An agreement struck between the US and China is a welcome boost as negotiators make their final efforts to secure a long-term deal to limit global warming to 1.5C at the UN's Cop26 climate change summit in Scotland, the UK's Prime Minister Boris Johnson said on Thursday.
The world's two largest emitters of carbon dioxide unveiled a deal on Wednesday to increase their cooperation on tackling climate change, including cutting methane emissions, phasing out coal consumption and protecting forests.
The surprise announcement came despite tensions between the two superpowers and signalled that the countries' leaders were prepared to put aside their difference to work together on the common threat to the planet, said analysts.
Mr Johnson said on Twitter that that deal was a sign that countries could keep alive the prospect of limiting global warming to 1.5C above pre-industrial levels.
"This is a boost to negotiations as we go into the final days of Cop26 and continue working to deliver an ambitious outcome for the planet," he said.
Alok Sharma, head of the UN climate conference, has warned that climate commitments so far in the talks would do too little to tame global warming and demanded an ambitious deal to be struck over the next few days.
"I want to be clear, we are not there yet, there's still a lot more work to be done," he said. "I know how hard you are all working, but today must represent another gearshift where negotiators finalise outstanding technical work and ministers dial up their engagement," he said.
The framework agreement was announced by US climate envoy John Kerry and his Chinese counterpart Xie Zhenhua at the summit in Scotland, billed by both as way to tip the summit towards success.
“Together we set out our support for a successful Cop26, including certain elements which will promote ambition,” Mr Kerry told a news conference about the deal between Washington and Beijing.
“Every step matters right now and we have a long journey ahead of us.”
Mr Xie told reporters that the deal would lead to China strengthening its emissions-cutting targets.
“Both sides will work jointly and with other parties to ensure a successful Cop26 and to facilitate an outcome that is both ambitious and balanced,” Mr Xie said.
A first draft of the Cop26 deal released earlier in the day received a mixed response from climate activists and experts.
Representatives from almost 200 countries in Glasgow have until the close of the two-week meeting on Friday to agree on a final text.
In an implicit acknowledgement that current pledges were insufficient to avert climate catastrophe, the draft asks countries to “revisit and strengthen” by the end of next year their targets to reduce greenhouse gas emissions up to 2030.
EU climate policy chief Frans Timmermans told Reuters the US-China agreement inspired hope.
“It's really encouraging to see that those countries that were at odds in so many areas have found common ground on what is the biggest challenge humanity faces today,” he said.
“It shows also that the US and China know this subject transcends other issues. And it certainly helps us here at Cop to come to an agreement.”
But E3G, a European climate change think tank, said that the deal did not include any new commitments on the crucial issue of coal.
China has pledged to peak coal consumption before 2030 and go carbon neutral by 2060 but has yet to spell out how it will achieve the goals. Environmentalists have warned that China could keep increasing emissions until 2030 under its current commitments.
"This declaration is a reassuring sign that the world’s two biggest emitters can work together on the biggest crisis humanity is facing," said senior E3G policy advisor Byford Tsang.
"But to walk the talk they’d now need to support a strong political commitment at the COP26 on mitigation and climate finance, and rally other countries to do the same."
The statement from the two global powers was not enough to "close the deal", said Bernice Lee, research director at the Chatham House think tank. "The real test of Washington and Beijing is how hard they push for a 1.5C aligned deal here in Glasgow."
Scientific evidence has grown suggesting that crossing the 1.5C threshold will significantly worsen extreme weather effects, including droughts, flooding and wildfires, and could wipe out some species.
Mr Johnson has made a goal of the conference to "keep 1.5 alive" but environmental groups said that pledges so far did not amount to a significant change. The Climate Action Tracker research group earlier this week said all national pledges submitted so far to cut greenhouse gases by 2030 would, if fulfilled, allow the Earth's temperature to rise 2.4C.
Negotiations are still likely to be fierce over the next two days.
While some developed countries point the finger at major polluters such as China, India and Russia, poorer nations accuse the rich world of failing to keep promises of financial help to deal with the ravages of climate change.
As delegations locked horns over the wording of the final statement, a group of countries, companies and cities composed a pledge committed to phasing out fossil fuel-powered vehicles by 2040.
The overarching goal of the conference is to keep alive hopes of capping global temperatures at 1.5°C above pre-industrial levels, which is unachievable based on most countries' current emissions-cutting pledges.
That aspirational target was set out in the 2015 Paris Agreement. Since then, scientific evidence has shown that crossing the 1.5°C threshold will unleash worse rises in sea levels, floods, droughts, fires and storms than those already occurring, with irreversible consequences.