Nations have begun setting carbon-cutting targets for the decade ahead, and how ambitious these pledges are could make or break global efforts to avoid dangerous levels of climate change.
Nearly 200 countries are supposed to publish updated climate plans by early February, but so far only three have done so.
On Wednesday, the UK became the latest, announcing during the COP29 climate summit in Azerbaijan that it would raise its target to cut greenhouse gas emissions.
All eyes will be on other big polluters like China, India and the United States, though future US climate action is unclear following Donald Trump's election.
The world has agreed to try and limit global warming to 1.5 degrees Celsius above pre-industrial levels, but is nowhere near on track.
Above this threshold, scientists say humanity risks disastrous consequences from volatile weather to major ecological "tipping points" at land and sea.
Last month, the United Nations warned that even if all existing plans are implemented in full, temperatures would rise 2.6C by the century's end, a catastrophic outcome.
The UN says the next round of climate plans must show a "quantum leap" in ambition to avert the worst.
The G20 -- which accounts for 77 percent of total greenhouse gas emissions -- is under particular pressure to step up.
Just before COP29 opened in Azerbaijan, the United Arab Emirates announced a 47 percent reduction in emissions by 2035 compared with 2019 in its updated climate plan.
Observers said the roadmap failed to account for exported emissions -- including those from its sales of crude oil abroad.
Next year's UN climate host, Brazil, has partly unveiled its plan, increasing its emissions reduction target from a 59 percent cut by 2035, from 2005 levels, to a 67 percent reduction.
It is expected to unveil a more complete plan during COP29.
Plans from other major emitters, like the European Union and China, are not expected until next year.
And the current US government could soon outline Washington's new pledge, despite questions over Trump following through once in office.
David Waskow, of the World Resources Institute, said it would help guide American cities, states and businesses wishing to continue climate action under Trump.
"It also sends an important signal internationally, a set of benchmarks for what the US ought to do," he added.
By signing the Paris accord, nearly 200 nations agreed to halt rising temperatures "well below 2C" and strive for the safer goal of 1.5C.
But it did not prescribe how to get there.
The deal left it up to countries to voluntarily chart their own plans and targets, known as Nationally Determined Contributions (NDCs).
These include emission reduction targets and measures to achieve them, such as rolling out renewable energy, electrifying transport, and ending deforestation.
There is no set template for countries to follow but richer countries -- historically the largest emitters -- have a responsibility to pledge the deepest emission cuts.
The plans must be reviewed every five years, with each update supposed to be more ambitious than the last.
This time around countries are expected to improve their 2030 targets and outline economy-wide action they will take to 2035.
An agreement at last year's COP28 climate summit "encouraged" countries to come forward with plans aligned with halting warming to 1.5C.
To have a hope of meeting that goal, emissions must be slashed 42 percent by 2030 and 57 percent by 2035, the UN's Environment Programme said last month.
Currently, however, emissions are continuing to rise.
Keeping 1.5C on track would require a collective effort "only ever seen following a global conflict", it added.
Without pulling together "on a scale and pace never seen before... the 1.5C goal will soon be dead," said UNEP executive director Inger Andersen.
The big moment for assessing progress towards the 1.5C goal comes at a crunch COP30 climate summit in Brazil next year.
Scientists and the International Energy Agency have said that developing new fossil fuel projects is incompatible with halting warming to 1.5C.
But many fossil fuel producing countries argue that new oil and gas projects will be needed as the world transitions to net zero emissions.
Countries are under pressure to outline in their updated plans how they intend to reduce their reliance on fossil fuels, something all nations agreed at last year's COP.
