The UN says 97 parties have now ratified the convention
The Paris Agreement on Climate Change Agreement has come into force.
The document was adopted in Paris back in December 2015.
It required at least 55 parties, accounting for at least 55% of global greenhouse gas emissions, to take effect.
The UN Framework Convention on Climate Change (UNFCCC) says 97 parties have now ratified the convention.
This includes the biggest and smallest emitters, the richest and the most vulnerable nations. Ireland became a signatory on April 22nd.
Its central aim is to strengthen the global response to the threat of climate change by keeping a global temperature rise below 2 degrees Celsius above pre-industrial levels.
It will also pursue efforts to limit the temperature increase even further to 1.5 degrees Celsius.
Another key issue is to ensure that the US$100bn (€89.7bn), pledged by developed countries to developing ones, is building in the run up to 2020 - and that even larger sums are being leveraged from investors, banks and the private sector that can build towards the US$5 to US$7tn (€4.48 to €6.28tn) needed to support a world-wide transformation.
"This is a truly historic moment for people everywhere. The two key thresholds needed for the Paris Climate Change Agreement to become legal reality have now been met," said Patricia Espinosa, executive secretary of the UNFCCC.
"The speed at which countries have made the Paris’s Agreement’s entry into force possible is unprecedented in recent experience of international agreements and is a powerful confirmation of the importance nations attach to combating climate change and realizing the multitude of opportunities inherent in the Paris Agreement".
The UN Secretary-General Ban Ki-moon said: "Strong international support for the Paris Agreement entering into force is testament to the urgency for action, and reflects the consensus of governments that robust global cooperation is essential to meet the climate challenge."
Its ratification came only days before the start of this year's UN Climate Change Conference in Marrakech.
The Paris Agreement can be read in full here