Activists and politicians have cautiously welcomed an unexpected US-China declaration that vowed to boost climate cooperation.

The EU and UN described the move as encouraging and an important step, but Greenpeace said both countries needed to show more commitment.

The US and China are the world’s two biggest CO2 emitters.

They said they would work together to achieve the 1.5C temperature goal set out in the 2015 Paris Agreement.

Scientists say that limiting global temperature rises to 1.5C will help humanity avoid the worst climate impacts. This is compared with pre-industrial temperatures.

The announcement by the two global rivals was made on Wednesday at the COP26 climate summit in Glasgow, which officially ends 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 announcement was agreed upon following some 30 meetings over the past 10 months.

The reaction to the surprise agreement has been largely positive, but experts and activists have warned that concrete action must now be taken to support the promises.

Genevieve Maricle, director of US climate policy action at pressure group WWF, said the announcement offered “new hope” that the 1.5C limit might be achieved.