It was an agreement born from a fear of failure, delivered by the smoothness of French diplomacy.
Six years earlier, countries had bitterly walked away from global climate talks in Copenhagen without a deal. The decision to reassemble in Paris to try again at getting almost 200 countries to sign a pact on cutting carbon emissions was a gamble: another collapse could the end world's ability to forge a common approach to dealing with climate change.
And no political leader wanted his reputation stained by a repeat of the debacle in Copenhagen.