US President Barack Obama looks on as Chinese President Xi Jinping speaks during a joint press conference in the Great Hall of the People in Beijing Photograph: Greg Baker/AFP/Getty Images
Barack Obama aims for reduction of a quarter or more by 2025, while Xi Jinping sets goal for emissions to fall after 2030
The United States and China have unveiled a secretly negotiated deal to reduce their greenhouse gas output, with China agreeing to cap emissions for the first time and the US committing to deep reductions by 2025.
The pledges in an agreement struck between President Barack Obama and his Chinese counterpart, Xi Jingping, provide an important boost to international efforts to reach a global deal on reducing emissions beyond 2020 at a United Nations meeting in Paris next year.
China, the biggest emitter of greenhouse gases in the world, has agreed to cap its output by 2030 or earlier if possible. Previously China had only ever pledged to reduce the rapid rate of growth in its emissions. Now it has also promised to increase its use of energy from zero-emission sources to 20% by 2030.
The United States has pledged to cut its emissions to 26-28% below 2005 levels by 2025.