The future of fossil fuels – and whether to agree to phase them “down” or “out” – is shaping up to be a key battle at the COP28 climate talks in Dubai.

While some parties and groups would like to see a deal on phasing out all fossil fuels, others only want to restrict “unabated” coal, oil and gas. Some are opposed to both options.

Meanwhile, alternative formulations are emerging, tying renewable expansion to fossil fuel “substitution”, adding additional verbs such as “accelerating”, adverbs such as “rapidly” or adding timescales such as “this decade”.

The fight over using the phrase “unabated” fossil fuels, implicitly accompanied by its opposite – “abated” – raises the question of exactly what these terms mean.

“Unabated” refers to the burning of fossil fuels where resulting carbon dioxide (CO2) or other greenhouse gas emissions are released directly into the atmosphere, adding to global warming.

Conversely, “abated” refers to the burning of coal, oil and gas combined with the capture and permanent storage of some proportion of the resulting greenhouse gases. This proportion is a key detail as there is no agreed definition of what “abated” means.

In addition to the fight over “unabated”, evidence from the Intergovernmental Panel on Climate Change (IPCC), the International Energy Agency (IEA) and others can be used to inform fossil-fuel discussions at COP28. Key conclusions from their work include:

• The ongoing use of fossil fuels with carbon capture and storage (CCS) features in almost all 1.5C pathways, but only to a very limited extent.
• Today, CCS barely exists and relying on a major scale-up is considered “risky”. If CCS is limited to plausible levels, then fossil fuel use would have to fall even faster.
• While there is disagreement over the difference between “phase down” and “phase out”, the production and use of fossil fuels drops dramatically in all 1.5C pathways.

This Q&A explains the term “unabated fossil fuels”, the science behind fossil-fuel phaseout and the positions of different countries on what should be agreed in relation to fossil fuels at COP28.

• What are ‘abated’ and ‘unabated’ fossil fuels?
• Do fossil fuels have to be phased out to stay below 1.5C?
• What has been agreed on fossil fuel reduction so far?
• Who wants what on fossil fuels at COP28?

What are ‘abated’ and ‘unabated’ fossil fuels?

The Glasgow climate pact, agreed at the COP26 climate talks in 2021, was the first COP decision to mention any fossil fuel – specifically coal – and this reference was tied to the word “unabated”.

However, this word was not defined and there remains a level of uncertainty around what the associated term “abated” actually means in practice. For example, could a coal-fired power plant capture 10% of the CO2 it produces and still argue its emissions were abated?

Disagreement over fossil fuels and “unabated” sprung up again at the COP27 climate talks in 2022 and has continued ever since. (See: What has been agreed on fossil fuel reduction so far?)

Speaking to Carbon Brief, Dr Alaa Al Khourdajie, a research fellow at Imperial College London, says these disagreements highlighted the need to be “transparent and crystal clear about what abated fossil fuels means”. Al Khourdajie says:

“In the absence of such a clear set of criteria, any capture rate – for example, 50-60% – of carbon emissions could be casually considered abated. This cannot be left ambiguous. Looking at the findings of the technical assessment of the first ‘global stocktake’ discussions, the term unabated is used very heavily in the findings.

“But there is a lack of clarity about what counts as unabated and what counts as abated, largely due to the absence of such agreed definitions in the underlying literature at the time of those negotiations.”

The word “unabated” appeared, once again, in the IPCC’s sixth assessment Working Group III report on how to tackle climate change. The report concluded:

“In all scenarios [limiting warming in 2100 to below 1.5C], fossil fuel use is greatly reduced and unabated coal use is completely phased out by 2050.”

(IPCC chair Prof Jim Skea repeated these lines to COP28 delegates, at a 4 December event.)

Moreover, for the first time, the 2022 IPCC report also included a definition of unabated and abated fossil fuels. This definition was added, by Al Khourdajie and other IPCC authors, as a footnote to the summary for policymakers (SPM), after the word “unabated” was added to the summary.

Dr Chris Bataille, adjunct research fellow at the Columbia University Center on Global Energy Policy and one of the other IPCC authors involved in the footnote tells Carbon Brief:

“At the SPM approval session, a group of parties was very insistent on adding the word ‘unabated’ in front of any language on fossil fuels – and that immediately created a need for a definition. A bunch of us [IPCC authors] were concerned to make sure it was defined and so we had to jump in at the last minute to pull something together.”

The IPCC footnote explains that, in order to count as “abated”, at least 90% of fossil-fuel emissions from power plants should be captured and 50-80% of methane from energy supply. It says:

“In this context, ‘unabated fossil fuels’ refers to fossil fuels produced and used without interventions that substantially reduce the amount of GHG emitted throughout the life cycle; for example, capturing 90% or more CO2 from power plants, or 50-80% of fugitive methane emissions from energy supply.”

However, this definition, as drafted, was still somewhat unclear, Bataille tells Carbon Brief. He says the final comma combined with the word “or” implied that this was an alternative to the 90% capture at power plants, whereas the intention had been for both requirements to apply.

In order to clear up this confusion, Al Khourdajie and Bataille published a paper setting out their requirements, in detail, for fossil fuel use to be considered “abated”.

Al Khourdajie tells Carbon Brief:

“We clearly say that the term should be reserved for where the ongoing carbon emissions from using fossil fuels are reduced 90-95% or more; upstream fugitive methane emissions are less than 0.5%, and approaching 0.2%, of equivalent natural gas production; and captured emissions are stored permanently.”

Al Khourdajie notes that the vague definition of “abated” fossil fuel gives a “false, if not dangerous, sense of security” that could lead to inadequate policy measures and investment decisions.

Yet there are some “legitimate uses” of the term, Katrine Petersen, senior policy advisor in thinktank E3G’s fossil fuel transition team, tells Carbon Brief. She says:

“It’s important to note that there are legitimate uses of ‘abatement’ requirements as a route to emissions reductions, too. The use of the term ‘unabated’ in respect to CO2 reduction historically stems from how some governments (such as the UK and Canada) used forms of emissions performance standards to rule out the construction of new coal power plants without CCS, and then to require existing coal power plants to either retrofit CCS to reduce emissions, or instead retire, by certain dates – a regulatory approach that, ultimately, led to no new coal plants being built and clear phase-out dates set, given the high costs and difficulty of CCS. 

“This has been an effective use of abatement standards by policymakers and regulators to force action from the coal power industry. But it required clear definitions and regulation rather than just vague language.”

Even so, there are clear risks to the inclusion of the term “unabated”, says Dr Natalie Jones, policy adviser at thinktank the International Institute for Sustainable Development (IISD).

She tells Carbon Brief that these risks are particularly acute in the setting of the UN climate talks:

“If the word ‘unabated’ is in the final COP28 text, it will be a distraction from the fossil fuel cuts needed this decade to stay below 1.5C. It muddies the water and could mean parties spend the next five years debating definitions.”

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Do fossil fuels have to be phased out to stay below 1.5C?

Fossil fuels are the biggest contributors to current global warming, making up the lion’s share of the cumulative historical emissions that have warmed the Earth by more than 1.2C.

Moreover, existing fossil-fuel infrastructure, if used in line with historical averages, would be sufficient to breach the carbon budget for 1.5C, according to the IPCC. It says:

“Projected cumulative future CO2 emissions over the lifetime of existing and currently planned fossil-fuel infrastructure without additional abatement exceed the total cumulative net CO2 emissions in pathways that limit warming to 1.5C (>50%) with no or limited overshoot.”

Furthermore, continuing to build new fossil-fuel infrastructure would “lock-in” further emissions, the IPCC says with high confidence.

Similarly, the IEA has said there is no space for the development of new, unabated coal-fired power stations or “long-lead time” oil and gas developments, if warming is to stay below 1.5C.

These findings are backed by a “large consensus”, across all published studies, that developing new oil and gas reserves is “incompatible” with staying below 1.5C.

At the aggregate level, the IEA’s 1.5C pathway sees dramatic reductions in unabated fossil fuel use, with only a very small role for abated fossil fuels. This is illustrated in the figure below, which shows that unabated fossil fuel use falls 88% by 2050 and abated fossil fuels remain minimal.

This is just one pathway to staying below 1.5C. The IPCC looks at a wider range of pathways and confirms that reaching net-zero CO2 emissions to stop global warming would entail “substantial” cuts in fossil fuel use, with only “minimal” unabated use remaining and some CCS. It says:

“Net-zero CO2 energy systems entail: a substantial reduction in overall fossil fuel use, minimal use of unabated fossil fuels, and use of CCS in the remaining fossil fuel system.”

The IPCC looked at a range of different ways to keep warming below 1.5C and used “illustrative mitigation pathways” (IMPs) to show how these approaches are similar – and how they differ.

The second row in the figure below shows four IMPs that limit warming in 2100 to 1.5C, from left to right IMP-Neg, IMP-Ren, IMP-LD and IMP-SP. These refer to pathways relying heavily on negative emissions (IMP-Neg), renewable energy (IMP-Ren), low energy demand (IMP-LD) or “shifting development pathways” (IMP-SP).

Note that only the final three IMPs stay below 1.5C with no- or limited “overshoot”, whereas IMP-Neg sees 1.5C temporarily breached.

Fossil fuel use (red) does not reach zero by 2050 in any of these pathways. As such, it is technically correct to say that fossil fuels can still be used in 2050, in pathways respecting 1.5C.

Nevertheless, as with the IEA’s 1.5C pathway, fossil fuel use overall drops very dramatically in all cases. For COP28, the question is how to describe this dramatic reduction in fossil fuel use, which is clearly needed to stay below 1.5C.

There is disagreement over whether a “phase out” refers to a trajectory that reaches zero or whether it simply refers to a very substantial reduction.

Some prefer the term “phase down” for this reason, whereas others feel this implies a weaker reduction than a “phase out”. In addition, “phase down” could mean only a very small cut.

Furthermore, neither of these phrases cover defined periods of time, unless time bounds such as “this decade” or “well before 2050” are explicitly added.

Regardless of the terminology, the amount of fossil fuels still in the system by 2050 is very small, even when including abated fossil fuels as in the figure below. Furthermore, fossil fuel use reaches zero – or close to zero – in the second half of the century in no- or low-overshoot pathways.

Only in the IMP-Neg pathway (leftmost chart in the figure above), where emissions overshoot 1.5C before returning below that level by 2100, is there a larger role for fossil fuels by mid-century.

Here, the ongoing use of fossil fuels is mainly combined with CCS, shown by the grey wedge on the top of the stack in the figure below. (Unabated fossil fuels are shown in dark yellow.)

Notably, in the pathways that stay below 1.5C with no- or minimal overshoot, the use of fossil fuels combined with CCS is almost non-existent. Where CCS is used, it is combined instead with the use of bioenergy (BECCS) or the direct air capture of CO2 from the atmosphere (DACCS).

In addition to noting the minimal role of CCS in 1.5C pathways, it is worth adding that, to date, the technology has failed to scale up to significant levels.

According to the IEA, there are now more than 40 commercial capture facilities in operation globally, with a total annual “capture capacity” of more than 45m tonnes of CO2 (MtCO2).

This capacity can be compared with annual global CO2 emissions that are nearly 1,000 times larger, at an estimated 37bn tonnes of CO2 (GtCO2) in 2023. Put another way, CCS facilities currently capture one tenth of one percent of global CO2 emissions.

The IEA says that momentum behind the technology has been growing since the start of 2018, with more than 50 new capture facilities announced since January 2022.

These could be operating by 2030 and capturing around 125MtCO2 per year. However, only around 20 projects under development have taken a final investment decision, the IEA notes.

Even with this growth in momentum, the pipeline of current projects amounts to only around a third of the level needed under the IEA’s 1.5C pathway in 2030.

For this reason – as well as conflicts with other sustainable development priorities – relying on the significant scaling up of CCS technology would be a “risky” way to respect the 1.5C limit.

(In addition, a new study from the University of Oxford released during COP28, finds that a high-CCS pathway to 1.5C would come with a cumulative $30tn in additional costs by 2050, compared with a low-CCS alternative that relies on faster reductions in fossil fuel use.)

Looking at each of the fossil fuels in turn, in pathways assessed by the IPCC as staying below 1.5C with no- or low-overshoot, there are significant declines in coal use across the board.

In the 1.5C pathway in the middle of the range considered by the IPCC (the median pathway), coal, oil and gas decline by 95%, 60% and 45% by 2050, respectively, compared with 2019 levels.

These median figures hide a wider range for oil and gas. On the other hand, the range gets significantly smaller – and steeper – if pathways are constrained to maximum plausible levels of CCS. In this case, oil and gas see declines of 70% and 84% by 2050, respectively.

Moreover, some countries argue the focus on coal is inequitable, given it tends to be used more heavily in developing countries.

If the pace of coal reductions is eased in these places, then the use of oil and gas – which are more significant in developed countries – would need to fall more steeply.

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What has been agreed on fossil fuel reduction so far?

As already noted, COP26 saw the first COP decision that explicitly called out the need to tackle fossil fuels, with agreement on a “phase down of unabated coal”.

The text in the final agreement at COP26 calls upon parties to: 

“Accelerate the development, deployment and dissemination of technologies, and the adoption of policies, to transition towards low-emission energy systems, including by rapidly scaling up the deployment of clean power generation and energy efficiency measures, including accelerating efforts towards the phasedown of unabated coal power and phase-out of inefficient fossil fuel subsidies, while providing targeted support to the poorest and most vulnerable in line with national circumstances and recognizing the need for support towards a just transition.”

This language was hard-won, with earlier text at the summit having called for efforts to “accelerate the phasing out of coal”. This short wording was ultimately tempered with additional language and, in the final moments of the summit, the phrase “phase out” was changed to “phase down”.

At COP27, parties took up the fight over fossil-fuel language once again, with India calling for agreement to phase down all fossil fuels, with a group of 80 countries calling for a phase out.

Catherine Abreu, executive director of NGO Destination Zero, told Carbon Brief at the time:

“Parties asked for it pretty consistently. More and more parties [joined the call] with every consultation. Their ask for all fossil fuels to be included in the text was ignored every time…The presidency chose not to put those phrases into the drafts.”

Despite countries’ efforts, the Egyptian presidency refused to include fossil-fuel language in any of the draft negotiating texts throughout the two-week summit, leaving many parties disappointed.

Instead, the meeting simply restated the language that had been agreed in Glasgow at COP26 – with even this reiteration having been in doubt at times.

The conversation over cutting fossil fuel use has continued throughout 2023.

In April, the G7 group of major economies held its meeting on climate, energy and environment in Sapporo, Japan. It agreed text using slightly stronger language than that of previous COPs. 

For example, the group emphasised their commitment to “accelerate the phase-out of unabated fossil fuels so as to achieve net-zero in energy systems by 2050 at the latest”. 

The G7 leader’s communiqué reaffirmed a commitment from the previous year’s meeting to achieve a “fully or predominantly decarbonised power sector by 2035”.

This includes taking “concrete and timely steps” towards the goal to “phase-out domestic unabated coal power generation”. It also recognised the need to end the construction of new unabated coal-fired power plants, while working with other nations to support them to do the same.

The G7 agreement added that the member nations ended new direct government support for unabated international thermal coal power generation by the end of 2021, as well as public support for the international unabated fossil fuel energy sector in 2022, except in limited circumstances.

In September, the larger G20 bloc agreed to back global efforts to triple renewable energy capacity by 2030, but failed to find agreed language on fossil fuels.

Following tense negotiations, the group of the world’s largest economies finally secured an agreement at a meeting held in New Delhi, India. The main negotiator Amitabh Kant dubbed the agreement the “most ambitious document on climate action” at a press conference. 

Yet the language with regards to fossil fuels remained in line with what was agreed at COP26 in Glasgow and COP27 in Sharm el-Sheikh.

Reiterating the COP wording, the final G20 agreement called for a transition towards low-emission energy systems, including “accelerating efforts towards phasedown of unabated coal power”. 

Moreover, neither the G7 nor the G20 included a definition of “unabated” and “abated” fossil fuels.

Finally, in mid-November, the US and China – sometimes referred to as the G2 – released their joint “Sunnylands statement” on climate change, which also backed a tripling of renewable energy, but contained only oblique references to cutting the use of fossil fuels.

Rather than talking of phasing fossil fuels down or out, the English-language version says the two countries will ramp up renewables “so as to…substitut[e]” for fossil fuels. It says they:

“[I]ntend to sufficiently accelerate renewable energy deployment in their respective economies through 2030 from 2020 levels so as to accelerate the substitution for coal, oil and gas generation [in the power sector], and thereby anticipate post-peaking meaningful absolute power sector emissions reduction, in this critical decade of the 2020s.”

The statement also commits the pair to at least five “large-scale” CCS cooperation projects for industry and energy, in each country by 2030.

BBC News quoted Bernice Lee, distinguished fellow at Chatham House, as saying that it had likely “proven to be too difficult to find the form of language that works for both” on fossil fuels.

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Who wants what on fossil fuels at COP28?

In the run-up to COP28, key divisions remained on the approach to phasing out or down unabated or abated fossil fuels.

The High Ambition Coalition (HAC) is one of the only blocs to actively support the phasing out of all fossil fuels, both abated and unabated. In a September statement the bloc said:

“Abatement technologies have a role to play in reducing emissions, but that role in the decarbonisation of energy systems is minimal. We cannot use it to green-light fossil fuel expansion.”

It then made a direct call to phase-out fossil fuel production and use within its submission to the global stocktake at the end of October. This submission said:

“Fossil fuels are at the root of this crisis. We must work together to develop a comprehensive global clean energy access approach to accelerate the transition away from fossil fuels.”

With the exception of Colombia, none of the HAC members are fossil-fuel producers of note.

After “fractious” internal negotiations over its position, the EU called for a phase-out of “unabated” fossil fuels – and an energy system “predominantly free of fossil fuels well ahead of 2050”.

Crucially, the bloc’s agreed position also “underlines” limitations on the use of CCS. It says that “emission abatement technologies which do not significantly harm the environment, exist at limited scale and are to be used to reduce emissions mainly from hard to abate sectors”.

Furthermore, it adds that “removal technologies [such as BECCS and DACCS] are to contribute to global negative emissions…[and] should not be used to delay climate action in sectors where feasible, effective and cost-efficient mitigation alternatives are available”.

Speaking in July, then-EU climate chief Frans Timmermans listed the phase-out of unabated fossil fuels as a key goal for the bloc, together with tripling renewables rollout by 2030 and doubling the rate of energy efficiency improvements. 

Timmermans also highlighted the limitation on CCS, saying:

“It is important to have a precise understanding of the role of ‘abated fossils’ in a net-zero economy. These need to be residual and only in hard-to-abate sectors. And the sector carries the burden of proof in demonstrating this is achievable and proposing credible investment strategies in carbon-abating technologies”.

The stances of other key countries and groups can be seen on Carbon Brief’s Who Wants What grid. 

The US is also supporting the phase-out of “unabated” fossil fuels. A statement released by the White House earlier this year argued that the US needs to “accelerate the phase-out of unabated fossil fuels”.

US climate envoy John Kerry backed the use of “abated” fossil fuels, but challenged the oil industry to prove the efficacy of CCS in an interview with the Associated Press earlier this year. He said:

“If you’re able to abate the emissions, capture it. But we don’t have that at-scale yet. And we can’t sit here and just pretend we’re going to automatically have something we don’t have today. Because we might not. It might not work.”

Meanwhile, China’s climate envoy Xie Zhenhua said the phase-out of fossil fuels is “not realistic”, during a speech in Beijing in September.

According to a translation from the Center for China and Globalization, Xie said “completely eliminating fossil energy is not realistic”. 

Going into COP28, sources told Reuters that India would continue to resist those pushing for a deadline on the phasedown of fossil fuels. Instead, it would favour shifting focus to reducing overall carbon emissions through “abatement and mitigation technologies”, the newswire said. 

COP28 host nation the United Arab Emirates (UAE) – a major and expanding fossil fuel producer – has shifted its stance on fossil fuels as 2023 has progressed.

In May, a speech given by COP28 president Sultan Al Jaber said: “We must be laser-focused on phasing out fossil fuel emissions, while phasing up viable, affordable zero-carbon alternatives.”

This was widely interpreted as support for CCS and, with its focus on “fossil fuel emissions”, a deflection from phasing out fossil fuels themselves – a sentiment that drew widespread criticism.

Subsequently, Al Jaber started describing the “phasedown” of fossil fuels as “inevitable” and “essential”, following an interview with the Guardian. 

A pre-summit note issued by the UAE in October calls for a world “working towards an energy system free of unabated fossil fuels by mid-century, with coal being a priority”.

The early draft texts at COP28 shows countries are considering calling for an “orderly and just” phase out of fossil fuels, but whether “unabated” will be included still remains unclear.

As of 5 December, there are three options officially on the table. These are

• “An orderly and just phase out of fossil fuels”;
• “Accelerating efforts towards phasing out unabated fossil fuels and to rapidly reducing their use so as to achieve net-zero CO2 in energy systems by or around mid-century”;
• The third option would be not to mention a fossil fuel phase out (or down) at all.

For many countries, COP28 will not be seen as a success if it fails to agree to language on phasing out all fossil fuels. Whether this is possible – and whether such language will end up being qualified with “unabated” – or some other form of words – remains to be seen.

Strong definitions of abatement could send an important signal at COP28, says Petersen, but could also have real-world implications in driving emissions reductions.

International definitions of abatement could be translated into regulatory standards at national level, she adds, helping countries to reach Paris-aligned emissions reduction levels.

Al Khourdajie says:

“Both [abated and unabated] are certainly used more prominently in international negotiations than ever before. The hope is for the outcomes of the upcoming COP28 to bring clarity to both terms.”

However, he adds that international negotiations should be discussing deeper decarbonisation in developed countries and efforts to support climate action in developing nations, including financial and technological transfer as well as funds for loss and damage. He adds:

“This is the space that discussions in international negotiations should occupy, rather than nuances around abated and unabated fossil fuels, important as they are.”

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Q&A: Why defining the ‘phaseout’ of ‘unabated’ fossil fuels is so important at COP28