There is much work to do but President Biden’s leadership will be of profound importance.
Just days after the US left the global Paris deal on climate change, Americans have elected a president who has promised to tackle the “existential threat” rising temperatures pose.
Joe Biden’s climate plan for the US, which as the world’s second largest polluter accounts for 15 percent of global greenhouse gas emissions, includes a goal to reach “net zero” emissions by 2050.
That would bring the US in line with countries such as the UK, which has a legal target of net zero by 2050, with huge cuts to emissions and any remaining pollution offset by measures such as planting trees.
The EU has also set a 2050 goal and China has announced ambitions to be carbon neutral by 2060.
And it provides a boost to Britain’s efforts to encourage countries to set out more ambitious climate plans in the run up to a major UN “Cop26” summit in Glasgow next year, as current efforts are not enough to avoid dangerous climate change.
Domestically Mr Biden has pledged 2 trillion dollars over four years as part of efforts to push towards 100 percent clean electricity by 2035, drive take up of zero-emissions vehicles and making buildings more efficient.
Potentially without Democratic control of the Senate, with two races to be decided in run-offs in January, it is not clear how much Mr Biden will be able to achieve at home.
But he has promised a suite of immediate executive actions that do not require agreement from Congress, such as fuel standards, conserving land and curbing methane from oil and gas operations.
He has the support of the majority of Americans, who polling suggests see climate change as a serious problem, want the government to do more to address it, and back policies including developing renewable energy.
He will also be able to make an important contribution on the international stage, where he has pledged that the US will rejoin the Paris Agreement.
Under the global treaty secured in the French capital in 2015, countries have committed to curb temperature rises to “well below” 2C above pre-industrial temperatures and pursue efforts to limit them to 1.5C, which requires cutting emissions to net zero within decades.
The US formally left the accord on Wednesday, the day after the election, the only nation to do so in a move instigated by President Donald Trump who has labelled global warming as a hoax perpetrated by China.
Mr Biden has also signalled a major diplomatic and trade push on climate, promising to rally other countries to more ambitious action and locking in international agreements to reduce emissions in global shipping and aviation.
And he has said he wants to see measures to stop other countries “cheating” on their climate commitments, with a warning of fees or quotas on carbon-intensive goods imported from countries such as China, and moves to stop it subsidising coal exports.
Mr Biden’s approach is the polar opposite to Mr Trump’s talk of houses built with tiny windows and windmills that are extremely expensive and kill all the birds, as he sought to dismiss climate action in the final presidential debate.
While Mr Biden’s climate plans – and what he can achieve – may not go as far as some activists want to see, there is optimism at least that the US is back in the game on tackling global warming.
Lord Stern, who led the seminal review on the economics of climate change for the UK government in 2006, said countries needed to raise their ambition if temperature rises are to be limited to well below 2C.
“The next four years are crucial, and with a US President in office who once again recognises global warming as an existential threat to humanity we have a chance, if we work together, to avoid the worst impacts of climate change.
“There is much work to do but President Biden’s leadership will be of profound importance,” he said.
Laurence Tubiana, chief executive of the European Climate Foundation, said the scales had tipped even further towards a net zero emissions future.
“We welcome the US’s return to the table of global climate leaders, joining the EU, China, Japan, and others with considerable ambition and a promise to work with other countries on their transitions,” she said, adding that the Biden-Harris Administration could enact one of the world’s largest green stimulus packages.
And Climate Action Tracker, an independent scientific analysis of the impact of countries’ pledges on climate change, said Mr Biden’s net zero pledge, if enacted, could shave 0.1C off predicted temperature rises.
Bill Hare, of Climate Analytics, one of the organisations behind the tracker, said that the election could be an historic tipping point, with the US, EU, Japan, South Korea and China – two-thirds of the world economy and 50% of global emissions – all having net zero emissions by mid-century commitments. He said it put the Paris Agreement’s 1.5C target “within striking distance” for the first time ever.
Emily Beament is the PA environment correspondent.