Activists and politicians cautiously welcomed an unexpected US-China declaration that promised to strengthen climate cooperation.
The EU and the UN described the movement as encouraging and an important step, but Greenpeace said both countries needed to take concrete action.
The USA and China are the two largest CO2 emitters in the world.They said they would work together to reach the 1.5C temperature target set in the 2015 Paris Agreement.
Scientists say limiting global temperature rise to 1.5C will help humanity avoid the worst climate effects. This is compared with pre-industrial temperatures.
While the latest promise is brief in detail, analysts say it is a tacit recognition by China that the crisis warrants urgent attention and that it will play a greater role in facing the global challenge.
The announcement of the two global rivals was made on Wednesday at the COP26 climate summit in Glasgow, which officially closes on Friday.
US President Joe Biden and his Chinese counterpart Xi Jinping are now expected to hold a virtual meeting as early as next week.
According to China’s climate envoy, the declaration was reached after 30 meetings with the US in the last 10 months.
It is committed to working closely together to reduce emissions, while a joint working group will also “meet regularly to address the climate crisis” over the coming decades.
The reaction to the surprise agreement was largely positive, but experts and activists have warned that policies must now be put in place to support the promises.
Genevieve Maricle, director of U.S. climate policy action at the WWF pressure group, said the announcement offers “new hope” that the 1.5C limit can be reached.
But she added that “we also need to be clear about what is still required if the two countries are to deliver the necessary emission reductions over the next nine years”.
Greenpeace International executive director Jennifer Morgan has warned that China and the United States need to show more commitment to achieving climate change.
Former Australian Prime Minister Kevin Rudd, president of the Asia Society, which works on the Global Climate Change Agreement, told the BBC that the agreement was “not a game changer” but was a big step forward.
“The current state of geopolitics between China and the United States is appalling, so the fact that you are extracting this … agreement between Washington and Beijing right now is [important],” he said.