Answer: a global agreement on the reduction of climate change
Explanation: COP21 Paris Climate Conference was the 2015 United Nations Climate Change Conference, that was held in Paris, France from 30 November to 12 December 2015. The Paris Agreement is an agreement within the United Nations Framework Convention on Climate Change, dealing with greenhouse-gas-emissions mitigation, adaptation, and finance, signed in 2016. As of February 2020, all UNFCCC members have signed the agreement, 189 have become party to it, and the only significant emitters which are not parties are Iran and Turkey.
The long-term temperature goal of this agreement is to keep the increase in global average temperature to well below 2 °C above pre-industrial levels and to pursue efforts to limit the increase to 1.5 °C, recognizing that this would substantially reduce the overall risks and impacts of climate change.