The first-ever international conference on the contentious topic of “overshoot” was held last week in a palace in the small town of Laxenburg in Austria.
The three-day conference brought together nearly 200 researchers and legal experts to discuss future temperature pathways where the Paris Agreement’s “aspirational” target to limit global warming to 1.5C is met “from above, rather than below”.
Overshoot pathways are those which exceed the 1.5C limit – before being brought back down again through techniques that remove carbon from the atmosphere.
The conference explored both the feasibility of overshoot pathways and the legal frameworks that could help deliver them.
Researchers also discussed the potential consequences of a potential rise – and then fall – of global temperatures on climate action, society and the Earth’s climate systems.
Speaking during a plenary session, Prof Joeri Rogelj, a professor of climate science and policy at Imperial College London, said that “moving into a world where we exceed 1.5C and have to manage overshoot” was an exercise in “managing failure”.
He said that it was “essential” that this failure was acknowledged, explaining that this would help set out the need to “minimise and manage” the situation and clarify the implications for “near-term action” and “long-term [temperature] reversal”.
Below, Carbon Brief draws together some of the key talking points, new research and discussions that emerged from the event.
- Defining overshoot
- Mitigation ambition and 1.5C viability
- Carbon removal
- Impacts of overshoot
- Adaptation
- Legal implications and loss and damage
- Communication challenges and next steps
Defining overshoot
The study of temperature overshoot has grown in recent years as the prospects of limiting global temperature rise to 1.5C have dwindled.
Conference organiser Dr Carl-Friedrich Schleussner – a senior research scholar at the International Institute for Applied Systems Analysis (IIASA) – explained the event was designed to bring together different research communities working on a “new field of science”.
He told Carbon Brief:
“If we look at [overshoot] in isolation, we may miss important parts of the bigger picture. That’s why we also set out the conference with very broad themes and a very interdisciplinary approach.”
The conference was split between eight conference streams: mitigation ambition; carbon dioxide removal (CDR); Earth system responses; climate impacts; tipping points; adaptation; loss and damage; and legal implications.
There was also a focus on how to communicate the concept of overshoot.
In simple English, “overshoot” means to go past or beyond a limit. But, in climate science, the term implies both a failure to meet a target – as well as subsequent action to correct that failure.
Today, the term is most often deployed to describe future temperature trajectories that exceed the Paris Agreement’s 1.5C limit – and then come back down.
(In the Intergovernmental Panel on Climate Change’s (IPCC’s) fifth assessment cycle, completed in 2014, the term was used to describe a potential rise and then fall of CO2 concentrations above levels recommended to meet long-term climate goals. A recent “conceptual” review of overshoot noted this was because, at the time, CO2 concentrations were the key metric used to contextualise emissions reductions).
The plot below provides an illustration of three overshoot pathways. The most pronounced pathway sees global temperatures rise significantly above the 1.5C limit – before eventually falling back down again as carbon dioxide is pulled from the atmosphere at scale.
In the second and third pathways, global temperature rise breaches the limit by a smaller margin, before either falling enough just to stabilise around 1.5C, or dropping more dramatically due to larger-scale carbon removals.
In an opening address to delegates, Prof Jim Skea, who is the current chair of the IPCC, acknowledged the scientific interpretation of overshoot was not intuitive to non-experts.
“The IPCC has mainly used two words in relation to overshoot – “exceeding” and “limiting”. To a lay person, these can sound like opposites. Yet we know that a single emissions pathway can both exceed 1.5C in the near term and limit warming to 1.5C in the long term.”
Noting that different research communities were using the term differently, Skea urged researchers to be precise with terminology and stick to the IPCC’s definition of overshoot:
“We should give some thought to communication and keep this as simple as possible. When I look at texts, I hear more poetic words like “surpassing” and “breaching”. I would urge you to keep the range of terms as small as possible and make sure that we’re absolutely using them consistently.”
In the glossary for its latest assessment cycle, AR6, the IPCC defines “overshoot” pathways as follows:
IIASA’s Schleussner stressed that not all pathways that go beyond 1.5C qualify as overshoot pathways:
“The most important understanding is that overshoot is not any pathway that exceeds 1.5C. An overshoot pathway is specific to this being a period of exceedance. It is going to come back down below 1.5C.”
Mitigation ambition and 1.5C viability
Perhaps the most prominent topic during the conference was the implications of overshoot for global ambition to cut carbon emissions and the viability of the 1.5C limit.
Opening the conference, IIASA director general Prof Hans Joachim Schellnhuber shared his personal view that “1.5C is dead, 2C is in agony and 3C is looming”.
In a pre-recorded keynote speech, Ralph Regenvanu, Vanuatu’s minister for climate change, called for a rejection of the “normalisation of overshoot” and argued that “we must treat 1.5C as the absolute limit that it is” and avoid backsliding. He added:
“Minimising peak warming must be our lodestar, because every tenth of a degree matters.”
Prof Skea opened his keynote with some theology:
“I’m going to start with the prayer of St Augustine as he struggled with his youthful longings: ‘Lord grant me chastity and continence, but not yet.’ And it does seem that this is the way that the world as a whole is thinking about 1.5C: ‘Lord, limit warming to 1.5C above pre-industrial levels, but not yet.’”
Referencing the “lodestar” mentioned by Regenvanu, Skea warned that it is light years away and, “unless we act with a sense of urgency, [1.5C is] likely to remain just as remote”.
Speaking to Carbon Brief on the sidelines of the conference, Skea added:
“We are almost certain to exceed 1.5C and the viability of 1.5C is now much more referring to the long-term potential to limit it through overshoot.”
Schleussner told Carbon Brief that the framing of 1.5C in the conference is “one that further solidifies 1.5C as the long-term limit and, therefore, provides a backstop against the idea of reducing or backsliding on targets”.
If warming is going to surpass 1.5C, the next question is when temperatures are going to be brought back down again, Schleussner added, noting that there has been no “direct” guidance on this from climate policy:
“The [Paris Agreement’s] obligation to “pursue efforts” [to limit global temperature rise by 1.5C] points to doing it as fast as possible. Scientifically, we can determine what this means – and that would be this century. But there’s no clear language that gives you a specific date. It needs to be a period of overshoot – that is clear – and it should be as short as possible.”
In a parallel session on the “highest possible mitigation ambition under overshoot”, Prof Joeri Rogelj, professor of climate science and policy at Imperial College London, outlined how the recent ruling from the International Court of Justice (ICJ) provides guidance to countries on the level of ambition in their climate pledges under the Paris Agreement, known as “nationally determined contributions” (NDCs). He explained:
“[The ruling] highlights that the level of NDC ambition is not purely discretionary to a state and that every state must do its utmost to ensure its NDC reflects the highest possible ambition to meet the Paris Agreement long-term temperature goal.”
Rogelj presented some research – due to be published in the journal Environmental Research Letters – on translating the ICJ’s guidance “into a framework that can help us to assess whether an NDC indeed is following a standard of conduct that can represent the highest level of ambition”. He showed some initial results on how the first two rounds of NDCs measure up against three “pillars” covering domestic, international and implementation considerations.
In the same session, Prof Oliver Geden, senior fellow and head of the climate policy and politics research cluster at the German Institute for International and Security Affairs and vice-chair of IPCC Working Group III, warned that the concept of returning temperatures back down to 1.5C after an overshoot is “not a political project yet”.
He explained that there is “no shared understanding that, actually, the world is aiming for net-negative”, where emissions cuts and CDR together mean that more carbon is being taken out of the atmosphere than is being added. This is necessary to achieve a decline in global temperatures after surpassing 1.5C.
This lack of understanding includes developed countries, which “you would probably expect to be the frontrunners”, Geden said, noting that Denmark is the “only developed country that has a quantified net-negative target” of emission reductions of 110% in 2050, compared to 1990 levels. (Finland also has a net-negative target, while Germany announced its intention to set one last year. In addition, a few small global-south countries, such as Panama, Suriname and Bhutan, have already achieved net-negative.)
Geden pondered whether developed countries are a “little bit wary to commit to going to net-negative territory because they fear that once they say -110%, some countries will immediately demand -130% or -150%” to pay back a larger carbon debt.
Carbon removal
To achieve a decline in global temperatures after an initial breach of 1.5C would require the world to reach net-negative emissions overall.
There is a wide range of potential techniques for removing CO2 from the atmosphere, such as afforestation, direct air capture and bioenergy with carbon capture and storage (BECCS). Captured carbon must be locked away indefinitely in order to be effective at reducing global temperatures.
However, despite its importance in achieving net-negative emissions, there are “huge knowledge gaps around overshoot and carbon dioxide removal”, Prof Skea told Carbon Brief. He continued:
“As it’s very clear from the themes of this conference, we don’t altogether understand how the Earth would react in taking carbon dioxide out of the atmosphere. We don’t understand the nature of the irreversibilities. And we don’t understand the effectiveness of CDR techniques, which might themselves be influenced by the level of global warming, plus all the equity and sustainability issues surrounding using CDR techniques.”
Skea notes that the seventh assessment cycle of the IPCC, which is just getting underway, will “start to fill these knowledge gaps without prejudging what the appropriate policy response should be”.
Prof Nebojsa Nakicenovic, an IIASA distinguished emeritus research scholar, told Carbon Brief that his “major concern” was whether there would be an “asymmetry” in how the climate would respond to large-scale carbon removal, compared to its response to carbon emissions.
In other words, he explained, would global temperatures respond to carbon removal “on the way down” in the same way they did “on the way up” to the world’s carbon emissions.
Nakicenovic noted that overshoot requires a change in focus to approaching the 1.5C limit “from above, rather than below”.
Schleussner made a similar point to Carbon Brief:
“We may fail to pursue [1.5C] from below, but it doesn’t relieve us from the obligation to then pursue it from above. I think that’s also a key message and a very strong overarching message that’s going to come out from the conference that we see…that pursuing an overshoot and then decline trajectory is both an obligation, but it also is well rooted in science.”
Reporting back to the plenary from one of the parallel sessions on CDR, Dr Matthew Gidden, deputy director of the Joint Global Change Research Institute at the Pacific Northwest National Laboratory, also noted another element of changing focus:
“When we’re talking about overshoot, we have become used to, in many cases, talking about what a net-zero world looks like. And that’s not a world of overshoot. That’s a world of not returning from a peak. And so communicating instead about a net-negative world is something that we could likely be shifting to in terms of how we’re communicating our science and the impacts that are coming out of it.”
On the need for both CDR and emissions cuts, Gidden noted that the discussions in his session emphasised that “CDR should not be at the cost of mitigation ambition”. But, he added, there is still the question of how “we talk about emission reductions needed today, but also likely dependence on CDR in the future”.
In a different parallel session, Prof Geden also made a similar point, noting that “we have to shift CDR from being seen as a barrier to ambition to an enabler of even higher ambition, but not doing that by betting on ever more CDR”.
Among the research presented in the parallel sessions on CDR was a recent study by Dr Jay Fuhrman from the JGCRI on the regional differences in capacity to deploy large-scale carbon removal. Ruben Prütz, from the Potsdam Institute for Climate Impact Research, presented on the risks to biodiversity from large-scale land-based CDR, which – in some cases – could have a larger impact than warming itself.
In another talk, the University of Oxford’s Dr Rupert Stuart-Smith explored how individual countries are “depending very heavily on [carbon] removals to meet their climate targets”. Stuart-Smith was a co-author on an “initial commentary” on the legal limits of CDR, published in 2023. This has been followed up with a “much more detailed legal analysis”, which should be published “very soon”, he added.
Impacts of overshoot
Since the Paris Agreement and the call for the IPCC to produce a special report on 1.5C, research into the impacts of warming at the aspirational target has become commonplace.
Similarly, there is an abundance of research into the potential impacts at other thresholds, such as 2C, 3C and beyond.
However, there is comparatively little research into how impacts are affected by overshoot.
The conference included talks on some published research into overshoot, such as the chances of irreversible glacier loss and lasting impacts to water resources. There were also talks on work that is yet to be formally published, such as the risks of triggering interacting tipping points under overshoot.
Speaking in a morning plenary, Prof Debra Roberts, a coordinating lead author on the IPCC’s forthcoming special report on climate change and cities and a former co-chair of Working Group II, highlighted the need to consider the implications of different durations and peak temperatures of overshoot.
For example, she explained, it is “important to know” whether the impacts of “overshoot for 10 years at 0.2C above 1.5C are the same as 20 years at 0.1C of overshoot”.
Discussions during the conference noted that the answer may be different depending on the type of impact. For heat extremes, the peak temperature may be the key factor, while the length of overshoot will be more relevant for cumulative impacts that build up over time, such as sea level rise.
Similarly, if warming is brought back down to 1.5C after overshoot, what happens next is also significant – whether global temperature is stabilised or net-negative emissions continue and warming declines further. Prof Schleussner told Carbon Brief:
“For example, with coastal adaptation to sea level rise, the question of how fast and how far we bring temperatures back down again will be decisive in terms of the long-term outlook. Knowing that if you stabilise that around 1.5C, we might commit two metres of sea level rise, right? So, the question of how far we can and want to go back down again is decisive for a long-term perspective.”
One of the eight themes of the conference centred specifically on the reversibility or irreversibility of climate impacts.
In his opening speech, Vanuatu’s Ralph Regenvanu warned that “overshooting 1.5C isn’t a temporary mistake, it is a catalyst for inescapable, irreversible harm”. He continued:
“No level of finance can pull back the sea in our lifetimes or our children’s. There is no rewind button on a melted glacier. There is no time machine for an extinct species. Once we cross these tipping points, no amount of later ‘cooling’ can restore our sacred reefs, it cannot regrow the ice that already vanished and it cannot bring back the species or the cultures erased by the rising tides.”
As an example of a “deeply, deeply irreversible” impact, Dr Samuel Lüthi, a postdoctoral research fellow in the Institute of Social and Preventive Medicine at the University of Bern, presented on how overshoot could affect heat-related mortality.
Using mortality data from 850 locations across the world, Lüthi showed how projections under a pathway where warming overshoots 1.5C by 0.1-0.3C, before returning to 1.5C by 2100 has 15% more heat-related deaths in the 21st century than a pathway with less than 0.1C of overshoot.
His findings also suggested that “10 years of 1.6C is very similar [in terms of impacts] to five years of 1.7C”.
Extreme heat also featured in a talk by Dr Yi-Ling Hwong, a research scholar at IIASA, on the implications of using solar geoengineering to reduce peak temperatures during overshoot.
She showed that a world where a return to 1.5C had been achieved through geoengineering would see different impacts from a world where 1.5C was reached through cutting emissions. For example, in her modelling study, while geoengineering restores rainfall levels for some regions in the global north, significant drying “is observed in many regions in the global south”.
Similarly, a world geoengineered to 1.5C would see extreme nighttime heat in some tropical regions that is more severe than in a 2C world with no geoengineering, Hwong added.
In short, she said, “this implies the risk of creating winners and losers” under solar geoengineering and “raises concerns about equity and accountability that need to be considered”.
After describing how overshoot features in the outlines of the forthcoming AR7 reports in his opening speech, Prof Skea told Carbon Brief that he expects a “surge of papers” on overshoot in time to be included.
But it was important to emphasise that a “lot of the science that people have been carrying out is relevant within or without an overshoot”, he added:
“At points in the future, we are not going to know whether we’re in an overshoot world or just a high-emissions world, for example. So a lot of the climate research that’s been done is relevant regardless of overshoot. But overshoot is a new kind of dimension because of this issue of focus on 1.5C and concerns about its viability.”
Adaptation
The implications of overshoot temperature pathways for efforts to prepare cities, countries and citizens for the impacts of climate change remains an under-researched field.
Speaking in a plenary, Prof Kristie Ebi – a professor at the University of Washington’s Center for Health and the Global Environment – described research into adaptation and overshoot as “nascent”. However, she stressed that preparing society for the impacts associated with overshoot pathways was as important as bringing down emissions.
She told Carbon Brief that there were “all kinds of questions” about how to approach “effective” adaptation under an overshoot pathway, explaining:
“At the moment, adaptation is primarily assuming a continual increase in global mean surface temperature. If there is going to be a peak – and, of course, we don’t know what that peak is – then how do you start planning? Do you change your planning? There are places, for instance when thinking about hard infrastructure, [where overshoot] may result in a change in your plan.”
IIASA’s Schleussner told Carbon Brief that the scientific community was only just “beginning to appreciate” the need to understand and “quantify” the implications of different overshoot pathways on adaptation.
In a parallel session, Dr Elisabeth Gilmore, associate professor in environmental engineering and public policy at Carleton University in Canada, made the case for overshoot modelling pathways to take greater account of political considerations.
“Not just, but especially, in situations of overshoot, we need to start thinking about this as much as a physical process as a socio-political process…If we don’t do this, we are really missing out on some key uncertainties.”
Current scenarios used in climate research – including the Shared Socioeconomic Pathways and Representative Concentration Pathways – are “a bit quiet” when it comes to thinking about governance, institutions and peace and conflict, Gilmore said. She added:
“Political institutions, legitimacy and social cohesion continue to shift over time and this is really going to shape how much we can mitigate, how much we adapt and especially how we would recover when adding in the dimension of overshoot.”
Gilmore argued that, from a social perspective, adaptation needs are greatest “before the peak” of temperature rise – because this is when society can build the resilience to “get to the other side”. She said:
“Orthodoxy in adaptation [research] that you always want to plan for the worst [in the context of adaptation, peak temperature rise]… But we don’t really know what this peak is going to be – and we know that the politics and the social systems are much more messy.”
Dr Marta Mastropietro, a researcher at Politecnico di Milano in Italy, presented the preliminary results of a study that used emulators – simple climate models – to explore how human development might be impacted under low, medium and high overshoot pathways.
Mastropietro noted how, under all overshoot scenarios studied, both the drop to the human development index (HDI) – an index which incorporates health, knowledge and standard of living – and uncertainty increases as the peak temperature increases.
However, she said “the most important takeaway” from the preliminary results was around society’s constrained ability to recover from damage.
“This percentage of damages that are absorbed is always less than 50%. So, even in the most optimistic scenarios of overshoot, we will not be able to reabsorb these damages, not even half of them. And this is considering a damage function which does not consider irreversible impacts like sea level rise.”
Meanwhile, Dr Inês Gomes Marques from the University of Lisboa in Portugal, shared the results of an as-yet-unpublished study investigating whether the Lisbon metropolitan area holds enough public spaces to offer heatwave relief to the population under overshoot scenarios. The 1,900 “climate refugia” counted by researchers included schools, museums and churches.
Marques noted that most of the population were found to be within one kilometre of a “climate refugia” – but noted that “nuances” would need to be added to the analysis, including a function which considers the limited mobility of older citizens.
She explained that the researchers were aiming to “establish a framework” for this type of analysis that would be relevant to both the science community and municipalities tasked with adaptation. She added:
“The main point is that we need to think about this now, because we will face some big problems if we don’t”.
Legal implications and loss and damage
Significant attention was given throughout the conference to the legal considerations of the breach of – and impetus to return to – the Paris Agreement’s 1.5C warming limit.
This included discussions about how the international legal frameworks should be updated for an “overshoot” world where countries would need to pursue “net-negative” strategies to bring temperatures down to 1.5C.
There were also discussions around governance of geoengineering technologies and the fairness and justice considerations that arise from the real-world impacts of breached targets.
The conference was being held just months after the ICJ’s advisory decision that limiting temperature increase to 1.5C should be considered countries’ “primary temperature goal”.
IIASA’s Shleussner told Carbon Brief that the decision provided “clarity” that countries had a “clear obligation to bring warming back to 1.5C”. He added:
“We may fail to pursue it from below, but it doesn’t relieve us from the obligation to then pursue it from above.”
Prof Lavanya Rajamani, professor of international environmental law at the University of Oxford, insisted that “1.5C was very much alive and well in the legal world”, but noted there were “very significant limits” to what could be achieved through the UN Framework Convention for Climate Change (UNFCCC) – the global treaty for coordinating the response to climate change – both today and in the future.
Summarising discussions around how countries can be pushed to deliver the “highest possible ambition” in future climate plans submitted to the UN, Rajamani urged delegates to be “tempered in [its] expectations of what we’re going to get from the international regime”. She added:
“Changing the narratives and practices at the national level are far more likely to filter up to the international level than trying to do it from a top-down perspective.”
In a parallel session, Prof Christina Voigt, a professor of international law at the University of Oslo, pointed out that overshoot would require countries to aspire beyond “net-zero emissions” as “the end climate goal” in national plans.
Stabilising emissions at “net-zero” by mid-century would result in warming above 1.5C, she explained, whereas “net-negative” emissions are required to deliver overshoot pathways that return temperatures to below the Paris Agreement’s aspirational limit. She continued:
“We will need frontrunners. Leaders, states, regions would need to start considering negative-emission benchmarks in their climate policies and laws from around mid-century. There will be an expectation that developed country parties take the lead and explore this ‘negativity territory’.”
Voigt added that it was “critical” that nations at the UNFCCC create a “shared understanding” that 1.5C remains the “core target” for nations to aim for, even after it has been exceeded. One possible place for such discussions could be at the 2028 global stocktake, she noted.
She said there would need to be more regulation to scale up CDR in a way that addresses “environmental and social challenges” and an effort to “recalibrate policies and measures” – including around carbon markets – to deliver net-negative outcomes.
In a presentation exploring governance of solar radiation management (SRM), Ewan White, a DPhil student in environmental law at the University of Oxford, said the ICJ’s recent advisory opinion could be interpreted to be “both for and against” solar geoengineering.
Countries tasked with drawing up global rules around SRM in an overshoot world would need to take a “holistic approach to environmental law”, White said. In his view, this should take into account international legal obligations beyond the Paris Agreement and consider issues of intergenerational equity, biodiversity protection and nations’ duty to cooperate.
Dr Shonali Pachauri, research group leader at IIASA, provided an overview of the equity and justice implications that might arise in an overshoot world.
First, she said that delays to emissions reductions today are “shifting the burden” to future generations and “others within this generation” – increasing the need for “corrective justice” and potential loss-and-damage payments.
Second, she said that adaptation efforts would need to increase – which, in turn, would “threaten mitigation ambition” given “constrained decision-making”.
Finally, she pointed to resource consumption issues that might arise in a world of overshoot:
“The different technologies that one might use for CDR often depend on the use of land, water, other materials – and this, of course, then means competing with many other uses [of resources].”
A separate stream focused on loss and damage. Session chair Dr Sindra Sharma, international policy lead at the Pacific Islands Climate Action Network, noted that the concept of loss and damage was “fundamentally transformed” by overshoot – adding there were “deep issues of justice and equity”.
However, Sharma said that the literature on loss and damage “has not yet deeply engaged with the specific concept of overshoot” despite it being “an important, interconnected issue”.
Sessions on loss and damage explored the existence of “hard social limits” under future overshoot scenarios, insurance and the need to bring more factors into assessments of habitability, including biophysical and social-economic constraints.
Communication challenges and next steps
At the conference, scientists and legal experts collaborated on a series of statements that summarised discussions at the conference – one for each research theme and an overarching umbrella statement.
IIASA’s Schleussner told Carbon Brief that the statements represented a “key outcome of the conference” that could provide a “framework” to guide future research.
Nevertheless, he noted that statements are a “work in progress” and set to be “further refined” following feedback from experts not able to attend the conference.
At the time of going to press, the overarching conference statement read as follows:
“Global warming above 1.5C will increase irreversible and unacceptable losses and damages to people, societies and the environment.
“It is imperative to minimise both the maximum warming and duration of overshoot above 1.5C to reduce additional risks of human rights violations and causing irreversible social, ecological and Earth system changes including transgressing tipping points.
“This is required by international law and possible by removing CO2 from the atmosphere and further reducing remaining greenhouse emissions.”
Conference organisers also pointed delegates to an open call for research on “pathways and consequences of overshoot” in the journal Environmental Research Letters. The special issue will be guest edited by a number of scientists who played a key role in the conference.
Meanwhile, communications experts at the conference discussed the challenges inherent in conveying overshoot science to non-experts, noting potential confusion around the word “overshoot” and the difficulties in explaining that the 1.5C limit, while breached, was still a goal.
Holly Simpkin, communications manager at the Potsdam Institute for Climate Impact Research, urged caution when communicating overshoot science to the general public:
“I don’t know whether ‘overshoot’ is an effective communication framing. It is an important scientific question, but when it comes to near-term action and the requirements that an ambitious overshoot pathway would ask of us, emissions are what are in our control.
“We could spend 10 more years defining this and, actually, it’s quite complex…I think it’s better to be honest about that and to try to be more simple in that frame of communication, knowing that this community is doing a wealth of work that provides a technical basis for those discussions.”
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Overshoot: Exploring the implications of meeting 1.5C climate goal ‘from above’
As tech giants race to build out AI and the sprawling infrastructure it depends on, climate concerns have tended to focus on one thing: power-hungry data centres.
Their electricity use is growing so fast that by 2030, it’s projected to be nearly three times more than the combined annual consumption of Pakistan, Bangladesh and Nigeria. With the explosion in the construction of data centres driving new investment in fossil fuels, especially in the US, greenhouse gas emissions generated by data centres – now standing at less than 1% of the global total – are set to soar.
But this narrow focus on electricity has let AI’s supporters and the International Energy Agency (IEA) make a convenient case: that rising emissions can be more than offset by the technology’s green applications, like optimising renewables or boosting efficiency. That story conceals how AI’s real climate danger lies elsewhere: in the oil fields, where it’s helping fossil fuel companies extract planet-heating oil and gas faster and more cheaply.
As a senior manager at Microsoft, Holly Alpine was shocked by this blind spot. In 2024, she and her husband Will – also a Microsoft manager – quit their jobs and launched a campaign to hold Big Tech accountable for the emissions its technology enables.
Over the past two years, they have teamed up with two researchers to quantify just how deep the fossil fuel industry’s embrace of AI tools runs.
Their peer-reviewed study, published last week, found that when AI is adopted at similar rates across the fossil fuel and renewable energy sectors, the net effect is a rise in emissions of 0.47–1.8 gigatonnes of CO2 annually. That’s equivalent to Mexico’s annual emissions at the low end, and to Russia’s – the world’s fourth-largest emitter – at the high end. It is also 3.3 to 13.3 times higher than the emissions currently generated by powering AI data centres.
We spoke with Alpine about the risks of overlooking this side of the AI climate story and what can be done to shift the focus.
Q: Why has the climate conversation focused so heavily on data-centre power use when your modelling suggests that’s the smaller part of the AI emissions story?
A: It’s been quite unfortunate that it has been framed that way and that it has stuck so much because that framing is wholly incomplete, very misleading and is leading to very dangerous consequences.
It’s in the fossil fuel industry and the technology companies’ favour to frame the equation in this way because it leaves out any responsibility and accountability of the tech’s use by fossil fuel companies, which is a large part of their business. They’re some of their largest customers and they have teams of engineers and sales folks who are dedicated to the fossil fuel industry.
Simply comparing the power needed to run the technology and its [clean energy] applications is also kind of apples to oranges. On the one hand, you have real-world actual emissions and, on the other, hypothetical future avoidance of emissions as a result of potential future use cases for renewables.
What we are saying is that we need to look at both sides of the ledger for AI applications, renewables versus fossil fuels, and then also add the emissions generated by running data centers on top of it.
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Explainer: Will AI data centres make or break the energy transition?
As grids struggle to meet soaring electricity demand for AI data-crunching, big tech is under pressure to cover the costs of boosting power supplies – which may be dirty or clean
Q: How do AI applications help fossil fuel companies in a way that drives up emissions?
A: It’s everything from finding more oil and gas underground by processing hundreds of terabytes of seismic and well data that would otherwise have to be done manually. These AI models can process this data extremely quickly and create high-resolution images of what is underground. It helps companies pinpoint the oil and gas reserves that are most likely to be commercially recoverable.
Fossil fuel companies can identify and develop fossil fuel deposits with a lot more certainty, allowing them to move forward with projects that would otherwise have been too risky or too slow to pursue. AI makes them viable.
We’ve seen that rig counts [number of active drilling rigs] have dropped dramatically, so they need fewer resources to get out even more fossil fuels. Their costs are decreasing, while their production is increasing.
Q: How deep do these relationships run between Big Tech and fossil fuel companies? How do they compare with equivalent relationships with renewable energy companies?
A: I have to caveat that I have not worked for Microsoft for about two years. But what we saw at the time was that the fossil fuel-dedicated teams were much larger in terms of the number of employees, the size of the contracts, and the long-standing relationships.
This is not new. Microsoft has worked with the fossil fuel industry for many years and has deep partnerships, starting with the humble machine-learning going back many years. AI is just the latest wave of technology being applied in this way.
There are also relationships between the tech companies and renewables companies [and] battery storage developers. There are definitely sustainability-related applications of the technology.
One of the recommendations that we had given the company [Microsoft] was to shift the ratio of engineering resources from fossil to low and no-carbon energy sectors within the company. When they came out with their principles for engagement with the fossil fuel industry in 2023, they committed to shifting engineering resources. But then we did not see any actual change in business practices.
Q: Tech companies are now quietly scaling back some of their climate commitments, but there was a point, not long ago, when they wanted to be seen as climate leaders. Was there ever a genuine commitment to do that, or was it just an image they were projecting?
A: It depends on how you evaluate a company for its climate impact. If all we are looking is its own operational emissions, then in that case, Microsoft was and, still is to some extent, a climate leader.
But if we evaluate a company based on what it is producing, then I would say it’s a very different story. Back in 2019, ExxonMobil said it was able to produce an extra 50,000 barrels [of oil] per day purely thanks to Microsoft technology. There was also another public and quantified deal with Chevron.
We calculated that those emissions alone from just two deals among dozens were 300% of Microsoft’s entire operational emissions, including data centres. So, how do you want to evaluate your company?
If you look at other sectors and, say, evaluate a weapons manufacturer on its violence footprint, you don’t just look at their supply chain and the violence within it to create the weapons. You look at the real-world impact of the weapons they’re manufacturing. Yet we completely left technology companies off the hook.
Q: You make some recommendations as well in the paper. They include the idea of putting some supply-side constraints on this AI-enabled productivity for fossil fuel companies. What would that look like in practice?
A: Ultimately, our goal would be to have disclosure and governance measures that limit AI’s role in increasing fossil fuel productivity. The first thing would be a recognition of “enabled emissions” even as a measurable category because, at the moment, they are not included in any emissions disclosure or accountability frameworks.
Then we should require transparency around these fossil fuel contracts and constrain some of these specific mechanisms that the research identifies.
We are not trying to have a blanket ban on AI or even a blanket ban on AI use in the fossil fuel industry. There are some great applications, like methane leak detection, for example. But we just want to align applications with climate science and ensure that any contracts that move forward have been evaluated against a 1.5C future.
AI governance debate silent on risks to nature, campaigners warn
The easy thing would be for companies to voluntarily put guardrails on how their tech can be used, which is not new. There just currently are none for climate. But we do think that… policy is what needs to be implemented.
We also think that if we can change the market structure and incentives, then this kind of restriction will follow. If we look at ESG investing and how sustainable investing is defined, if we include what these companies are doing into that evaluation, then that can move capital flows.
Q: What do you think are the most promising avenues where you can shift the AI narrative and drive the change you are seeking to achieve?
A: We are now building off the study and there are various governance frameworks that we are attempting to incorporate this sort of evaluation into like the Greenhouse Gas Protocol or the Science Based Targets initiative (SBTi)
Luckily, we have seen some very promising drafts for the future of those frameworks that do include evaluations and disclosures of this work, which is really exciting.
The vote that stopped a data center: US communities query resource-hungry AI
We also need to look at companies for impacts in order to evaluate their sustainability metrics, and there could be potential greenwashing concerns that we could address on the legal side of things.
And then [there are] different policy workstreams. In the EU, we were quite hopeful about the AI Act,and the various use cases that were classified as high risk and would go through additional scrutiny. Unfortunately, with the Omnibus passing [in July], that opportunity is a little restrained.
But now with the Cloud and AI Development Act (CADA) coming out with various European frameworks around evaluating tech’s impacts, we hope to inform those discussions with this research.
The post “Dangerous consequences” – how AI’s climate framing lets Big Tech off the hook appeared first on Climate Home News.
“Dangerous consequences” – how AI’s climate framing lets Big Tech off the hook
Emissions from land-use change – including deforestation, loss of peatland and forest degradation – have been falling over the course of the 21st century.
The latest Global Carbon Budget report, formally published in May in the journal Earth System Science Data, notes a “statistically significant decrease” in land-use change emissions since the late 1990s.
The 21st-century decline in land-use emissions has accelerated in recent years, with the report highlighting a “steep drop” after 2015.
Writing for Carbon Brief in November 2025, climate scientists Dr Zeke Hausfather and Prof Pierre Friedlingstein noted that land-use emissions in 2025 had decreased by “around 32% compared to their average in the 2000s”.
Via six charts, Carbon Brief explores how – and why – land-use emissions have fallen over the past quarter of a century as fossil-fuel emissions have continued to climb.
How have land-use emissions changed?
Deforestation, forest degradation, loss of peatlands and harvesting trees for wood all release carbon into the atmosphere.
Collectively, these emissions are known as land-use, land-use change and forestry (LULUCF) emissions, referred to here as land-use emissions.
Each year, global land-use emission trends are analysed in the Global Carbon Budget report. The report, produced by dozens of scientists, documents how human-caused greenhouse gas emissions are changing over time.
Key findings from the annual report are released each year in the autumn, before being published formally in an academic journal the following year following a peer-review process.
(For more on the findings of the 2025 report, read Carbon Brief’s summary.)
The latest edition of the Global Carbon Budget report notes that, in the four decades to 1999, net CO2 emissions from land-use change remained “relatively constant”, sitting at around 6.6bn tonnes of carbon dioxide (GtCO2) per year.
However, since the late 1990s, global land-use emissions have been falling.
The 2025 report estimates that land-use emissions over 2015-24 averaged at 5GtCO2 a year. This is around 23% lower than the average over 1995-2004 and 19% lower than 2005-14, it says.
In contrast, global emissions from fossil fuels and cement have increased every decade since 1959, rising from an average of 11GtCO2 in the 1960s to 35.9GtCO2 over 2015-24, it says.
“Preliminary data” included in the report suggests that land-use emissions in 2025 clocked in lower than their 2014-25 average, at 4.1GtCO2, as fossil-fuel and cement emissions reached a new high of 38.1GtCO2.
(For more on how land-use emissions are calculated, see: Why are estimates of land-use emissions uncertain?)
The chart below shows how land-use emissions have been falling in the 21st century and have helped to temper the overall rise of human-caused emissions.
Why have land-use emissions fallen?
The Global Carbon Budget attributes falling land-use emissions since the late 1990s to decreasing emissions from deforestation, in particular “permanent deforestation”.
Permanent deforestation refers to the complete removal of trees for the conversion of forest to another land use, such as agriculture, mining or the construction of towns and cities. This sets it apart from other forms of deforestation, such as logging and rotational farming, where the canopy is removed on a more temporary basis.
The Global Carbon Budget also points to “increasing [CO2] removals” from forest regrowth as a reason for falling land-use emissions since the turn of the century.
(For more on the countries and policies that have driven these changes, see: Which countries are behind falling land-use emissions? and: Which countries are leading on forest regrowth?)
Looking at more recent trends, the report attributes a “steep drop” in land-use emissions in the decade since 2015 to the “combined effect” of a “peak” in peat fire emissions in 2015, as well as a “long-term decline” in deforestation emissions in many countries over 2010-20.
The chart below shows how deforestation and forest growth have been responsible for the bulk of change to land-use emissions over the 21st century.
Over 2015-24, the sequestration of CO2 through reforestation and afforestation efforts offset two-thirds of deforestation emissions, according to the Global Carbon Budget report.
Specifically, it notes that deforestation was responsible for an average of 6.96GtCO2 of emissions each year over 2015-24. Forest growth, on the other hand, removed 4.76GtCO2 a year.
Just under half – 2.2GtCO2 – of carbon removals over 2015-24 was from afforestation and reforestation efforts and the remaining 2.56GtCO2 were driven by forest regrowth from shifting cultivation cycles, it says.
Forest regrowth from shifting cultivation refers to the recovery of a forest after a plot has been farmed for a short period and then abandoned.
This is shown in the chart below below, which shows how carbon removals from forest regrowth have offset emissions from deforestation.
In the near-term, the Global Carbon Budget attributes its projection of a drop in land-use emissions between 2024 and 2025 to the “end of El Niño conditions”.
(The naturally occurring weather phenomenon typically leads to the drying out of peatlands in the tropics and causes more planned deforestation fires to burn out of control.)
Prof Pierre Friedlingstein, director of the Global Carbon Budget office and a professor at the University of Exeter, tells Carbon Brief there is “no indication” of what might happen in the future, but adds that land-use emissions trends over the 21st century are “going in the right direction”. He says:
“If you are optimistic, you hope the trend will not reverse and start increasing again. But we don’t know for sure. The assumption, given current land policies across the world, is that deforestation should continue to decline.”
Which countries are behind falling land-use emissions?
The countries that contributed the most to land-use emissions over 2015-24 were Brazil, the Democratic Republic of the Congo (DRC) and Indonesia, according to the Global Carbon Budget.
It notes that these three countries together contributed more than half – 57% – of global land-use emissions.
Over the first quarter of the 21st century, falling land-use emissions in Brazil and Indonesia have combined with increased afforestation and reforestation in China to drive down overall land-use emissions, according to the Global Carbon Budget.
This is illustrated in the chart below, which shows how China’s land-use emissions have dropped below zero, as Brazil and Indonesia’s emissions have declined.
Friedlingstein says that the decline in land-use emissions since the 2000s has been “primarily driven by a decline in deforestation in Brazil”.
He tells Carbon Brief that tree clearance in the South American country rose in the 1990s then started to fall after a peak in the 2000s:
“There was a bit of up and down – mainly due to politics and who was in charge in Brazil – [whether the president] was [Luiz Inácio] Lula [da Silva] or [Jair] Bolsonaro. But the long-term trend in Brazil is a decline in deforestation due to forest protection policies.”
These policies included a 2004 “action plan” for the prevention and control of deforestation in the Amazon, a 2006 soy moratorium, which banned the purchasing and financing of soya produced in deforested areas of the Amazon, as well as the expansion of protected areas across Brazil during the second half of the 2000s.
Prof Julia Pongratz, a professor of physical geography and land-use systems at the University of Munich and contributor to the Global Carbon Budget, says Brazil is the “single most important contributor to the early-2000s global land-use change emissions peak and subsequent decline”.
She says that the largest contributor to an “acceleration” in the decline of global land-use emissions in the past decade has been Indonesia, which she notes has “rewetted more peatland area since 2017 alone than Europe in its entire history”.
Around the world, peatlands are exploited and damaged by humans for a range of purposes, including converting the land for agriculture and peat extraction for horticulture and fuel. Peatland wetting refers to the process of restoring water levels in drained peatlands in order to return them to their natural, waterlogged conditions, which allows for peat formation and carbon storage.
Another reason for Indonesia’s downward trend in land-use emissions is that there have been fewer spikes in emissions caused by fires related to human land-use activities over the last decade, says Pongratz.
Emissions from ecosystem fires are not always counted towards national and regional land-use emissions budgets, which estimate the sum of human-caused emissions. Deforestation fires and those related to peatland drainage are included, whereas fires caused by droughts and heatwaves are not.
Pongratz says it is “hard to separate natural and land-use drivers completely”, given that deforestation and peatland fires often “get out of control and cause spikes in emissions” during dry El Niño conditions.
(For more on uncertainties in land-use emissions data, see: Why are estimates of land-use emissions uncertain?)
Pongratz notes that international trade regulations that have helped to drive down land-use emissions in Brazil and Indonesia have had a lesser effect in the DRC, where the root drivers of deforestation are different:
“Emissions in the DRC have increased, then stayed high in the last two decades. This is partly related to population growth and expanding smallholder and subsistence farming.
“The picture is different in Brazil and Indonesia, which are much more driven by export; international regulations aiming at curbing deforestation thus have larger effects in these countries.”
Which countries are leading on forest regrowth?
Reforestation and afforestation schemes that draw down carbon from the atmosphere have helped to reduce the overall emissions from land-use change over the course of the 21st century.
As noted above, the 2025 Global Carbon Budget report highlights how the removal of carbon from forests offset two-thirds of deforestation emissions over 2015-24.
The report says that China, the EU and US account for the highest levels of carbon sequestration from reforestation and afforestation, collectively drawing 1.1GtCO2 per year over the 2015-24 period.
This, it says, is “partly related to expanding forest area as a consequence of the forest transition in the 19th and 20th centuries and subsequent regrowth of forest”.
The chart below, which draws from the latest edition of the “state of carbon dioxide removal” report, shows how carbon uptake by forests has increased over the last 20 years in a number of countries, most notably in China.
by country, 2005-24. Data from 3rd “state of carbon dioxide removal” report (2026). Chart by Carbon Brief.
In China, a raft of reforestation and improved land management policies were introduced in the 1990s which have led to the rehabilitation of tens of millions of hectares of forests. Research has shown the schemes have significantly increased the country’s uptake of carbon and switched its land from a carbon source to a carbon sink.
The Global Carbon Budget highlights that substantial carbon removal from reforestation and afforestation occurred in other regions, such as Brazil, Russia and Indonesia. However, in these regions, emissions from deforestation and other land-use changes “dominate”, it says.
Why are estimates of land-use emissions uncertain?
Tallying the world’s emission from land-use change is complex.
The Global Carbon Budget estimates an uncertainty range of 2.6GtCO2 per year for its average annual global land-use emissions figure for 2015-24 – more than half the overall figure of 5GtCO2.
To calculate overall land-use emissions for the annual Global Carbon Budget report, researchers create an average from three land-use models: BLUE, OSCAR and LUCE.
These models combine satellite and statistical information on land cover and land-use changes from global and regional datasets.
Pongratz, who is involved in the LUCE model, explains that scientists can measure the exchange of CO2 between land and atmosphere, but are not able to determine whether CO2 is being released or sequestered from a managed area as a result of human activities or other climate or environmental factors. She continues:
“For this, you need to turn to modelling, where you can isolate drivers – and, again, models are uncertain and the land-use input imperfect. This is why we use all available model estimates – three at the moment.”
The Global Carbon Budget highlights that its three different models treat different components of the land-use emissions “budget” differently.
While models agree “relatively well” about emissions from permanent deforestation, they take different approaches in their approach to shifting cultivation patterns, which increases both emissions and removals, as well as wood harvesting, it says.
Moreover, it notes that land-use emissions and removals occur on different timelines. While carbon removals generated by forest growth and soil recovery are “slow”, there is an “instantaneous component” to emissions from deforestation, it says.
(For more on the challenges in analysing changes to the global carbon cycle, see Carbon Brief’s recent in-depth interview with Prof Philippe Ciais, one of the world’s leading experts on land-use emissions.)
The Global Carbon Budget notes that its confidence in its 2025 projection for overall land-use emissions remains “low” given that the figure is based on deforestation, degradation and peat fire emissions, which are “only a proxy” for land-use change.
The report notes that 2023 is the final year in which it calculates land-use emissions directly from land-use statistics across all three bookkeeping models. For more recent years, full statistics are not yet available across the models and scientists instead turn to short-term proxies.
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The post Why land-use emissions have fallen by a third this century – in six charts appeared first on Carbon Brief.
Why land-use emissions have fallen by a third this century – in six charts
After a five-year long legal battle, the Constitutional Court of South Africa has blocked Shell and local partner Impact Africa’s permit to explore for oil and gas off the country’s East Coast, in a landmark victory for local communities and civil society.
“Today’s judgment makes me feel very happy and proud that the ocean is not for profit for mining companies,” said East Coast resident and environmental campaigner Siyabonga Ndovela.
The verdict culminates a years-long process in which non-profits Sustaining the Wild Coast, Natural Justice, Greenpeace Africa, and others took legal action against Shell, Impact Africa and the South African government for failing to consult affected communities – a legal requirement in the country.
The Constitutional Court ruled that Shell and Impact Africa had not complied with resource governance law, had failed to meaningfully conduct public consultation and had failed to consider the impact on climate change, cultural rights, livelihoods and ecological harm.
The ruling references last year’s landmark advisory opinion by the International Court of Justice, which states that countries have a legal duty to prevent and repair damage to the climate system. The South African judges argued climate change “transcends borders” and that states’ obligations “must be understood within the broader framework of international law.”
“This case must also be understood against the backdrop of well-documented struggles by coastal communities to protect their land, marine resources and ways of life in the face of extractive activities that they believe threaten their very existence,” wrote Justice Narandran Kollapen.
The Constitutional Court found that the exploration right had been unlawfully granted by the Department of Mineral and Petroleum Resources.The ruling upholds a 2022 regional court decision against Shell and overturns a 2024 appeal that allowed the company to conduct fresh public consultations under the original exploration right. Today’s decision means the right, initially granted in 2014, must be set aside.
Celebrating the decision, Sherelee Odyar, oil and gas campaigner at Greenpeace Africa, told Climate Home News that the court confirmed “serious failures” in the awarding of exploration rights to Shell and Impact Africa, which “can not simply be corrected later”.
The Wild Coast is a biodiversity hotspot which has been conserved over generations by coastal communities who rely on the ocean and land. “Our land and sea are central to our livelihoods and our way of life. Over generations we have conserved them, and they have conserved us,” reads the founding statement in the case.
A Shell spokesperson said it noted the ruling, responding that “we are committed to responsible offshore exploration, meaningful stakeholder engagement and environmental stewardship.”
The Department of Mineral and Petroleum Resources did not respond to requests for comment at the time of publication.
“Renewed strength” for communities
The ruling adds to a series of legal challenges brought by civil society groups against oil companies and the government as South Africa has expanded oil and gas development since 2014 under Operation Phakisa, a plan aimed at “unlocking the economic potential of the oceans”.
On the West Coast, Walter Steenkamp, Chair of Aukotowa Fisheries Cooperative, which is involved in a separate ongoing legal action against TotalEnergies, said that “today’s court case gave me renewed strength.”
The case could also set a precedent for future oil developments, said Alessandro Mazzi, legal governance researcher at the University of Wageningen. He added that the verdict “sends a strong signal to investors that where projects affect people’s land, livelihoods and environment, meaningful consultation and genuine ecological assessment are an integral part of responsible investment”.
Janet Solomon, coordinator of advocacy group Oceans not Oil, said that the Court’s emphasis on democratic participation, culture, livelihoods and the health of future generations in handing down the verdict signals a shift in jurisprudence on environmental governance, saying that this focus “may prove to be the judgment’s most enduring legacy.”
The post South Africa’s top court blocks Shell’s offshore oil exploration right appeared first on Climate Home News.
South Africa’s top court blocks Shell’s offshore oil exploration right
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