More than 200 scientists told the COP26 summit Thursday to take immediate action to halt global warming, warning in an open letter that some climate change impacts were "irreversible" for generations.

The central task of the Glasgow meeting is to implement the Paris Agreement, with its goal of limiting temperature rise to between 1.5 and 2 degrees Celsius above pre-industrial levels.

But as negotiations enter their final days, commitments made so far could still lead to "catastrophic" warming of as much as 2.7C by 2100, according to the UN.

"We, climate scientists, stress that immediate, strong, rapid, sustained and large-scale actions are necessary," to keep warming within the Paris target, said the letter, signed by researchers across the world.

In August, a bombshell "code red" report from the world's top climate science body, the Intergovernmental Panel on Climate Change (IPCC), warned that Earth's average temperature will hit the 1.5C threshold around 2030, a decade earlier than projected only three years ago.

To keep from overshooting that temperature target the IPCC says emissions must fall 45 percent this decade.

Thursday's open letter, signed by some of the IPCC's report authors, calls on delegates in Glasgow to "fully acknowledge" the scientific evidence they have compiled of the severe threats posed by climate change.

"COP26 is a historic moment for the fate of climate, societies and ecosystems, because human activities have already warmed the planet by around 1.1C and future greenhouse gas emissions will determine future additional warming," the letters said.

The heating atmosphere is already magnifying weather extremes, subjecting communities across the world to more intense fire and drought, displacement and severe economic hardship.

And emissions are still rising.

A major recent assessment showed global CO2 emissions are set to rebound in 2021 to pre-pandemic levels.

"Cumulative greenhouse gas emissions to date already commit our planet to key changes of the climate system affecting human society and marine and terrestrial ecosystems, some of which are irreversible for generations to come," said the letter.

COP26 climate summit gears up for fraught final hours
Glasgow (AFP) Nov 12, 2021 –

UN climate talks headed towards a rocky conclusion Friday after two weeks of fraught debate failed to resolve several key disputes or produce the emissions cutting plans needed to limit global warming to 1.5C.

"The world is watching us", COP26 President Alok Sharma told delegates charged with keeping the Paris Agreement temperature goals alive even as climate-driven disasters hit countries the world over.

The summit began with a bang as world leaders descended on Glasgow armed with a string of headline announcements, from a commitment to slash methane emissions to a plan to save the rainforests.

But progress has stalled in the underlying technical and now minister-level negotiations.

With one day left of scheduled talks, countries are hardly any closer to agreement over whether national emissions cutting plans must be ramped up in the short term, how climate action is reported, and how vulnerable nations are supported.

"The truth is that the atmosphere doesn't care about commitments," said Ugandan youth activist Vanessa Nakate.

"It only cares about what we put into it or stop putting into it. Humanity will not be saved by promises."

Draft decision texts urged countries to speed up their decarbonisation plans and submit renewed contributions by 2022, three years sooner than planned.

They also included a rare mention of fossil fuels — anathema to large hydrocarbon producers but a key ask of the European Union and other advanced economies.

Host Britain says it wants COP26 to lead to commitments from countries to keep the 1.5C temperature cap goal of the Paris agreement within reach.

However, current national emissions cutting plans, all told, would lead to 2.7C of heating.

UN Secretary Antonio Guterres said Thursday that countries' climate plans were "hollow" without commitments to rapidly phase out fossil fuels.

– US-China pact –

Negotiations received a shot in the arm Wednesday when the United States and China — the two largest emitters — unveiled a joint climate action plan.

Although it was light on detail, observers said the pact allayed concerns that frosty US-China relations entering into COP26 would derail the talks.

But trust levels between rich polluters and developing nations are low after developed countries failed to stump up the $100 billion a year they promised by 2020.

Finance more generally is holding up progress in Glasgow, with developing nations insisting on more money for adaptation that can help them brace for future climate shocks.

Developed nations meanwhile favour a greater push on emissions reductions, something countries yet to fully electrify their grids — and largely blameless for emissions — feel is unfair.

"We have made steps forward," European Commission vice president Frans Timmermans told AFP.

"It's not enough to address the issue that we face, but we're having a completely different conversation now than we had only a couple of months ago. Adaptation has really gone up on our global agenda."

Countries already battered by climate disasters such as record-breaking drought and flooding are demanding they be compensated separately for "loss and damage".

Organisers said the draft texts dedicated an "unprecedented" section to loss and damage, but vulnerable nations said it stopped far short of their expectations.

Other issues likely to delay an agreement in Glasgow include a long-simmering dispute over the rules governing carbon markets, and common reporting timeframes.