Countries are being called on to accelerate the phaseout of coal power at the Cop26 summit, and to return to the negotiating table next year with improvements to their national plans on cutting greenhouse gases.

The second draft of the key outcome from the Cop26 summit, now nearing its final hours in Glasgow after a fortnight of intense talks, showed a slight softening of language in some instances but retained the core demands for a return.

The three architects of the landmark 2015 Paris climate agreement have told the Guardian that a return to the negotiating table next year to revise countries’ national emissions-cutting targets – known as nationally determined contributions (NDCs) – must be the key outcome of the talks if the world is to limit global heating to 1.5C.

There was a slight change in the language in the text with regards to NDC revisions – the previous text, published on Thursday morning, “urged” parties to make revisions, while the current draft “requests” them to do so. However, the latter mirrors the language used in the Paris agreement, so the change was not regarded as a significant weakening.

The latest draft proposal from the Cop26 chair, released soon after 7am on Friday in Glasgow, calls on countries to accelerate “the phaseout of unabated coal power and of inefficient subsidies for fossil fuels.”

A previous version on Wednesday had called on countries to “accelerate the phasing out of coal and subsidies for fossil fuel.”

The addition of “inefficient” could help countries that want to retain some fuel subsidies for the poor, while removing subsidies for major fossil fuel interests. This change to the language could also provide cover for countries that want to retain subsidies, however.

The issue of fossil fuel subsidies has long vexed climate experts, with calls to reduce the subsidies over two decades going largely unheeded. However, to have any language on phasing out fossil fuels and subsidies to them in the cover decision of a Cop is new and if the provision is retained in the final outcome it will mark an increased determination by many countries to face down fossil fuel producers at the talks.

A requirement for countries to revise NDCs reflects the expression of alarm by many parties, including the most vulnerable developing countries, over the chasm between carbon targets and the deep cuts necessary to limit temperature rises to 1.5C above pre-industrial levels.

Current national plans – known as nationally determined contributions (NDCs) – would lead to 2.4C of heating, according to an influential analysis this week by Climate Action Tracker.

Countries are currently expected to return with better pledges in 2025, under the Paris agreement, but many are now demanding the deadline should be brought forward. This is seen as the most closely fought area of disagreement as the UK hosts struggle to broker a deal.

The question of when and how to revise NDCs is crucial because although the Glasgow talks will continue at least to the end of Friday, and probably well into this weekend, there is now no possibility that governments will toughen their NDCs at this summit. But a clause in the draft text that will form the main outcome of the talks would allow for a return next year to update and strengthen the targets.

Developing countries are concerned that there is not enough reassurance for them for them on climate finance, a core issue for countries struggling to cope with the impacts of extreme weather.

Helen Mountford of the World Resources Institute said that the draft showed some progress in this area. “Some elements look like they could be stronger, particularly adaptation, finance and loss and damage, that was really very much needed,” she said. These issues are the funding for clean development, adapting to climate impacts and paying for unavoidable damage. “It is now giving specific dates, requesting countries to double adaptation finance by the end of 2025.”

But she added: “On the $100 billion [promised] from 2020 annually, there’s still no reference to making up the shortfall since we know countries failed to meet that goal in 2020 and 2021. So that’s definitely a gap.” The $100bn was promised back in 2009, to be delivered in 2020 and the failure has damaged trust between rich donor nations and poorer recipient nations.

Experts said on Friday morning that negotiators would now be in close consultation with senior officials in their country capitals, as aspects of the text would need to be decided at the highest levels of government for many countries. The text is regarded as strong by many developing countries, but they expect it to come under fierce attack today from fossil fuel producing countries in particular.

Finance ministers are expected to meet at 11am, with a stock take by all parties expected at midday. The UK’s Cop president Alok Sharma is engaged in last-minute shuttle diplomacy among parties.

Bob Ward, of the Grantham Research Institute on Climate Change said: “This text appears to deal with many of the major issues that need to be resolved, but some important aspects still need to be finalised and may take some time to conclude. The text “requests”, rather than commits, countries to deliver updated and more ambitious pledges by the end of next year, recognising that the planned emissions cuts collectively are still not consistent with holding warming to no more than 1.5 Celsius degrees.”

But he added: “The call for countries to phase-out unabated coal power and inefficient fossil fuel subsidies is very important and historic. Unabated coal power releases carbon dioxide into the atmosphere, and all subsidies for fossil fuels are inefficient.”

Since the Paris agreement was signed, binding countries to limit temperature rises “well below” 2C above pre-industrial levels while “pursuing efforts” to a 1.5C limit, new science has shown that breaching the 1.5C threshold would lead to disastrous impacts, some irreversible, including the inundation of many low-lying areas. Heating has now reached 1.1C, and extreme weather is already taking hold around the world.

The Intergovernmental Panel on Climate Change has said emissions must be cut by 45% by 2030 compared with 2030 levels to stay within 1.5C.

The new draft outcome text will be discussed ahead of the 6pm UK time deadline for the talks to finish. However, previous Cop summits have a history of going well into Saturday and sometimes Sunday.

More updates soon …