World leaders gather at the United Nations on Friday to sign the Paris climate deal and get the ball rolling on a quick entry into force to start beating back global warming.
French President Francois Hollande and Canada's Justin Trudeau will join US Secretary of State John Kerry for the ceremony attended by more than 165 governments, the largest ever one-day signing of an international agreement.
Held on Earth Day, the ceremony comes four months after the hard-won deal was clinched in Paris and marks the first step toward binding countries to the promises they made to cut greenhouse gas emissions.
Oscar winner and environmental activist Leonardo DiCaprio will be on hand to praise leaders for signing, urge others to do the same and appeal to all to turn their commitments into action.
While the United States, China and India—the world's top greenhouse gas emitters - will not be represented at their highest level, there will be some 60 heads of state and government on hand for the signing.
Among those will be leaders of island states such as Fiji, Tuvalu and Kiribati that face oblivion from rising sea levels. They will formally present the already-completed ratification by their parliaments.
Moving quickly, 13 countries have so far ratified the agreement, but for many of the signatories, final approval of the Paris deal could drag on and involve new legislation to parliaments.
Still, there is no time to lose.
Fast-track climate action
Last month was the hottest March in modern history and 2016 is shaping up as a record-breaking year for rising global temperatures.
This year's El Nino—dubbed "Darth Nino"—is wreaking havoc, with droughts, floods, severe storms and other extreme weather patterns.
The Paris agreement will come into force as soon as 55 countries responsible for 55 percent of the world's greenhouse gases have ratified the accord.
The target date for the agreement to begin is 2020.
China and the United States have said they will ratify this year and are pushing for quick ratification so that the agreement becomes operational possibly as early as late 2016 or 2017.
Caught in election-year turmoil, the United States plans to ratify the Paris accord with an executive agreement, bypassing Congress and setting up a complex process for any future president wishing to pull out.
The European Union's 28 countries are expected to take up to about a year and a half, said EU vice president Maros Sefcovic, who will be signing on behalf of the EU.
"We definitely want to be in the first wave," he said.
"Early ratification and entry into force will send a strong signal to governments, businesses and communities that it is time to fast-track climate action," UN Secretary-General Ban Ki-moon said earlier this mont.
He said the real challenge can be summed up in one word: "implementation."
Agreed by 195 nations, the Paris deal sets the goal of limiting global warming to 2 degrees Celsius above pre-industrial levels by moving to clean energy.
It also places an onus on rich nations to help poorer ones make the transition to a low-carbon economy.
The deal was seen as a triumph for Ban who pushed for the deal throughout his tenure and has listed the agreement in Paris as one of his proudest moments as UN chief.
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