European Commission president Ursula von der Leyen summed up the sentiment of many at the global climate summit: "It is so good to have the US back on our side in the fight against climate change. Together we can go faster and get further, and together we will win the future."
Optimism stemmed from a stepped-up emissions goal announced by the host, Joe Biden, that provided a tangible break from the climate denialist presidency of Donald Trump. Declaring the US will halve its emissions by 2030 based on 2005 levels unmistakably indicates the US is back in the Paris Agreement fold.
For Biden’s home audience, there was a promise of millions of jobs and a stronger middle class though many Republicans warn it will damage an economy which remains heavily reliant on fossil fuels.
On the international front, much will hinge upon co-operation between China and US. This is running on a smoother track of late – compared to tensions on trade and human rights – thanks to diplomatic efforts of Biden's climate envoy John Kerry.
The US president has already provided indication of intent. He has announced a $2 trillion infrastructure programme hinged on clean energy. He is backing efforts to integrate climate-related risk into the financial system.
Existential risk
US treasury secretary Janet Yellen recently underlined the currently accepted reality; climate change had become an "existential risk to our future economy and way of life", she said, vowing to try to catalyse public investments in green energy and private financing of green technologies.
UN secretary general António Guterres set out key steps needing firming up in advance of the Cop26 gathering in November that will test the commitment of all, including big emitters such as Russia, India and Saudi Arabia.
They range across pricing carbon, “shifting taxation from income to carbon”; ending fossil fuel subsidies and ramping up investments in renewable energy and green infrastructure.
“Stop the financing of coal and the building of new coal power plants. Phase out coal by 2030 in the wealthiest countries, and by 2040 everywhere else,” he advised – an immediate challenge to China and the US.
Guterres is demanding a breakthrough on climate finance and adaptation which is critical for trust and collective action. His call for concrete proposals that ease access to finance and technological support for vulnerable countries needs to be delivered on urgently.
Wealthy countries, especially in the global north, are still in the dock given past failures on mitigation, on helping those developing countries experiencing severe climate disruption, and on meeting Paris targets – when climate science is indicating ambition and delivery needs to be racheted up even further.