The draft “is not the decisive language that this moment requires,” said Aubrey Webson, president of the Alliance of Small Island States, a group of countries that are among those most threatened by climate change.
Scientists said nations need to cut global fossil fuel emissions roughly in the middle of this decade to prevent average global temperatures from rising above 1.5 degrees Celsius, or 2.7 degrees Fahrenheit, from pre-industrial levels. Beyond that threshold, the risks of deadly heat waves, droughts, forest fires, floods and species extinction increase considerably. The planet has already warmed by 1.1 degrees Celsius.
Negotiators here from nearly 200 countries are likely to request significant changes to the draft as the talks enter their final, more difficult stretch. Traditionally, a new global agreement requires all parties to join. If a nation objects, the talks can stall.
British Prime Minister Boris Johnson returned to Glasgow on Wednesday to urge countries to put aside differences and reach an agreement. “The world has heard the leaders of every country stand here and recognize the need for action,” he said. “And the world will find it utterly incomprehensible if we fail to deliver it.”
But persuading nations around the world, many of which depend on fossil fuels for energy and have their own internal policies and vested interests, to move in a new direction is a titanic challenge..
Mr. Kerry said countries have no choice but to work together. “This is not a discretionary thing,” he said. “This is science, it is mathematics and physics that dictate the path we must take. And we can’t achieve our goal if everyone doesn’t work together. “
Several experts said the joint pact between China and the US fell short of a 2014 agreement between the US and China to jointly reduce emissions, which helped spur the Paris climate deal between nearly 200 nations a year later.