Paris Agreement (2015): The Global Climate Deal Agreed at COP21

The Paris Agreement is the international treaty on climate change adopted by 196 parties at the COP21 conference near Paris on 12 December 2015. It commits countries to hold the rise in global average temperature “well below 2°C” above pre-industrial levels and to pursue efforts to limit it to 1.5°C, mainly through national climate plans that are reviewed and strengthened every five years. The first climate deal to include almost every nation, it remains the central framework of global climate policy, although progress has fallen short of its goals.

Background: from Rio to Paris

Scientific concern about global warming caused by greenhouse gases grew through the 1980s, leading to the founding of the IPCC in 1988. At the Earth Summit in Rio de Janeiro in 1992, countries adopted the UN Framework Convention on Climate Change (UNFCCC), whose members meet each year at a Conference of the Parties (COP).

The Kyoto Protocol of 1997 set legally binding emissions targets, but only for developed countries. The United States never ratified it, and fast-growing emitters such as China and India had no obligations. Efforts to agree a broader successor collapsed at the Copenhagen climate summit of 2009, which ended in acrimony with only a short political accord. Negotiators then changed approach: at Durban in 2011 they agreed to produce, by 2015, a new agreement applicable to all countries.

The new approach was “bottom-up”. Instead of negotiating targets centrally, each country would put forward its own plan, called an intended nationally determined contribution, before the conference. By the time COP21 opened, more than 180 countries had done so.

A key moment came in November 2014, when US President Barack Obama and Chinese President Xi Jinping, leaders of the world’s two biggest emitters, jointly announced their climate targets in Beijing. Christiana Figueres, the Costa Rican diplomat who led the UNFCCC secretariat, and the French government under President François Hollande and Foreign Minister Laurent Fabius spent months on preparatory diplomacy. The 2015 papal encyclical Laudato si’ and growing evidence of climate impacts added to public pressure.

COP21 and the final deal

COP21 opened at Le Bourget, north of Paris, on 30 November 2015, just over two weeks after the terrorist attacks in the city that killed 130 people; security was tight and planned street marches were banned. About 150 heads of state and government attended the opening day.

The two weeks of talks centred on several disputes: whether the goal should be 2°C or 1.5°C, how to share obligations between rich and poor countries, money for developing nations, and how legally binding the deal should be. Small island states and the least developed countries, facing rising seas, pressed hard for 1.5°C, and a “High Ambition Coalition” that included the Marshall Islands, the European Union and later the United States helped win its inclusion.

The talks ran a day beyond schedule. On the final day a last-minute problem arose when the draft said developed countries “shall” undertake economy-wide emissions targets, wording the US delegation said would require approval by the Senate; it was corrected to “should” as a technical error. On the evening of 12 December 2015 Fabius, presiding, brought down his green gavel to declare the agreement adopted, to a standing ovation.

What the agreement says

Article 2 sets the temperature goal: holding warming “well below 2°C” and pursuing efforts to limit it to 1.5°C. Article 4 aims for global emissions to peak as soon as possible and for a balance between emissions and removals of greenhouse gases, effectively net zero, in the second half of the century.

Every party must prepare, communicate and maintain successive nationally determined contributions (NDCs), each expected to be more ambitious than the last, and submit new ones every five years. An “enhanced transparency framework” requires countries to report on their emissions and progress, and a “global stocktake” every five years, the first concluded in 2023, assesses collective progress. Other articles cover adaptation to climate impacts, “loss and damage” from extreme weather and sea-level rise, cooperation through carbon markets, and finance.

The agreement itself does not set numerical finance figures, but the accompanying decision kept developed countries’ pledge to mobilise 100 billion US dollars a year for developing countries and called for a higher goal to be set before 2025. In 2024 the Baku conference agreed a new target of at least 300 billion dollars a year by 2035.

Key people

Laurent Fabius, France’s foreign minister, presided over COP21 and steered the final days of bargaining, using small “confessional” meetings with individual delegations and an informal process known as the indaba, borrowed from South African practice, in which ministers set out their red lines face to face. Christiana Figueres, executive secretary of the UNFCCC from 2010 to 2016, is widely credited with rebuilding trust after Copenhagen and with persuading governments that a deal was possible.

UN Secretary-General Ban Ki-moon made climate change a priority of his second term and convened a climate summit in New York in 2014. Barack Obama and Xi Jinping gave the process political momentum, while India’s Prime Minister Narendra Modi insisted on recognition of “climate justice” and the right of poorer countries to develop. Laurence Tubiana, France’s chief climate negotiator, and Tony de Brum, foreign minister of the Marshall Islands and a driving force of the High Ambition Coalition, also played leading roles.

Signature and entry into force

On 22 April 2016, Earth Day, 175 parties signed the agreement at the United Nations in New York, the largest number ever to sign an international agreement on a single day. The United States and China formally joined together on 3 September 2016 in Hangzhou. Once at least 55 parties responsible for at least 55 per cent of global emissions had ratified, the treaty entered into force on 4 November 2016, far faster than expected.

Detailed rules, the “Paris Rulebook”, were largely agreed at Katowice, Poland, in 2018, with the final pieces on carbon markets settled at Glasgow in 2021 and Baku in 2024. In 2018 the IPCC, invited by the parties, published a special report showing that limiting warming to 1.5°C rather than 2°C would substantially reduce risks such as heatwaves, coral reef loss and sea-level rise.

The United States: exit and return

On 1 June 2017 President Donald Trump announced that the United States would withdraw, arguing that the agreement disadvantaged American workers and businesses. Under the treaty’s rules, the withdrawal could only take effect on 4 November 2020. Many US states, cities and companies pledged to keep pursuing its goals in the meantime.

President Joe Biden signed an order to rejoin on his first day in office, 20 January 2021, and the United States became a party again on 19 February 2021. On 20 January 2025, at the start of his second term, Trump ordered a second withdrawal, which took effect a year after formal notification, in January 2026. No other country followed the United States out.

The record so far

Supporters argue that the agreement has bent the curve of expected warming. Before Paris, projections commonly pointed to around 3.5-4°C by 2100; UN assessments in 2023-2024 estimated that policies then in place implied roughly 2.6-3.1°C. More than 140 countries have announced net-zero targets, and the rapid fall in the cost of solar power, wind power and batteries has accelerated the shift to clean energy.

Critics note that global emissions continued to rise for most of the decade after 2015, that many national pledges are not backed by policies, and that the agreement has no means of enforcement. 2024 was the first calendar year in which the global average temperature was about 1.5°C above pre-industrial levels, according to the World Meteorological Organization, although the Paris goal refers to longer-term averages over about two decades. Disputes over finance and over phasing out fossil fuels remain at the heart of every annual COP.

The agreement’s main figures are summarised below.

Timeline

• 1992, June: The UN Framework Convention on Climate Change is adopted at the Rio Earth Summit.
• 2009, December: The Copenhagen summit fails to agree a new binding treaty.
• 2014, November: The United States and China announce joint climate targets.
• 2015, 30 November: COP21 opens at Le Bourget near Paris.
• 2015, 12 December: The Paris Agreement is adopted.
• 2016, 22 April: 175 parties sign the agreement in New York.
• 2016, 4 November: The agreement enters into force.
• 2020, 4 November: The first US withdrawal takes effect.
• 2021, 19 February: The United States rejoins.
• 2023, December: The first global stocktake is concluded at COP28 in Dubai.

Why it matters

The Paris Agreement is the first truly global climate treaty, uniting rich and poor countries behind a shared temperature goal and a regular cycle of rising ambition. Its success depends on whether national pledges are strengthened and carried out, which makes it one of the most closely watched agreements of the twenty-first century.