Hundreds of scientists gathered in Oxford last week to discuss the many different ways of removing carbon dioxide from the atmosphere and the role it can play in tackling climate change.
The third international conference on negative CO2 emissions focused on the latest science, policy gaps and methods of carbon dioxide removal (CDR). (Carbon Brief also reported from the first conference in Gothenburg in 2018.)
Discussions ranged from the potential of different technologies to the need to avoid CDR methods drawing attention away from emissions reductions.
Around 360 scientists, researchers, industry representatives and other stakeholders attended the four-day event at the University of Oxford, along with more than 150 people online.
Talks centred on the “natural” and “novel” ways to take CO2 from the atmosphere and store it on land, underground or in the ocean.
Carbon Brief attended the conference to report on the dozens of plenaries and parallel sessions that focused on a wide range of issues around CO2 removal.
Smith is the lead author on the second “State of CDR” report, which outlines the current state of knowledge around CDR, and used his talk to outline some of its findings. (Read Carbon Brief’s nine key takeaways from the report here.)
Smith explained that “conventional” CDR – mainly through land use, land-use change and forestry activities – make up the “lion’s share” of current CDR efforts, accounting for almost all of the current 2bn tonnes of CO2 removed from the atmosphere each year. (Humans emit around 40bn tonnes each year.)
“Novel” CDR methods currently remove a much-smaller 1.3m tonnes of CO2 each year – less than 0.1% of total carbon dioxide removals – he noted.
Of the novel approaches, he explained that biochar is the main player. This is followed by bioenergy with carbon capture and storage (BECCS), which is confined to “essentially two plants in the US”.
All other CDR efforts, such as direct air carbon capture and storage (DACCS) are a “tiny, tiny sliver”. This breakdown is outlined in the graphic from the report below.
“Conventional” CDR (grey shading) compared to “novel” (yellow and black) methods. Source: Smith et al. (2024) executive summary.
Smith noted that almost all current model simulations that limit future warming to 1.5C above pre-industrial levels use CDR methods such as BECCS.
However, he said that many models – such as those that feed into reports from the Intergovernmental Panel on Climate Change (IPCC) – begin their projections from the year 2020. Many models assume that emissions already peaked in 2020, but emissions today are continuing to rise. Smith warned:
“We are already overshooting.”
Speaking to Carbon Brief at the conference, Smith said that there is a “tension” between fast and responsible action to scale up carbon dioxide removals. He added:
“People are seeing the urgency of the climate problem and saying we need to scale lots of things now and fast.
“So probably the basic biogeochemical principles are sound, but [an important step is] actually measuring how much carbon is taken up, how quickly and what are the broader impacts on the environment and on people.”
In a separate session, experts discussed “measurement, reporting and verification” – ways to assess methods of CDR technologies to ensure they are working effectively. This is similar to discussions around monitoring the voluntary carbon market. (See Carbon Brief’s special series on carbon offsetting for more.)
Dr Paul Zakkour from Carbon Counts, a climate and energy consulting company, opened the second day of the conference by discussing the importance and challenges of monitoring, reporting and verifying claims about CO2 removals.
Zakkour said the most important principles for any carbon removal carbon credits are ensuring that they are real, measurable, additional, not double counted, not leaking and permanent.
He said there are more than 50 methodologies crediting “natural” methods of CDR such as forest management and soil organic carbon.
There are around 20 methodologies for novel CDR methods. Almost all of these methodologies were developed in just the past three years, he said.
However, he added that it is unclear how many projects are actually using these methodologies to enter voluntary carbon markets.
Zakkour noted that there is a “compromise” between ramping up carbon removals and ensuring they are done effectively, safely and in line with best scientific practices.
Over the four-day conference, there were dozens of breakout sessions discussing different CO2 removal techniques, ranging from bioenergy with carbon capture and storage (BECCS) to enhanced rock weathering. Carbon Brief focuses on a few of the methods here:
Forestry
Among the land-based CDR methods, forestry was a major point of discussion.
Dr Yuan Yao from Yale University discussed her ongoing research into sequestering carbon through afforestation and reforestation on “marginal land” in Brazil. Her research team examined the CO2 impacts of “innovative forest mosaics”.
Xueyuan Gao from the University of Maryland, whose research is currently under peer review, developed a novel framework to try and detect tropical tree cover gains, using forest management and cover change datasets. The study particularly focused on former agricultural lands.
At a separate session focused on Earth system modelling, Prof Julia Pongratz – a group leader at the Max Planck Institute for Meteorology – told the conference that modelling studies on large-scale afforestation and reforestation often involve “unrealistic” or “unambitious” spatiotemporal patterns.
Pongratz presented a pattern of afforestation and reforestation that she and her team developed. The pattern is aligned with “ambitious” country pledges and would result in 600m hectares of afforested/reforested land by 2060, while staying in line with “biodiversity and techno/socio/economic considerations”, she said.
This level of afforestation and reforestation would capture enough CO2 to offset global warming by 0.2C by the end of the century, Pongratz told the conference.
And at another session, Dr Clemens Schwingshackl, a researcher at the Ludwig Maximilian University of Munich, presented results from the state of CDR report on afforestation and reforestation. He explained that CDR from these two sources currently capture around 2,000m tonnes of CO2 (MtCO2) per year – equivalent to around 5-6% of current fossil fuel emissions.
He added that there are “hotspots” of tree planting. The main one is in China, where there are lots of forest plantations, he explained. And the other is in Europe, where a long history of deforestation is now being reversed in many areas.
Dooley, who is lead author on the report, explained that 194 countries were assessed and that, collectively, their afforestation, reforestation and BECCS pledges require one billion hectares of land. This is an ”unprecedented” amount of land-use change, which could increase risks to ecosystems, food security and the durability of carbon stocks, she warned.
She added that 70% of the total land required by these climate pledges comes from just a few, high-emitting countries.
Bioenergy with carbon capture and storage
Another session focused on bioenergy with carbon capture and storage (BECCS), a technology where plants are burned for energy and the resulting CO2 emissions are captured from air and stored under land or sea.
Her research shows that using biomass with a “low carbon footprint” and reducing supply chain emissions can help to maximise the overall CO2 removals of BECCS. She said that this is important in ensuring that the technology is implemented correctly, noting:
“You can do BECCs badly and end up emitting more CO2 than you can capture.”
He said that a “significant challenge” with BECCS is producing enough wood and other types of biomass to burn for the technology.
He and other researchers are looking at the technical barriers to scaling up biomass crops, trialling different plant options such as miscanthus. Another issue around increasing growth of biomass crops is incentivising farmers to grow them, he said, adding:
“How do we get these to be seen as a more usual option for farmers?”
Dr Sabine Egerer from the Ludwig Maximilian University of Munich discussed research looking at the different levels of efficiency of various land-based CO2 removal methods, namely afforestation and planting biomass crops for use in CDR technologies.
This research, which is currently undergoing peer review, finds that biomass plantations are more efficient at removing carbon from the atmosphere over time. But this varies in different parts of the world, such as China where afforestation has more benefits.
Her findings show that using agricultural residues for BECCS has more benefits for carbon removal overall compared to residue recycling, per tonne of biomass.
He looked at more than 130,000 species globally, and mapped how afforestation and BECCS would change biodiversity refugia – habitats that are less prone to extreme changes in environmental conditions than surrounding areas, and which often act as safe havens for species.
He showed that the impacts of land-based CDR are unequally distributed, mainly falling on countries in the global south.
There were also two conference sessions on direct air carbon capture, in which scientists discussed technological developments and the different engineering challenges that face the sector.
Soils and biochar
The ability of soils to sequester carbon from the atmosphere was a key discussion point at the conference. There was also a session on biochar – charcoal that is added to soils rather than burned as a fuel.
CO2 equivalent: Greenhouse gases can be expressed in terms of carbon dioxide equivalent, or CO2e. For a given amount, different greenhouse gases trap different amounts of heat in the atmosphere, a quantity known as the global warming potential. Carbon dioxide equivalent is a way of comparing emissions from all greenhouse gases, not just carbon dioxide.
CO2 equivalent: Greenhouse gases can be expressed in terms of carbon dioxide equivalent, or CO2e. For a given amount, different greenhouse gases trap different amounts of heat in the atmosphere, a quantity known as… Read More
Smith said the research is not expected to yield “big shifts in the cost and potentials” of these methods, but it aims to provide deeper analysis on the co-benefits and trade-offs of each method.
He added that previous research has found there is a potential to remove 5bn tonnes of CO2-equivalent (GtCO2e) each year from soils.
Dr Jeewani Peduru Hewa from Bangor University discussed ongoing research on greenhouse gas removals through peatland restoration, including applying biochar to peatlands.
A number of universities and NGOs are working together to restore different peatland sites across the UK to assess whether “innovative” land management can secure long-term greenhouse gas removal systems, she said, noting:
“When peatlands are healthy they are good for carbon sequestration. But if we drain the peatlands for agriculture or something else, it is a problem.”
Rewetting peatlands helps them to absorb carbon dioxide, but this can also cause methane emissions to rise. Her experimental research findings show that applying biochar to peatlands can lower both CO2 and methane emissions.
These findings were concluded over the course of one year and further research is needed to assess impacts over a longer time period, she said.
Marine CO2 removal
Removing carbon through the ocean was another significant discussion point at the conference.
Speaking in a plenary session on measuring, reporting and verification, Prof David Ho from the University of Hawaiʻi at Mānoa said that marine carbon removal still has many challenges to overcome before it is feasible on a wide scale.
Assessing this type of carbon removal is “challenging” due to the ocean’s natural variability, carbonate chemistry, ocean mixing and circulation, Ho said. It is difficult to pinpoint one specific reason for a change or an increase in CO2 sequestration.
Ho said that “abiotic” methods of marine CO2 removal are “easier” to monitor, report on and verify. These include ocean alkalinity enhancement. Last month, the carbon removals registry Isometric said it released a “world first” protocol for ocean alkalinity carbon removal.
Asked by an audience member about whether marine CO2 removal should be excluded from carbon markets due to the level of uncertainties, Ho said the ocean has the “potential” to make an impact, but advised caution. He added:
“I think if we can do a good job of quantifying the uncertainties…this is how ramp-ups can work. If buyers and sellers can trust each other, I think the ocean can certainly play a role.”
She highlighted public opinion, political dynamics, the “performance” of science and pressure from industry as key conditions that will drive policy developments in marine CDR.
She found that more than 80% of people in Germany and Canada had never heard of marine CDR, compared to 28% and 41% in Taiwan and China, respectively. She added that people are least likely to have heard of ocean acidity enhancement and most likely to have heard of marine-based BECCS.
The conference heard from a number of researchers about the role of government in regulating CO2 removal, including a plenary panel session dedicated to the topic of CDR in national policymaking.
Henderson said that a government’s role is to fix market failures through regulation and deregulation, and to be stewards of the environment. However, he noted that governments cannot easily regulate the voluntary carbon market and said it should “try to get more engaged” – for example, by implementing monitoring, reporting and verification measures.
He added that the voluntary carbon market is “not trusted” by many people, but argued that it is important to keep the market going, to enable experts to try things out and eventually build a more trusted system.
Speaking on national policies, he said that countries are “not quite there yet” and argued that CDR measures should be included in countries’ nationally determined pledges under the Paris Agreement.
Dr Fabiola Zerbini, director at the department of forests at Brazil’s Ministry of the Environment, told the conference that the country has pledged to restore 12m hectares of deforested land and reach “zero deforestation” by 2030.
The role of the government as a “catalyst” for this type of action is “key”, she said. She argued that until forests and the environmental services that they provide are considered to have “real value”, the system will need to be regulated by governments.
She also talked about how the fossil fuel companies responsible for extraction could play an important role in CDR:
“It could be interesting for the energy companies responsible for resource extraction to realise they could leverage their structures to put carbon back into the ground. [We] need to steer energy companies so that when they put infrastructure in, it can be used for CDR.”
When asked about the upcoming US election, she said that the administration has put frameworks in place that will make their work sustainable and so she did not think that a Republican victory would cause all current projects to be “erased”. However, she did express concern about whether measures would be kept in place to make sure that the projects “benefit people”.
Dr Fabien Ramos, carbon removals lead at the European Commission, talked about policies that the EU is putting in place to monitor and verify CDR in its emission trading system, and the regulations being put in place to assess the quality of carbon offsets.
Smith analysed the national climate strategies of 71 counties, and found that only 26 of them quantify residual emissions at the time of reaching net-zero emissions.
He noted that countries define their own residual emissions and found that the percentage of a country’s peak emissions that it considers “residual” can range from 5% to 50%.
He also explained that despite making up the majority of residual emissions, agricultural emissions are “hardly mentioned as residual”. Industry sources are mentioned the most, he found.
“Carbon farming” – farm practices focused on climate mitigation – may be one way to bridge the gap between the EU’s “ambitious targets” to cut agricultural emissions and the reality of these cuts so far, he said.
His research showed a number of ways to make carbon farming more attractive than conventional methods: subsidising costs of CDR measures, implementing CDR requirements on state-owned lands and excluding conventional practices on state-owned land.
The best solution, he said, is a mix of payment for public goods that avoid adverse environmental effects and bridging knowledge gaps among farmers and other landowners.
Kujanpää said that his research points to geological storage as a “key solution” for CO2 removal in Finland, but noted that the country currently has no national policy measures for this type of CO2 storage.
The study, published in Nature Climate Change, found that plans to “draw down” CO2 from the atmosphere “fall short” of the quantities needed to limit global warming to 1.5C above pre-industrial levels.
Assessing a range of scenarios for limiting warming to 1.5C, the authors found a “CDR gap” in 2050 of 0.4bn-5.5bn tonnes of CDR per year.
To fill this gap, Lamb said there is a need to identify and quantify country plans around CDR as nations are currently not required to specify these removals in the national plans submitted at COP climate summits.
He highlighted that there are differences in the land-use sector carbon emissions in national inventories and scientific models. (This was covered in more detail in a Carbon Brief guest post last year.)
Most countries only include plans about conventional, land-based CDR methods in their national plans up to 2030, Lamb explained. Some long-term emissions reduction plans include novel techniques such as BECCS.
Gidden said there are a number of differences between the models and inventories, including how countries define their “managed land” and carbon fluxes.
His research, published in Nature last year, aligned the IPCC mitigation pathways with national greenhouse gas inventories to allow a direct comparison. The findings suggested that key emission-cutting goals are “harder to achieve” than currently outlined and that countries would have to reach net-zero emissions sooner than 2050.
These findings highlighted the importance of focusing on both natural and novel CDR methods, but also mentioned the need to keep dependence on CDR “to a minimum”.
Koponen said the findings also show that existing EU CDR policies “are not sufficient for deep emission reductions”.
The report – put together by almost 70 scientists and 13 institutions – looks at regional possibilities for CDR and storage. Pett-Ridge said the US can reduce 1bn tonnes of CO2 from the atmosphere each year by 2050 using CDR methods, at an annual cost of $129bn.
She said it is sensible to initially focus on forestry and soils. Biomass conversion also has big potentials, she added. The researchers also analysed issues in inequity and justice as part of their analysis.
Meanwhile, Prof Kirsten Zickfeld – a professor of climate science at Simon Fraser University – discussed the global temperature response to CDR. She simulated 100GtCO2 of CDR from the atmosphere and calculated how atmospheric CO2 levels changed as the Earth system re-equilibrates.
She then modelled how the temperature of the planet would change in response. Comparing 100GtCO2 of CDR with a simple 100GtCO2 reduction in global emissions, she found that they probably do not have equivalent effects on global temperatures.
However, she says that due to the uncertainty in the models, it is unclear whether carbon removal drives a greater or smaller change in global temperatures than the same amount of reduced CO2 emissions. (Zickfeld explains more about this “asymmetrical” response in a Carbon Brief guest post from 2021.)
Edwards noted how difficult it is to predict the uptake of CDR over the coming century and explained the dangers of scenarios in which politicians rely on high CDR deployment, only for its rollout to be much lower than expected. She concluded that the most robust strategy is “planning for the worst and hoping for the best”.
Finally, Tabea Dorndorf, a doctoral researcher at Potsdam Institute for climate impact research, discussed the relative advantages and disadvantages of biochar, BECCS, DACCS and enhanced rock weathering. She explained that in a “middle of the road” scenario, it is likely that BECCS will be the biggest player, due to its higher carbon and biomass efficiency.
One of the main concerns around CDR is that promoting negative emissions technologies might draw attention away from the need to reduce emissions – a phenomenon known as “mitigation deterrence”.
The final day of the conference addressed this concern in a plenary session called, “How do we ensure CDR supports emission reductions instead of slowing them?”, chaired by Dr Holly Buck – an assistant professor from the University at Buffalo.
To open the session, Buck invited the conference attendees to fill in a poll, asking how concerned they are that CDR could slow down emissions reductions, and how concerned they are that mitigation deterrence could slow down CDR development.
The results, shown below, show that conference attendees were generally more concerned about the former than the latter.
A poll presented to the audience during the panel discussion.
The panel agreed unanimously that CDR is not a substitute for cutting emissions and that it should only be used for hard-to-abate or “residual” emissions.
Dr Zeke Hausfather, climate research lead at the financial technology company Stripe, warned that if society does not cut emissions, even a “wildly successful” CDR effort will still only reduce global warming from 2.7C to 2.6C by 2100, so mitigation is still crucial. (Haufather is also a climate science contributor for Carbon Brief.)
He added that mitigation deterrence in private companies is one of the main problems with CDR, explaining that it is almost always cheaper for companies to buy a carbon offset than to take action to reduce their own emissions, saying that the low price of CDR offsets do not reflect their true value. (See Carbon Brief’s special series for more on carbon offsets.)
This means that companies are more likely to buy CDR offsets than decarbonise their own industries, Hausfather said, warning that this “lets companies off the hook” on reducing their own emissions.
He told the conference that to correct for this, governments need to “play a much more active role” in regulation.
Hausfather also argued that “in a world in which CDR didn’t exist, global emissions would not be much different,” saying that in his view, the reason people are emitting today is not because they are banking on CDR, but because mitigation is too expensive.
He said there has been plenty of “much-needed” criticism of carbon offsets, highlighting an investigation into Verra carbon offsets, which found that more than 90% are “worthless”.
However, he noted that part of the response to criticism has been a “large-scale retreat by companies” of all types of offsets – including those which are “good”. He said that the negative emissions community needs to be clear about what companies should do, as well as what they shouldn’t.
He called it “suspicious” that governments and companies seem “very optimistic about CDR while very pessimistic about mitigation”. He warned that “CDR optimism sits very comfortably alongside a lack of ambition for phasing out fossil fuels” and called it “a way of avoiding politics”.
Dr Sara Nawaz, a researcher at the University of Oxford, shared concerns that companies are responsible for defining their own residual emissions and could define them in the way that best suits them.
Nawaz also noted the danger that CDR could lead to “competition with other resources that are needed for mitigation, for example land, water and energy”. She also told the conference that CDR can “bake in” an “equivalence” between CO2 emissions and removals that may not exist.
Hausfather said that the Science Based Targets Initiative (SBTi) – a “corporate climate action organisation” have “got the framework right” by suggesting separate emissions and removals targets. (The SBTi recently got into hot water over its stance on carbon credits.)
Hausfather also highlighted the problem of greenwashing, telling that audience that he worried that companies would spend some money implementing some CDR, but then spend vast amounts more money publicising it.
Hausfather also noted the tendency for models to be over reliant on CDR. He explained that in many model simulations, global temperatures overshoot key thresholds early in the century and then CDR is used to bring temperature back down later in the century. Models are “far too cavalier about overshoot”, he said.
In the penultimate plenary session of the conference, Prof Sabine Fuss from the Mercator Institute presented the initial stages of a “systematic review ecosystem on CDR”.
She explained that there has been “exponential growth” in literature on CDR, with some 23,000 papers included in the latest IPCC assessment cycle alone.
Hundreds of experts – including many scientists in the conference room – are working to synthesise this literature, Fuss said. She explained that the team has already grouped the studies into “clusters” of different CDR methods and developed a shared protocol so that methods and definitions are consistent across the groups.
For each cluster, an expert-led review team will work to produce an “in-depth paper”, Fuss said. A few group leads presented the early stages of their work.
There are around 2,000 papers on BECCS to review and more than 2,000 for a cross-cutting topic on “monitoring, reporting and verification”, the respective leads of these teams said.
Dr Finn Muller-Hansen is a researcher at the Mercator research institute and head of a cross-cutting group on public perceptions to CDR. He explained that most of the 165 papers in this area of research are focused on western countries. Most studies showed low awareness of CDR and mixed or positive attitudes towards different methods, he found.
He also outlined the main factors that affect peoples’ opinions of CDR, including the perceived “naturalness” of the method, trust in institutions and perceived risks and benefits of each method.
In the final session of the conference, former Conservative MP and chair of the COP26 climate summit Alok Sharma addressed the attendees. He said that “governments are not acting quickly enough” to tackle CO2 emissions, adding:
“I think that we need to be doing everything very quickly. I don’t think there is some sort of divide between trying to take CO2 out of the atmosphere and doing more in terms of renewables…The pace isn’t fast enough.”
Film director and producer Leila Conners also spoke to conference attendees about her upcoming documentary Legion 44, which focuses on CDR technologies.
This is part of her film trilogy that also included the 11th Hour, a documentary featuring actor Leonardo DiCaprio.
Speaking to Carbon Brief about the range of discussions at the four-day conference, Dr Steve Smith said the discourse has changed since the first negative CO2 emissions conference in 2018. He told Carbon Brief:
“There’s a wider range of methods being looked at and a broader range of disciplines being brought to bear to look at this issue…Policymakers in particular are starting to move on this issue.”
Smith noted that in future, countries “may well need a lot of carbon removal as well as cutting emissions”. He added:
“For me, it’s not really emphasising just the trees or just the technologies. But we have a range of options and we should be exploring all of them at the moment.”
The next negative CO2 emissions conference will be held in Vienna, Austria in 2026.
KOROR, PALAU, Monday 31 August 2026 — As Pacific leaders gather for the 55th Pacific Islands Forum Leaders Meeting in Palau from today, Greenpeace Australia Pacific is urging Prime Minister Anthony Albanese to stand with Pacific family by keeping Pacific needs at the heart of negotiations, backing longstanding Pacific leadership, supporting Pacific energy sovereignty and ocean custodianship, and holding the line on 1.5°C.
Against the backdrop of tense geopolitical turmoil, increasingly frequent and lethal extreme weather disasters, the threat of deep sea mining and an energy crisis driven by fossil fuel dependence, the Pacific Islands Forum Leaders Meeting (PIFLM) is a critical moment for Pacific nations to unite with Pacific needs central to regional dialogue.
The climate crisis, security, the opportunities of renewable energy in the Pacific, ocean protection, and the shifting political landscape will be the focus of the Forum’s discussions.
Speaking from Palau, Shiva Gounden, Head of Pacific at Greenpeace Australia Pacific, said: “The Pacific Islands Forum is the most important multilateral forum in our region, unifying the Pacific under increasingly turbulent global circumstances. We are urging Forum members, including Australia, to not lose focus of Pacific priorities of climate and oceans amid noise and external pressures at this year’s meeting.
“It is very clear that the greatest security threat to our region is climate change and the only way we can address that is through a just transition away from fossil fuels. Regional cooperation is an antidote to climate chaos and geopolitical tension – together, our region can be guided by Pacific nations’ legacy of leadership from the frontlines of the climate crisis, as we build a more peaceful and secure world.
“This year’s Forum will set the stage as we build momentum toward COP31 and a Fossil Fuel Free Pacific. Australia must back Pacific energy sovereignty as a solution to the compounding threats facing our region, including soaring costs of living and increasingly lethal extreme weather disasters, and resist the militarisation of our oceans, deep sea mining, and power politics.
“We must not lose sight of what is needed. The regional adoption of Pacific-led solutions, a Pacific pre-COP with focus on advancing the just transition away from fossil fuels and community-targeted finance for strong and resilient futures beyond fossil fuels must be the foundations of this year’s Forum discussion. What we need now is stronger political will.”
Also in Palau, Dr Simon Bradshaw, COP31 Lead and climate expert at Greenpeace Australia Pacific, said: “Prime Minister Albanese faces a major test of Australia’s climate credibility and Pacific partnership this week. We cannot be a friend to the Pacific and continue to expand fossil fuel production. The best way for Australia to remain the Pacific’s security partner of choice is to act faster on the Pacific’s number one security concern — climate change.
“The Albanese Government has approved at least five new coal and gas projects since the last Pacific Islands Forum Leaders Meeting, and 36 since being elected, every one of which increases the threats to life, security and sovereignty facing Pacific communities.
“Nowhere in the world are the dangers of fossil fuels or the benefits of renewable energy clearer than in the Pacific, which faces the double blow of climate disasters and expensive fuel imports.
“Australia, as incoming President of Negotiations for COP31, has a responsibility to follow the Pacific’s lead, embrace the vision of a resilient Fossil Fuel Free Pacific, and do everything possible to keep 1.5°C alive. Doing so would establish Australia as a highly effective middle power, a force for good in troubled times, and a true ally and partner to the Pacific.”
—ENDS—
Greenpeace Australia Pacific has delegates from the Pacific and Australia at the PIFLM in Palau available for interview
Every six to seven years, climate modelling groups around the world run a coordinated set of simulations that explore how the climate could change in the future.
The new scenarios are quite different from their predecessors in a number of notable ways.
Rather than being named, somewhat enigmatically, according to their “radiative forcing levels”, the new scenarios are named simply by their emissions trajectories – ranging from “low-to-negative” to “high”.
They no longer consider “no-climate-policy” baseline worlds, but instead explore the implications of current policies continuing, being strengthened, or weakening.
These new scenarios also dramatically revise high-end future emissions downward, far below the highest scenarios in prior generations, in order to reflect a world where a 21st century dominated by coal use is no longer plausible.
At the same time, they revise the lowest emissions scenarios upwards relative to those featured in the AR6, with at least some “overshoot” of the Paris Agreement’s “aspirational” target to limit global warming to 1.5C now “unavoidable”.
While modelling groups are just getting started on the full Earth-system model simulations, the emissions scenarios give a clear picture of the range of futures that will inform the IPCC’s seventh assessment cycle (AR7).
Here, Carbon Brief unpacks how the new scenarios were designed and how they differ from the SSPs published almost a decade ago.
The article also compares CO2 emissions and warming outcomes between the new scenarios and their predecessors, explores the range of future warming outcomes and examines why the high end of the scenario range has shifted markedly downward.
Finally, Carbon Brief examines the scale of carbon dioxide removal (CDR) built into the scenarios and new extensions of scenarios to 2150 and beyond.
Key highlights from Carbon Brief’s analysis of the new scenarios include:
The seven new scenarios give a range of global warming in 2100 from 1.6C to 3.3C above pre-industrial levels – markedly narrower than the 1.5C to 4.7C range in their SSP predecessors.
The top of the scenario range has fallen for the first time in four generations of climate modelling. The highest scenarios used in the three previous IPCC assessment cycles all produced around 4.6-4.9C of global warming in 2100, whereas CMIP7’s high scenario only reaches 3.3C and has around half the cumulative CO2 emissions.
The new “medium” scenario that is analogous to policies in place today reaches 2.9C in 2100, crossing 2C around 2050 and 3C around 2110, with a one-in-four chance of exceeding 4C by 2150.
The lowest scenarios have shifted modestly upwards, as a future that avoids any overshoot of 1.5C is no longer considered plausible. The very-low scenario peaks at around 1.8C mid-century before falling back close to 1.5C by 2100.
The updated socioeconomic assumptions underpinning the new scenarios describe a more crowded and less wealthy planet than the original SSPs, with the global human population now peaking at 10.1bn people around 2080 in the medium pathway and income per person in 2100 between 10% and 25% lower.
Every scenario that limits warming leans heavily on carbon dioxide removal, with cumulative removals by 2150 ranging from 655GtCO2 in the very-low scenario to 2,360GtCO2 in low-to-negative scenario.
To simulate how human activity could shape the climate of the future, climate modellers must estimate future levels of “radiative forcings” – the external drivers that cause global warming. These include atmospheric concentrations of greenhouse gases, air pollutants and land-use changes.
Given that no one knows how the future will unfold, modellers use a handful of scenarios that span a wide range of plausible outcomes.
The Scenario Model Intercomparison Project (ScenarioMIP) coordinates the development and running of emissions scenarios for climate models used in IPCC reports.
In April 2026, high-level details about the new set of scenarios for CMIP7 were published in the journal Geoscientific Model Development (GMD).
On 1 September, the underlying emissions data was released into the public domain by the ScenarioMIP team.
There are seven new CMIP7 scenarios designed to drive model simulations for AR7. The first model runs took place in spring 2026 and initial results are expected later this year.
The previous SSP scenarios were starting to show their age. Finalised in 2015-17 using historical data ending in 2015, several years projected by the SSP scenarios were already in the past by the time AR6 concluded in 2021. Meanwhile, the world had changed considerably.
(For a full guide to the SSPs, see Carbon Brief‘s 2018 explainer.)
Storylines and emissions levels
The most visible change in the new generation of scenarios is their names. Where the SSPs combined five socioeconomic “storylines” with radiative forcing targets (SSP1-2.6, SSP5-8.5, etc), the CMIP7 scenarios are named simply for the emissions trajectory that they follow.
The table below summarises the seven scenarios and the integrated assessment model (IAM) that produced each “marker” run – in other words, the specific IAM run used to generate the scenario that, in turn, will be used by CMIP7 climate models. IAMs run simulations of how the future energy system and emissions may evolve under different assumptions around socioeconomics, future technology costs and climate policy.
The table below also details how the scenario fares against a number of key metrics assessed by Carbon Brief, including CO2 emissions and warming outcomes.
(For more on Carbon Brief’s approach, see: Methodology.).
1.5C with higher overshoot, then net-negative greenhouse gases
-25
384
1.7 (1.2-2.5)
Warming values are medians (with the 5-95% range) from the 841-member FaIR ensemble used in this article (see: Methodology); the marker model assignments come from the ScenarioMIP database. Note that scenario names in the database differ from the official CMIP7 names (for example, the high-to-low scenario appears as “SSP5 – Medium-Low Emissions_a”).
Each of the new scenarios is built on a set of updated SSP storylines similar to those used in the original SSP scenarios. These include assumptions about future population, technological and economic growth, as well as potential for international cooperation that shape the resulting emissions pathways. The socioeconomic assumptions underlying these revised SSPs were updated in 2024 with new population and economic projections.
Most of the new emissions scenarios are now based on the “middle-of-the-road” SSP2 that assumes current socioeconomic trends broadly continue, with only one scenario using each of SSP1 (“sustainability”), SSP3 (“regional rivalry”) and SSP5 (“fossil-fuelled development”). None of the new scenarios uses SSP4 (“inequality”).
The solid lines in the figure below show updated global human population, GDP and GDP per capita values in CMIP7 (solid lines), compared to the original SSPs from CMIP’s sixth phase (CMIP6), shown by the dashed lines.
World population (left), GDP (centre) and GDP per capita (right) for SSPs 1-5 in the original 2013-era SSP database (dashed) and the 2024 update (solid). Note that the updated SSP1 and SSP5 population curves effectively overlap. GDP is shown in 2017 US dollars PPP, with the original converted from 2005 US dollars using the US GDP deflator (x1.235). Data from the IIASA SSP database; chart by Carbon Brief.
The change in socioeconomic assumptions is substantial. Global population was revised upward in nearly every scenario, with the updated SSP2 projecting there will be 9.9 billion people in 2100 – an increase of 1 billion people compared to the 2013-era SSP.
GDP was revised downward in the high-end growth scenarios (SSP1 and SSP5), slightly upward in SSP3 and SSP4 and was largely unchanged in SS2.
The combination of these changes means that income per person in 2100 is around 10-25% lower in most scenarios, with only SSP3 and SSP4 seeing mostly unchanged income per capita.
In short, the socioeconomic world underlying the new scenarios is somewhat more crowded and less wealthy per person than the one the SSPs originally imagined.
Another notable change is the shift in the SSP that underlies the highest future emissions scenario.
In the original SSPs, the “very high” SSP5-8.5 scenario was based on SSP5, while the new “high” scenario in CMIP7 is based on SSP3.
The GMD study explains that this is because IAM teams that developed the scenarios found that SSP3 and SSP5 variants produced similar emissions. They judged that the “fragmented” SSP3 world – which is characterised by large challenges to adaptation – to be more relevant for exploring high-end risks.
No more ‘baseline’ scenarios and other changes
In another important change, the authors of the CMIP7 scenarios decided to eliminate “baseline” scenarios that assumed a world without any climate policy. These scenarios were previously used as a counterfactual against which to compare climate-changed worlds.
Instead, the range of future emissions scenarios starts with current policies and explores ways that they could be strengthened, weakened, or kept the same. The high scenario explores a plausible “rollback of current mitigation policies“.
The medium scenario, by contrast, extends climate policies officially implemented as of 2025, without assuming countries achieve their Paris Agreement pledges – known as nationally determined contributions (NDCs) – or net-zero targets that are not yet backed by legislation.
In their GMD paper, the authors of the CMIP7 scenarios emphasise that the medium scenario “should not be considered as a ‘most likely’ scenario”, but that it can provide a benchmark against which the effect of future policy strengthening or weakening can be measured. It is roughly analogous in its emissions levels to the old SSP2-4.5 scenario.
The new low scenario explores a world where climate policy is rapidly strengthened and warming by 2100 is limited to below 2C. This makes it analogous to the old SSP1-2.6 scenario.
The very-low scenario limits global warming to around 1.5C by 2100, similar to the old SSP1-1.9 scenario. However, it involves a greater degree of overshoot mid-century, reflecting the fact that global emissions did not begin to rapidly decline in 2020 as envisioned by SSP1-1.9. As the authors of the GMD ScenarioMIP paper point out: “At this point of time, some overshoot of the 1.5C seems unavoidable.”
In addition, there are a number of scenarios that start on one path before undertaking rapid mitigation. These high-to-low, medium-to-low and low-to-negative scenarios are intended to explore futures where mitigation is further delayed, followed by a rapid turn-around later in the century.
The scenario developers noted that there is no specific likelihood or probabilities assigned to any scenario, but rather only a judgement that all are within the realm of plausibility given where the world is today. They also said that “there might be potential futures outside the ScenarioMIP scenario range”.
Timescales and other changes
In addition to the shift away from baseline scenarios, there are three other notable design changes made in CMIP7.
First, CMIP7 models will be driven by emissions of CO2 and other greenhouse gases, rather than set atmospheric concentrations.
In every previous generation of models, the ScenarioMIP experiments required that modelling groups simulate future climate using the same set of CO2 concentrations. For CMIP7, models with an interactive carbon cycle are asked to run in “emissions-driven” mode for CO2, calculating atmospheric concentrations themselves based on emissions.
This is a significant improvement. It means that the substantial uncertainty in carbon-cycle feedbacks will now show up directly in the range of projected warming, rather than being overlooked. (The change applies to CO2 only; methane, nitrous oxide and halocarbons remain prescribed as concentrations.)
Second, emissions match observations up to 2023. IAM modellers were asked to stay close to observed trends up to 2025 to avoid emissions diverging from reality before models were run. Scenario differences only open up after 2026, avoiding an earlier problem of scenarios diverging from reality years before the models were even run.
Finally, the period over which models are being run has been extended from 2100 to 2150. This is important as the world is already more than a quarter of the way through the 21st century.
The extended model runs out to 2150 will provide a more thorough exploration of the warming that people born in the coming decades may experience within their lifetimes.
In addition, all scenarios have extensions to 2500 where temperatures are eventually stabilised. These allow scientists to explore changes to long-term Earth-system processes, such as ice sheets and sea level, as well as whether warming is reversible.
A narrower range of future CO2 emissions
Overall, the new scenarios provide a notably more narrow range of future CO2 emissions than the SSP scenarios used in CMIP6.
The figure below shows net global CO2 emissions (combining fossil-fuel and land-use emissions) for the seven new scenarios, alongside the five SSP scenarios used for climate model runs in CMIP6 (e.g. SSP1-1.9, SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5).
Net global CO2 emissions (GtCO2/yr) in the seven CMIP7 scenarios (solid lines, coloured) and the CMIP6-era SSP scenarios (dashed) for the period from 1990 to 2100. CMIP7 scenarios are harmonised to 2023, while SSP scenarios (from RCMIP) were harmonised to 2015. Data from the ScenarioMIP database and RCMIP; chart by Carbon Brief.
At the bottom of the range, the new scenarios closely track their predecessors: the very-low scenario reaches net-zero CO2 around mid-century much like SSP1-1.9, while the low scenario lands close to SSP1-2.6.
The chart below shows total emissions for the same scenarios for the period 2024-2100.
Cumulative global CO2 emissions (GtCO2) between 2024 and 2100 in the seven CMIP7 scenarios (solid colours) and the CMIP6-era SSPs (light colours). Data from the ScenarioMIP database and RCMIP; chart by Carbon Brief.
The lowest emissions scenarios now have somewhat higher total emissions, reflecting the failure of the world to rapidly reduce emissions after 2020 that occurred in the lower SSP emissions scenarios, such as SSP1-1.9 and SSP1-2.6. The very-low scenario results in 310bn tonnes of CO2 (GtCO2) cumulative emissions between 2024 and 2100, compared to around 110GtCO2 in SSP1-1.9.
At the top end, the change is particularly dramatic. The high scenario in CMIP7 reaches 55GtCO2 per year in 2100. The previous high scenario, SSP5-8.5, by contrast, reached around 126GtCO2 per year in 2100.
In cumulative terms – which is what matters most for global warming – high reaches around 3,820GtCO2 over 2024-2100, half the roughly 7,600GtCO2 of SSP5-8.5 and about three-quarters of the 5,140GtCO2 of SSP3-7.0.
To put it another way: the top of the new scenario range sits between SSP2-4.5 and SSP3-7.0 in cumulative emissions terms, which is territory that CMIP6 treated as its middle ground.
To make the scale of this shift clear, Carbon Brief analysed the CO2 emissions trajectories in each of the prior generations of high-end emissions scenarios, using the same simple climate model – FaIR – to calculate future warming.
Fossil CO2 emissions relative to 1850-1900 for the highest scenario of each climate modelling generation: SRES A1FI (CMIP3, used in AR4), RCP8.5 (CMIP5, AR5), SSP5-8.5 (CMIP6, AR6) and CMIP7’s high, all run through AR6-calibrated FaIR ensemble. Data: SRES database v1.1, RCMIP v5.1, ScenarioMIP database; chart by Carbon Brief.
Below, four different generations of emissions scenarios are examined. The SRES scenarios were originally published in 2000 and used in the IPCC’s third (2001) and fourth (2007) assessment reports (and the corresponding CMIP3 model runs). The RCPs were developed in the early 2010s and used in the IPCC fifth assessment report (AR5; 2013) and CMIP5, while the SSPs were developed in the late 2010s and used in the IPCC AR6 report and CMIP6.
Over the past two decades, the highest emissions scenarios all resulted in comparable amounts of warming in 2100: SRES A1FI (the highest SRES scenario) reached 4.6C in 2100 (5-95% range; 3.5-6.1C), RCP8.5 reached 4.9C (3.7-6.5C) and SSP5-8.5 reached 4.6C (3.5-6.2C).
(RCP8.5 edges out its successor despite lower CO2 emissions because it assumed considerably more methane and nitrous oxide.)
Global mean surface temperature change in 2100 relative to 1850-1900 (medians and 5-95% ranges) for the highest scenario of each climate modelling generation: SRES A1FI (CMIP3, used in AR4), RCP8.5 (CMIP5, AR5), SSP5-8.5 (CMIP6, AR6) and CMIP7’s high, all run through AR6-calibrated FaIR ensemble. Data: SRES database v1.1, RCMIP v5.1, ScenarioMIP database; chart by Carbon Brief.
CMIP7’s high scenario comes in remarkably lower, at 3.3C (2.6-4.4C).
The downward revision of future emissions in CMIP7 reflects two key changes since RCP8.5 was published back in 2011. First, the plausible baseline of a repeal of current policy has fallen. Cheap solar, wind and batteries, a global plateau in coal use and more than $2tr per year in clean-energy investment mean that a rollback in climate policy would not result in coal deployment levels assumed in the RCP8.5 scenario.
The GMD study states that CMIP6’s high-emission levels “have become implausible, based on trends in the costs of renewables, the emergence of climate policy and recent emission trends”.
(For more, see Carbon Brief’s recent factcheck of false claims around the retirement of the SSP5-8.5 emissions scenario. Also see Carbon Brief’s recent interview with Prof Detlef van Vuuren, a key architect of both the old SSPs and new scenarios.)
Second, part of the apparent decline reflects a correction of how scenarios are communicated – rather than real-world progress. The old high-end scenarios always represented an estimate of worst-case scenarios at the time, rather than likely outcomes.
Genuine progress in reducing emissions probably accounts for around 0.7C of the roughly 1.7C gap between SSP5-8.5 and today’s current-policy trajectory, with the remainder reflecting that the baseline was never particularly likely.
What the new scenarios mean for future warming
To compare warming outcomes across scenario generations on a like-for-like basis, Carbon Brief ran both the seven CMIP7 scenarios and the CMIP6 SSP emission scenarios through the same simple climate model.
These values may differ from the ultimate results that are found by CMIP7 climate models, but give a sneak peak of what those results may look like when they become available.
Median warming relative to 1850-1900 for the seven CMIP7 scenarios, with observations to 2025 (black) and the 5-95% ensemble range shaded for the medium and low scenarios. Dashed lines show warming between 2100 and 2150. Chart by Carbon Brief.
The seven scenarios produce warming in 2100, relative to pre-industrial (1850-1900), that ranges from 1.6C (with a 5-95% range of 1.1-2.5C) in the very-low scenario to 3.3C (2.6-4.4C) in high, with the current-policy medium scenario reaching 2.9C (2.2-3.9C). Warming also continues after 2100 in both the medium and high scenarios.
The figure below shows the range of 2100 warming (5th to 95th percentile) relative to the preindustrial period expected in each of the old SSP scenarios and the new CMIP7 ones, along with a central estimate (white dots).
Warming in 2100 for CMIP7 scenarios and CMIP6 SSPs run through the identical FaIR ensemble (medians and 5-95% ranges). Chart by Carbon Brief.
The largest changes are, unsurprisingly, at the top. CMIP7’s high scenario (3.3C in 2100) produces less warming than SSP3-7.0 (3.7C in the same ensemble) and far less than SSP5-8.5 (4.7C).
The entire CMIP6 “high” tier (e.g. SSP5-8.5 and SSP3-7.0) now sits above anything in the new scenario set, at least up to 2100. Extended beyond 2100, however, high keeps climbing towards levels the previous extreme scenarios reached earlier.
At the low end, the picture is more similar. The very-low scenario (1.6C in 2100) lands close to SSP1-1.9 (1.5C) and low (1.8C) is essentially indistinguishable from SSP1-2.6 (1.8C) in 2100.
However, the new low scenario involves more rapid late-century emissions reductions and greater amounts of carbon removal than its SSP analogue, while the very-low scenario involves greater overshoot of 1.5C mid-century.
Crossing warming thresholds
In addition to calculating 2100 and 2150 warming, Carbon Brief has calculated the likelihood of passing different global warming levels (2C, 2.5C, 3C, 4C and 5C) over time in the new CMIP7 scenarios.
The chart below uses the IPCC approach of calculating the crossing year based on a 20-year average, rather than when a single year exceeds the warming level.
Share of the 841-member FaIR climate model runs that exceed each warming level by year under the medium (top) and high (bottom) scenarios. Marked years show the median IPCC-convention (20-year average) crossing; percentages show the chance of exceeding each level by 2150. Chart by Carbon Brief.
Under the medium scenario, which reflects a world where current policies are maintained, passing 1.5C is essentially locked in.
Most models cross the threshold by the late 2020s or early 2030s. The 2C limit is crossed around 2050 on average and 3C by around 2110. The chance of exceeding 4C is around one-in-four by 2150, but, ultimately, rises to roughly 50% if emissions continue after that point.
Under the high scenario, 2C arrives in the 2040s, 3C in the 2080s and the chance of exceeding 4C by 2150 is around 60% (and around 95% by 2300). Even 5C is reached by 2150 in roughly 20% of climate model simulations.
The lower scenarios tell a different story. In the very-low scenario, the chance that peak warming (which the IPCC determines using a 20-year average of warming) ever exceeds 1.5C is around 90%. This reflects the fact that passing 1.5C is almost unavoidable at this point.
However, the chance of surpassing 2C sits at around 30% and the scenario has warming falling after mid-century as more CO2 is removed from the atmosphere than is added.
Carbon dioxide removal
Every scenario that has global warming peaking and declining requires pulling CO2 back out of the atmosphere. Otherwise, warming from CO2 emissions will persist for millennia.
CO2 removal (CDR) remains one of the few levers available to reduce future temperatures – particularly given additional warming caused by cuts to aerosol pollution.
The chart below shows the total CDR deployment in each of the different scenarios by year, reflecting the sum of both land-based and engineered approaches (top), as well as the total CDR deployment between 2024 and 2150 (bottom).
Total carbon dioxide removal (CDR) in the CMIP7 scenarios (solid) and their extensions (dashed), including both “engineered” and “novel” methods (bioenergy and carbon capture and storage (BECCS), direct air capture (DAC), enhanced weathering, biochar) plus land-based removals (the net land-use sink plus soil carbon management), along with with cumulative CDR for 2024-2150. Chart by Carbon Brief.
Every scenario that deeply cuts global emissions in CMIP7 also involves a large amount of CDR.
The low-to-negative scenario pulls a cumulative 2,360GtCO2 out of the atmosphere by 2150, roughly 60 years of today’s emissions run in reverse.
The high-to-low scenario has around 1,480GtCO2 cumulative CDR, medium-low has 1,450GtCO2 and low has 1,360GtCO2.
Even the very-low scenario, which seeks to minimise CDR use, requires 655GtCO2 of removals between 2024 and 2150.
In the low scenario, roughly one-third of the removals is from the land “sink”, while low-to-negative relies almost entirely on engineered methods, with direct air capture alone reaching around 16GtCO2 per year by 2100.
The chart below shows the deployment of engineered removals by year (top), as well as the total engineered CDR used between 2024 and 2150 (bottom). The lower plot also includes a breakdown between the portion of CDR that requires geologic storage (e.g. DAC and BECCS) and the portion that does not (e.g. enhanced weathering and biochar) and compares the total to a recent “prudent” total CO2 storage limit published in the scientific literature.
(For more on limits to carbon storage capacity, see Carbon Brief’s 2025 guest post.)
Engineered and novel CO2 removal only, with the cumulative BECCS and direct air capture component – the technologies requiring geological storage – compared against the “prudent” 1,460GtCO2 (range 1,290-2,710GtCO2) geologic storage limit set out in Gidden et al. (2025). Chart by Carbon Brief.
The amount of CDR going toward geological storage is most highest in the low-to-negative scenario, which injects around 1,750GtCO2 of BECCS and direct-air-capture CO2 underground by 2150.
The high-to-low and low scenarios each commit around 800GtCO2 to storage by 2150. This is within the range of available geologic storage, but would require that the storage industry handles more CO2 than the mass of oil currently moved by the fossil-fuel industry.
That said, there are other potential CDR approaches – such as enhanced rock weathering, surficial mineralisation and ocean alkalinity enhancement – that do not require injection of CO2 into geologic formations. In-situ mineralisation approaches that inject CO2 into alkaline rock formations such as basalt or peridotite could also open up more potential CO2 storage.
It is worth noting that the amount of CDR deployed in these scenarios would require planetary-scale engineering at the cost of trillions of dollars, while many of the engineered CDR approaches are still relatively early-stage technologies.
No single climate future
The goal of scenarios is to span a range of possible futures. While it may be tempting to treat current climate and energy policies – and the medium scenario – as a forecast, there is no reason to expect that they will not change in the future.
It is likely that policies will continue to be strengthened, as has been the case over the past two decades. However, they may also be weakened if national priorities or politics change, as has happened in the US during the two terms of the Trump administration.
In the new CMIP7 scenarios there is no “business-as-usual” scenario, but rather a narrower range of futures than was available in CMIP6, reflecting greater clarity among scientists on where the world is heading in terms of future energy use and emissions.
The fact that the worst-case scenarios of the past have become increasingly implausible is good news. However, this is tempered by the fact that the very-low emission scenarios have, in turn, become harder to achieve given that global emissions have yet to decline.
There is also real uncertainty in the climate-system response to emissions. This is due to uncertainty around how sensitive the climate is to a build-up of CO2 in the atmosphere, as well as how the carbon cycle will respond to emissions.
The CMIP7 medium scenario – which has a central estimate of 2.9C of warming by 2100 – still has around a 3% chance of reaching 4C by that date. If emissions continue, those odds increase to 25% by 2150. This remains far outside anything resembling a safe outcome for the climate system.
The scenarios are now being run using the new CMIP7 models, whose emissions-driven runs will fold carbon-cycle uncertainty directly into projections. These projections will subsequently be analysed in the reports of AR7.
Ultimately, it will be decisions made by governments, businesses and individuals that decide which of these seven futures become closest to reality.
Methodology
Emissions scenarios shown in this article are the seven CMIP7 ScenarioMIP scenarios set out in van Vuuren et al. (2026), harmonised to observed 2023 emissions, with rule-based extensions to 2500 generated using the FLEX methodology. Emissions through 2100 match the ScenarioMIP database; extension trajectories are indicative and may differ from the final published extensions.
Temperature projections use FaIR v2.2 with the fair-calibrate v1.4.5 constrained ensemble (841 members set out in Smith et al. (2024), which matches the AR6 assessed climate sensitivity (ensemble ECS median 3C, 5-95% 2.0-5.1C), historical warming and ocean heat content.
Historical emissions (1750-2022) use the FaIR historical emissions dataset, with scenario emissions spliced in after 2023.
Solar and volcanic forcing are updated through 2025 from the Climate Indicator forcing timeseries; future volcanic forcing ramps to the 1850-2021 climatological background by 2035 (following the CMIP7 protocol) and solar forcing follows a SOLARIS-HEPPA-derived cycle projection to 2300.
All warming is expressed relative to 1850-1900.
SSP comparisons run the RCMIP-harmonised CMIP6 scenario emissions through the FaIR ensemble, which yields 2081-2100 warming 0.1-0.3C below the AR6-assessed values at the high end (e.g. SSP5-8.5: 4.2C vs 4.4C assessed), reflecting differences between the AR6 assessment and the FaIR configurations used here. Updating the volcanic dataset to use CMIP7 values (which revises the eruption-rich 1850-1900 baseline period) raises all reported anomalies by 0.03-0.05C.
For CDR, the scenario database reports the technology split (for example, BECCS, direct air capture, enhanced weathering, biochar, ocean-based, soil carbon management). Agriculture, forestry and other land-use (AFOLU) removals are available only as a net flux, so are shown as the net sink where negative. Soil-carbon management is grouped with land-based rather than engineered removal, and the geological storage comparison uses BECCS plus direct air capture only.
The figure showing high-end scenarios for the past four CMIP generations runs SRES A1FI through the same ensemble using the A1G MiniCAM model from the SRES database v1.1, spliced onto historical emissions at 2000, and covering CO2 (fossil and land use), methane, nitrous oxide and sulphur; SRES-era ozone-precursor projections (nitrous oxide, carbon monoxide and volatile organic compounds) lie outside the calibrated range of FaIR, so RCP8.5 values are used instead. RCP8.5 uses RCMIP v5.1 emissions, with 13 minor halogenated gases absent from the RCP database following SSP5-8.5.
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When Rojo Neog’s village in northeast India was hit by a power cut in July, he headed out to buy candles. Three days later, his body was recovered – swept away by surging floodwaters. His niece said the water had risen from knee- to neck-level in about half an hour.
The devastating floodshighlight how climate risk across India is becoming harder to confine to a season or a disaster bulletin. Just weeks before the disaster in Assam, authorities in Mumbai rationed water as reservoir storage fell to just over 10%.
India does not lack warnings about climate risk. The more difficult task is making sure money, institutions and communities are ready to act before those warnings become disasters. Adaptation should not be just an obligation once a crisis has arrived, but an investment made while there is still something to protect.
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As governments head towards COP31 in Antalya this November, India should push not only for more adaptation finance, but for finance that arrives earlier and can be traced to outcomes on the ground.
That is the gap India needs to close if we wish to become truly resilient in the face of the changing climate. Money must move with risk, institutions must know what to do before an emergency is declared, and long-term spending must reduce vulnerability before it becomes loss.
India’s adaptation disconnect
This year the disconnect has become painfully clear in Assam, where more than 100 people have died due to the flooding, with nearly 140,000 people across seven districts affected. More than 450 villages remain inundated, while some 49,000 people are taking shelter in relief camps after losing everything.
No financing mechanism can stop a river from rising. But timely measures can change what happens before it does. If forecasts and river levels triggered financing before the water arrived, authorities could position boats and stock shelters, and evacuate people where needed, while families could move cattle, seed, medicines and documents before roads disappeared.
India already has much of the information needed to address climate change. High-risk states and districts should agree in advance which local thresholds trigger action, who is responsible and how funds will be released, so officials do not have to negotiate responsibility and budgets from scratch once risk becomes an emergency.
Linking community know-how to financing
Our work in Majuli, a river island district in Assam, shows why this matters.
Across 64 villages, communities helped identify flood and erosion risks, assess their capacity to respond, and to develop resilience measures with indicative budgets and possible funding sources.
Communities often know what would help; the harder task is connecting that knowledge to institutions and finance that can act on it.
Public health offers an example of how systems can adapt as risks change. In New Delhi, vector-control workers who once prepared for a defined “dengue season” now remain on alert throughout the year, using surveillance and hotspot mapping to identify risks earlier.
The next step is to make these systems more predictive by integrating climate forecasts into public health planning.
India needs sustained investment in drainage, health systems, wetlands, water security and climate-resilient agriculture. Some will remain public responsibilities; others, including water reuse, efficient irrigation, resilient cold chains and risk-proofed infrastructure, can generate savings or revenue and attract private capital if projects are prepared well.
The economic case for adaptation is not always about generating new revenue. Often, it is about avoiding future costs. Flood shelters, public-health preparedness, early-warning systems and support for the poorest households will still need public or grant finance. The point is to match the finance to the risk rather than treat adaptation as a single financing problem.
A sugarcane farmer removes weeds which have grown in floodwater in Kolhapur district, Maharashtra, India. Credit: Meenal Upreti
A sugarcane farmer removes weeds which have grown in floodwater in Kolhapur district, Maharashtra, India. Credit: Meenal Upreti
Rising disaster bill shows cost of inaction
India is already spending heavily on adaptation, with related expenditure reaching 5.6% of GDP in 2021-22. Yet tracked adaptation finance was only about $15 billion annually, almost entirely from domestic public sources, against estimated needs of about $100 billion a year through 2030.
Internationally, the shortfall is wider: developing countries may need $310 billion-$365 billion annually by 2035, compared with just $26 billion in international public adaptation finance in 2023.
For governments repeatedly paying for flood, droughts and heat relief, the cost of inaction can quickly exceed the cost of building resilience, though not all the costs of inaction appear neatly on a balance sheet.
In floodplain landscapes such as Assam’s Kaziranga National Park, animals move towards higher ground every monsoon as the floodplain fills, crossing roads and leaving the park in search of safety. During the 2024 floods, 215 animals died, including 13 one-horned rhinos.
Development plans in such sensitive landscapes must leave room for water, wildlife and communities to move safely. A wetland may not generate monetary revenue, but the floodwater it stores has real value. The cost of losing that capacity may only become visible when the next flood arrives.
Success should not be measured only by how quickly relief follows a disaster. It should also be measured by what never had to be replaced: people and animals moved before the water rose, seeds kept dry, medicines waiting at the shelter, a wetland that still had room to hold water, and a family that could leave while the road was still open.
Adaptation becomes an investment when it preserves those choices before they disappear.
