Efforts to build a new global deal to tackle climate change were for many years criticised for moving at a glacial pace. But this week climate negotiators meeting in Morocco find themselves facing an entirely new problem: a deal that, astonishingly, has come into effect more than three years ahead of schedule.
The Paris Agreement on climate change, designed to start in 2020, entered into force on Friday, a month after reaching key ratification thresholds. On Sunday, the United Nations said 100 parties - 99 countries and the European Union - had formally joined the accord.
Australia is yet to ratify the deal but says it hopes to do so by the end of the year.
The swift movement of the deal in coming into force has been a cause for celebration - and some puzzlement.
"We're now in an interesting conundrum we never thought we'd find ourselves in: After pushing for decisive and speedy action, we got it," said Paula Caballero, global director of the climate programme at the Washington-based World Resources Institute (WRI).
The immediate challenge for negotiators is that, by law, countries that have ratified the deal must start agreeing the rules to implement it at the next UN climate conference.
But that meeting starts on Monday in Marrakesh. That has left officials a very short time to iron out a host of technical issues - and only about half the parties that crafted the Paris deal eligible to participate in the early decision-making.
"Because we've jump-started the [deal], we now have to find a way for negotiators to discuss the rules while still finding ways for other countries to come in and join," said Liz Gallagher, a climate diplomacy expert at London-based E3G, a sustainable-development think tank.
Many nations also have an anxious eye on this week's US elections, where Republican presidential candidate Donald Trump has promised to pull his country out of the climate agreement if elected.
That threat, in recent months, has spurred a rush to ratify the agreement and ensure it takes force before the US vote.
Under the rules of the Paris Agreement, once it has come into effect, "legally a country cannot withdraw before the next five years are over", said Sven Harmeling, international climate change policy coordinator for the aid agency CARE.