enforcement mechanism to measure and control CO2 emissions at any level from factory to state, and without any specific penalty gradation or fiscal pressure (for example a carbon tax) to discourage bad behaviour." Emissions taxes (such as a carbon tax) can be integrated into the country's NDC however.
According to the United Nations Environment Programme (UNEP), if only the current climate commitments of the Paris Agreement are relied upon, temperatures will likely have risen by 3.2 °C by the end of the 21st century. To limit global temperature rise to 1.5 °C, annual emissions must be below 25 gigatons (Gt) by 2030. With current Nov 2019 commitments, emissions will be 56 Gt CO2e by 2030, twice the environmental target. To limit global temperature rise to 1.5 °C, the global annual emission reduction needed is 7.6% emissions reduction every year between 2020 and 2030. The top four emitters (China, USA, EU27 and India) contributed to over 55% of the total emissions over the last decade,[clarification needed] excluding emissions from land-use change such as deforestation. China's emissions grew 1.6% in 2018 to reach a high of 13.7 Gt of CO2 equivalent. The US emits 13% of global emissions and emissions rose 2.5% in 2018. The EU emits 8.5% of global emissions has declined 1% per year across the last decade. Emissions declined 1.3% in 2018. India's 7% of global emissions grew 5.5% in 2018 but its emissions per capita is one of the lowest within the G20.