Agreement was reached on 14 December in Paris by the 195 countries attending the 21st conference of the parties (COP21) to the United Nations Framework Convention on Climate Change (UNFCCC), which began on 30 November.

The objective is to keep global temperature increases this century well below 2 degrees Celsius, and drive efforts to limit temperature increases to below 1.5 degrees Celsius, which UNFCCC says is a "significantly safer" defence against the worst impacts of climate change.

The agreement supports mitigation efforts to reduce carbon emissions in order to achieve the temperature goal and also seeks to strengthen the ability of countries to deal with climate change impacts. It provides for a transparency system to account for actions taken, and puts into place a mechanism for support – including financial support – to help countries to reach their goals.

The European Commission (EC) said the deal is the culmination of years of efforts by the international community to bring about a universal multilateral agreement on climate change. Following limited participation in the Kyoto Protocol and the lack of agreement in Copenhagen in 2009, a broad coalition of developed and developing countries "sends a clear signal to investors, businesses, and policy-makers that the global transition to clean energy is here to stay and resources have to shift away from polluting fossil fuels".

Under the Paris agreement, countries will submit updated climate plans called nationally determined contributions (NDCs) every five years. Future national plans will be required to be no less ambitious than existing ones, meaning that the INDCs have in effect become a foundation for more ambitious action in future. The agreement acknowledges "the need to promote universal access to sustainable energy in developing countries, in particular in Africa, through the enhanced deployment of renewable energy", but does not mention nuclear power.

The International Energy Agency (IEA) said the agreement is "nothing less than a historic milestone for the global energy sector" that would "speed up the transformation of the energy sector by accelerating investments in cleaner technologies and energy efficiency".

During the conference discussions, International Atomic Energy Agency deputy director-general Mikhail Chudakov said nuclear energy is a "clean, reliable, affordable and modern energy source" that should be considered among low carbon options and as an important contributor to a sustainable energy future. He told a side event that nuclear energy has low life-cycle greenhouse gas emissions and has the potential, with innovative technologies, to serve humanity effectively for a very long time. He also said that in developing economies more effective use should be made of technologies such as small and medium reactors. "When considered in the broader context of sustainable development, nuclear power enhances energy security and reduces damage to ecosystems and impact on human health," he said.