The Paris Agreement on climate

The story

A planet that is heating up

When we burn coal, oil and gas to make electricity, move cars and heat homes, an invisible gas, carbon dioxide, ends up in the air. Together with other gases, it forms a sort of blanket around the Earth: it lets the Sun's light through but traps some of the heat. This is the “greenhouse effect”. Without it the Earth would be freezing; but if the blanket becomes too thick, the planet gets too hot.

Since industrialisation began, the amount of carbon dioxide in the air has risen by about a half, and the Earth's average temperature has gone up by about 1.2 degrees compared with the second half of the 19th century. It sounds like little, but a few degrees are enough to change the climate: glaciers melt, the sea rises, and heatwaves, droughts and floods become more frequent and stronger.

Scientists had known this for some time. In 1988 the United Nations had created a group of experts, the IPCC, to study the climate and report to governments. In 1992, in Rio de Janeiro, almost all countries signed a convention to protect the climate. In 1997 the Kyoto Protocol was signed, which set limits on emissions for rich countries but not for developing ones, and was only partly applied. In 2009 the Copenhagen conference ended without a real agreement.

In those years attention also grew among people who were not scientists. In June 2015, a few months before Paris, Pope Francis published the encyclical “Laudato si'”, a long letter about how to take care of our “common home” and about the link between the environment and justice for the poor, who are often the first to suffer from droughts and floods. That document was read by many non-believers too.

Two weeks in Paris

In December 2015, in Paris, in the Le Bourget area, representatives of 195 countries met for the twenty-first United Nations climate conference, COP21. It was chaired by the French foreign minister, Laurent Fabius, who for months had been travelling the world to find a compromise. After days of night-time negotiations, on 12 December the president of the conference brought his gavel down on the table: the Paris Agreement was approved, by consensus, by everyone present. Applause broke out in the hall.

The agreement set a common goal: to keep the rise in average temperature “well below 2 degrees” compared with pre-industrial times, and to do everything possible to stop at 1.5 degrees, the threshold beyond which the risks grow a great deal. This time every country, rich or poor, had to do its part, presenting its own plan, called a “nationally determined contribution”, and updating it every five years with ever more ambitious goals. Rich countries pledged to help poor ones with 100 billion dollars a year, to adapt to climate change and switch to clean energy.

On 22 April 2016, on Earth Day, more than a hundred and seventy countries signed the agreement at the United Nations in New York. The agreement came into force on 4 November 2016, much earlier than expected, because enough countries, responsible for over half of emissions, had ratified it.

Promises and facts

The United States, the second-largest emitter of greenhouse gases, announced in 2017 that it was leaving the agreement, then rejoined in 2021 and in 2025 announced its exit again. Many countries, from China to Europe, have chosen to reach “climate neutrality”, that is, to emit no more greenhouse gases than can be absorbed, by 2050 or 2060. In 2024, for the first time, the average temperature of a whole year exceeded the pre-industrial level by more than 1.5 degrees, according to the European Copernicus service.