Much will hinge upon cooperation between China, the world’s worst producer of planet-heating emissions, and the US, historically the worst polluter. On Saturday, John Kerry, Biden’s climate envoy, struck an agreement in Shanghai to urgently address what Kerry called the “beyond catastrophic” consequences of allowing temperatures to spiral upwards. The compact is broadly seen as encouraging but comes amid US-China tensions on issues including human rights and trade. The US also faces a deficit in credibility after the presidency of Donald Trump, which saw the country leave the Paris climate accords and dismantle environmental protections. Biden has returned the US to the Paris agreement but a spokesman for the Chinese foreign ministry said the move was “by no means a glorious comeback but rather the student playing truant getting back to class”.