Negotiators from around the world began two weeks of talks on curbing climate change today, three years after sealing a landmark deal in Paris that set a goal of keeping global warming well below 2C.
Envoys from almost 200 nations gathered in Poland's southern city of Katowice, a day earlier than originally planned because of the large number of issues that need to be resolved by December 14.
"We are here to enable the world to act together on climate change," said Poland's environmental envoy, Michal Kurtyka, who is presiding over the UN meeting, known as COP24.
With further meetings next year meant to build on what's decided in Katowice, he urged all countries to "show creativity and flexibility".
"The United Nations secretary-general is counting on us, all of us to deliver," Kurtyka said. "There is no Plan B."
Ministers and some heads of government plan to join the discussion tomorrowy, when host Poland is expected to push for a declaration ensuring a "just transition" for fossil fuel industries that face cuts and closures amid efforts to reduce greenhouse gas emissions.
The meeting received a boost over the weekend when 19 major economies at the G20 summit affirmed their commitment to the 2015 Paris climate accord.
The only holdout was the United States, which announced under President Donald Trump that it is withdrawing from the climate pact.
"Despite geopolitical instability, the climate consensus is proving highly resilient," said Christiana Figueres, a former head of the UN climate office.
"It is sad that the federal administration of the United States, a country that is increasingly feeling the full force of climate impacts, continues to refuse to listen to the objective voice of science when it comes to climate change," Figures said.
She cited a recent expert report warning of the consequences of letting average global temperatures rise beyond 1.5C.
"The rest of the G20 have not only understood the science, they are taking actions to both prevent the major impacts and strengthen their economies," said Figueres, who now works with Mission 2020, a group that campaigns to reduce greenhouse gas emissions.
The meeting in Katowice is regarded as a key test of countries' willingness to back their lofty but distant goals with concrete measures, some of which are already drawing fierce protests.
At the top of the agenda is the so-called Paris rulebook, which will determine how governments record and report their greenhouse emissions and efforts to cut them.
Separately, negotiators will discuss ramping up countries' national emissions targets after 2020, and financial support for poor nations that are struggling to adapt to climate change.
The shift away from fossil fuels, which scientists say has to happen by 2050, is expected to require a major overhaul of world economies.
"The good news is that we do know a lot of what we need to be able to do to get there," said David Waskow of the World Resources Institute.
Waskow, who has followed climate talks for years, said despite the Trump Administration's refusal to back this global effort the momentum is going in the right direction.
"It's not one or two players anymore in the international arena. It's what I think you could call a distributed leadership, where you have a number of countries — some of them small or medium-sized — really making headway and doing it in tandem with cities and states and businesses."
Not far from the meeting venue, environmental activists held a small protest to call for an end to coal mining in Poland, which gets some 80 per cent of its energy from coal.
Katowice is in the heart of Poland's coal mining region of Silesia, and there are several active mines in and around the city.
Marches aimed at showing support for ending the use of coal-fired power plants and other efforts to limit climate change drew thousands of people over the weekend in Brussels, Berlin and Cologne.