U.N. Secretary-General Ban Ki-moon has been campaigning for global action on climate change since he took office on Jan. 1, 2007. He was on stage Dec. 12 in Paris when nearly 200 countries adopted an agreement.
Some key moments on the secretary-general's road to Paris:
September 2007 — Ban calls a high-level U.N. meeting on climate change. He goes to Washington and tells then-President George W. Bush that the summit's success depends on his participation. Bush attends but does not speak.
November 2007 — The secretary-general visits Antarctica to see melting ice, Chile to view receding glaciers and the Amazon to highlight deforestation.
December 2007 — Delegates from nearly 190 nations meeting in Bali, Indonesia, agree to adopt a blueprint for fighting global warming by 2009
December 2009 — A major U.N. climate conference in Copenhagen ends without a legally binding agreement to combat global warming.
December 2010 — Ban presents a U.N. conference in Cancun, Mexico with ideas from international political and financial leaders. The conference adopts a modest climate deal creating a fund to help the developing world go green.
September 2014 — Ban hosts a summit on climate change at U.N. headquarters where President Barack Obama and other world leaders stress the urgency of addressing global warming. But many obstacles remain.
December 2014 — A last-minute deal salvages U.N. climate talks in Lima, Peru and sends a signal that it's possible to overcome a divide between rich and poor nations on how much each should provide to combat global warming. Ban urges big carbon polluters to follow the examples of China, the U.S. and the European Union and announce targets to reduce emissions.
November 2015 — Ban says key issues remaining ahead of the major climate summit in Paris in December are too challenging for negotiators and that world leaders must step in.
December 12, 2015 — Nearly 200 countries reach an agreement that requires all countries — not just wealthy nations — to reduce their greenhouse gas emissions. Its aim is to keep global temperatures from rising another degree Celsius (1.8 Fahrenheit) between now and 2100, a key demand of poor countries ravaged by rising sea levels and other effects of climate change.
December 14, 2015 — Ban invites world leaders to the United Nations on April 22, 2016 — Earth Day — to sign the landmark agreement to tackle climate change that was reached in Paris, the first step toward ratification.