Documents leaked ahead of the United Nations' COP26 climate talks show how some fossil fuel-producing nations have been pressuring the Intergovernmental Panel on Climate Change (IPCC) to amend a draft report that threatens their domestic economic interests.

The documents – leaked to Greenpeace UK's team of investigative journalists, Unearthed – show how fossil fuel producers including Australia, Saudi Arabia and other Opec members are lobbying the IPCC to remove or weaken a key conclusion that the world needs to rapidly phase out fossil fuels.

Several nations are attempting to water down IPCC’s draft report that outlines the world’s options for limiting global warming. The disclosure comes just days before the start of crucial international climate negotiations (COP26).

The leak reveals tens of thousands of comments by governments, companies, academics and other stakeholders to the IPCC’s ‘Working Group III’ — an international team of experts that is drafting the panel's latest report assessing humanity’s remaining options for curbing greenhouse gas emissions or removing them from the atmosphere.

These IPCC reports are used by governments to determine what action is needed to tackle climate change, and the latest will be a crucial input to negotiations at COP26 in Glasgow, which starts on 31 October.

The authority of these reports derives in part from the fact that virtually all the governments of the world participate in the process to reach consensus.

The leaked documents show a number of countries and organisations arguing that the world does not need to reduce the use of fossil fuels as quickly as the current draft of the report recommends.

An advisor to the Saudi oil ministry reportedly demands "phrases like 'the need for urgent and accelerated mitigation actions at all scales...' should be eliminated from the report".

Meanwhile, the BBC reported a senior Australian government official rejecting the report's conclusion that shutting down coal-fired power plants is necessary, even though ending the use of coal is one of the stated objectives of COP26.

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Climate scientist Simon Lewis, professor of global change science at University College London, told Unearthed: “These comments show the tactics some countries are willing to adopt to obstruct and delay action to cut emissions.

“On the eve of the crucial COP26 talks there is, to me, a clear public interest in knowing what these governments are saying behind the scenes.”

Lewis added: “Like most scientists I’m uncomfortable with leaks of draft reports, as in an ideal world the scientists writing these reports should be able to do their job in peace. But we don’t live in an ideal world, and with emissions still increasing, the stakes couldn’t be higher.”

Saudi Arabia, China, Australia and Opec all support carbon capture and storage (CCS), which has been highlighted as a way to dramatically reduce emissions from power plants and some industrial sectors.

However, Saudi Arabia requested that UN scientists remove their conclusion that "the focus of decarbonisation efforts in the energy systems sector needs to be on rapidly shifting to zero-carbon sources and actively phasing out fossil fuels".

Argentina, Norway and Opec also took issue with that conclusion, according to the BBC, which reported Norway as arguing that UN scientists should allow the possibility of CCS as a potential tool for reducing emissions from fossil fuels.

The IPCC’s draft report accepts CCS could play a role in the future but claims there are uncertainties about its feasibility.

It states "there is large ambiguity in the extent to which fossil fuels with CCS would be compatible with the 2 degrees Celsius and 1.5 Celsius targets" as set out by the Paris Agreement.

Opec told the BBC: "The challenge of tackling emissions has many paths, as evidenced by the IPCC report, and we need to explore them all. We need to utilise all available energies, as well as clean and more efficient technological solutions to help reduce emissions, ensuring no one is left behind."

The IPCC said comments from governments are central to its scientific review process and that its authors have no obligation to incorporate them into the reports.

"Our processes are designed to guard against lobbying — from all quarters", the IPCC told the BBC.

"The review process is (and always has been) absolutely fundamental to the IPCC's work and is a major source of the strength and credibility of our reports.”

Meanwhile, Brazil and Argentina, two of the largest producers of beef products and animal feed crops in the world, argued against evidence in the draft report that reducing meat consumption is necessary to cut greenhouse gas emissions.

The draft report states "plant-based diets can reduce greenhouse gas emissions by up to 50% compared to the average emission intensive Western diet".

Argentina and Brazil urged the IPCC authors to delete or change some passages in the text referring to "plant-based diets" playing a role in tackling climate change, or which describe beef as a "high carbon" food.

The BBC further reported that a significant number of Switzerland's comments were directed at amending parts of the IPCC draft report that argue developing countries will need support, particularly financial support, from rich countries in order to meet emission reduction targets.

It was agreed at the climate conference in Copenhagen in 2009 that developed nations would provide $100 billion annually in climate finance for developing countries by 2020, a target that has yet to be met.