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Research on climate change in urban areas is skewed towards large, well-established cities in the global north, according to analysis of more than 50,000 studies.

The research, published in Nature Cities, uses keyword searching and machine-learning methods to produce a database of studies on climate change and cities published over 1990-2022.

The authors find that small, fast-growing cities – especially in Africa and Asia – are underrepresented in their database.

“While cities like London, New York and Berlin are extensively studied, fast-growing cities such as Goma (Democratic Republic of the Congo), Surat (India) and Huế (Vietnam) are barely visible in the literature,” one study author tells Carbon Brief.

Inhabitants of these cities have collectively contributed very little to global greenhouse gas emissions, but face the greatest impacts from the warming planet, the authors say.

The paper finds that literature on climate change and cities is growing “exponentially”, with 84% of studies on this topic published over 2012-22.

The new analysis is published as scientists from around the world start work on the Intergovernmental Panel on Climate Change (IPCC) special report on climate change and cities, which is due for publication in March 2027.

The study finds that, in its most recent set of headline reports, the IPCC captured “only” 5% of the total available literature on climate change and cities.

One study author tells Carbon Brief that the study is a “call to action” for the IPCC and broader research community “to synthesise more, to look beyond familiar places and to take seriously the diversity of urban realities that will define the future of climate mitigation and adaptation”.

Climate change and cities

More than half of the world’s population live in cities. These densely populated areas are responsible for the majority of global emissions and are also hotspots for climate extremes, including heatwaves and flooding.

Research about climate change and cities is a fast-growing field that encompasses, among other topics, the impacts of climate change on city infrastructure, adaptation measures that city-dwellers are taking and technological measures to limit emissions from cities.

The IPCC’s upcoming assessment report will feature its biggest overview of research on cities to date, as the organisation has commissioned a special report on climate change and cities as part of its upcoming assessment cycle. The report’s outline has already been agreed and the final document is scheduled for publication in March 2027.

However, the new study argues that, without a dedicated effort to “pre-aggregate the underlying literature by the entire research community”, the IPCC “may struggle to deliver a balanced and comprehensive review”.

The new analysis is the “first global stocktake of literature” on climate change and cities, according to a press release from the University of Sussex. The research was produced in-part to help advise the authors of the IPCC report about the current landscape of literature on climate change and cities, the study authors tell Carbon Brief.

Author Dr Tim Repke is a researcher at the Potsdam Institute for Climate Impact Research. He tells Carbon Brief that he hopes that the new study “can serve as a starting point of searchable, clean data” to help the authors of the upcoming IPCC special report to “do their work more efficiently”.

A growing field

The amount of literature on climate change in cities is “much larger than previously estimated”, the paper says.

Moreover, the analysis points to “rapid, exponential growth” in literature on climate change and cities over the past three decades.

The graph below shows the number of studies about climate change and cities published each year over 1990-2022 (dark blue) and the subset of studies that focus on specific city case studies (light blue).

The plot also shows how many studies were published during the writing periods of each IPCC assessment report. For example, 37,539 studies on climate change and cities were published in time to feature in the IPCC’s sixth assessment cycle (AR6).

The number of studies published each year over 1990-2022 that focus on climate change and urban areas
The number of studies published each year over 1990-2022 that focus on climate change and urban areas (dark blue) and specific city case studies (light blue). Source: Montfort et al (2025).

The authors find that 84% of studies in their database were published over 2012-22.

Literature on climate change and cities is currently growing 4.5 times faster than literature on climate change alone, they add.

Dr Simon Montfort is a postdoctoral researcher at Switzerland’s École Polytechnique Fédérale de Lausanne and lead author of the study. He tells Carbon Brief that the rapid growth in literature on climate change and cities is “not really surprising” because population growth in cities means that these areas are “becoming more and more important”.

The data can be explored further in their interactive online tool.

Uneven focus

There is a well-established skew in climate change literature towards wealthy nations in the global north. The new study finds that this skew is highly evident in literature on climate change and cities. 

The map below shows the locations of the 20,000 “case study” papers. Darker colours indicate more highly researched areas. The map shows cities that were researched in one study (pink), between one and five studies (orange) and in more than five studies (red). The graph in the bottom left shows this information broken down by continent.

The number of cities that are not researched at all, or only covered in one study
The number of cities that are not researched at all, or only covered in one study (pink), between one and five studies (orange) and in more than five studies (red). Source: Montford et al (2025).

The authors identify more than 4,000 studies in Europe and 3,000 in North America. According to the authors, half of cities in these continents are covered by more than one study.

However, the map reveals a lack of research focused on cities in central and South America, Africa, the Middle East and south and south-east Asia.

The authors identify more than 8,900 studies focused on cities in Asia. One-third of these focus on Chinese cities, they find. The authors identify more than 1,500 studies on Beijing alone, most of which focus on mitigation, rather than impacts or adaptation.

Meanwhile, they find that 92% of cities in Africa are researched in no more than one study. Nigeria is the most highly studied country on the continent, with almost 400 studies – half of which focus on Lagos.

The authors identify a bias in their research database towards large cities with high emissions. Meanwhile, they find that small, fast-growing, non-coastal cities are underrepresented in the literature.

Prof Felix Creuztig is the head of the working group on cities at the Potsdam Institute for Climate Impact Research. He is an author on the study and on the upcoming IPCC special report. 

He tells Carbon Brief:

“While cities like London, New York and Berlin are extensively studied, fast-growing cities such as Goma, Surat and Huế are barely visible in the literature. These smaller and rapidly urbanising cities in Africa and Asia are precisely where climate risks and emissions are increasing fastest, yet they are strikingly underrepresented.”

50,000 studies

To identify all existing literature on climate change and cities, the authors conducted their search using the open-access research database OpenAlex.

They first used a long list of keywords to search the abstracts of every paper on OpenAlex for research focused on cities and climate change. Keywords for literature on cities included “urban” and “built-up”, while key words for climate change ranged from “changing climate” to “carbon taxes”.

They then checked these papers using a “machine learning classifier”, which filtered out any research that was unsuitable.

The authors used a machine-learning approach to scan the abstracts of studies in their database, to determine which topics are most frequently covered.

More than half of the papers in the database were focused on mitigation, the authors found. The impacts of climate change on cities was covered in around 15,000 papers, and the rest covered adaptation and “cross-cutting” topics.

Lead author Montfort tells Carbon Brief that the database of 50,000 articles is “quite a precise sample, meaning that it includes few irrelevant articles”.

However, he adds that there may be “many relevant articles missing from our sample”. For example, the authors find that their database does not completely capture literature from the “physical sciences”, such as smart energy grids or radiative cooling methods.

Language is another notable bias, as the database only includes research published in English.

Dr Doan Quang Van is a researcher at Japan’s University of Tsukuba and a lead author on the upcoming special report. He praises the study, but notes that the English-only database likely leads to an “underappreciation of non-English regions”.

He also notes that Indigenous knowledge, which is “not necessarily contained in ‘official documents’ like papers or reports” is not included in the database.

IPCC recommendations

The authors compare the tens of thousands of studies cited by the IPCC in its most recent assessment cycle – AR6 – to their own database of literature on cities and climate change. They estimate that the IPCC cited almost 2,500 studies from the database in AR6, representing around 5% of the total.

They find that the IPCC’s choices about which studies to include further deepens the skew towards “large and mega cities” in the global north that is already evident in the literature.

Lead author Montfort tells Carbon Brief that the case studies are a “rich-evidence base” of “nuanced, case-specific knowledge”.

He says that it is important to expand the evidence base to less well-studied cities, but acknowledges it is “highly infeasible to conduct a study for every single city”. As such, he suggests that researchers should “look for ways to generalise findings from the more than 20,000 city-specific case studies already available”. He adds:

“If cities can learn from each other’s experiences, the existing evidence could go much further in informing city practitioners.”

To do this, the authors suggest that scientists should develop a data-driven method of grouping cities based on size, location and language, to enable “cross-city transfer learning from successful climate solutions”.

Dr Tamara Janes is a member of the climate information for international development team at the UK Met Office and an author on the upcoming IPCC special report. She was not involved in the new research.

She tells Carbon Brief that the study is “useful and timely”, adding that it “will undoubtedly help the ongoing special report by providing a solid foundational understanding for the current state of urban research worldwide”.

Janes adds that “this type of study is not only useful for researchers to design their research questions, but also for donor agencies as gaps in research can then be prioritised through flexible funding initiatives”.

Study author Crueztig says:

“For the IPCC and the broader research community, this is a call to action: to synthesise more, to look beyond familiar places and to take seriously the diversity of urban realities that will define the future of climate mitigation and adaptation.”

IPCC working group two co-chair, Dr Winston Chow, tells Carbon Brief that the “voluminous literature on climate change today presents challenges in its assessment”. He adds:

“Our experts are aware of these challenges towards developing reliable findings in informing our assessments and the IPCC is formally discussing this issue in a forthcoming expert workshop on methods of assessment.”

The authors add that they hope their interactive map, which is available online, will update automatically in the future to provide a “searchable, interactive, living database” of literature on climate change and cities. 

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Fast-growing, global-south cities are ‘strikingly underrepresented’ in climate research

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Climate Change

Pawa in Palau

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This week our powerful Pacific team is in Palau for the Pacific Islands Forum Leaders Meeting. This is a major moment in our campaigns for Pacific climate justice and to stop deep sea mining. So what’s it all about, what can we expect over the coming days, and why is this year’s meeting in particular so important? Read on to find out!

*Pawa is Melanesian word meaning collective power.

Meet Moemoana Schwenke, our Pacific Climate Campaigner

“When you love something deeply, you do everything you can to protect it.”

@greenpeaceap

For us in the Pacific, protecting our home is an expression of love. Follow our journey across the Pacific all the way to COP31 in Türkiye. Pacific voices continue to lead the call for climate justice champion our priorities and build a movement for a Fossil Fuel Free Pacific, from our islands to the world. Join the movement and follow the journey. @Moemoana Schwenke

♬ original sound – Greenpeace Australia Pacific

What is the Pacific Islands Forum (PIF)?

The Pacific Islands Forum, or ‘PIF’, is our region’s most important political organisation. It is where countries of the Pacific — including Australia and New Zealand — come together to collaborate on shared challenges and to set collective goals.

The PIF Leaders Meeting is an annual weeklong event that includes a dedicated meeting of the Pacific’s small island developing states (PSIDS), many special side events organised by Pacific civil society, the leaders’ meeting itself, and more. At the end of the week, leaders issue a Forum Communiqué, capturing what they have agreed on, their shared priorities and the actions they will take together.

This year’s meeting is being held in the beautiful northern Pacific nation of Palau, the same place our Pacific team gathered back in January to plan for the year.

Islands in Palau
© Hector John Periquin

What’s at stake this year?

Climate change has dominated the PIF for decades. Pacific leaders have been crystal clear it is their number one priority, and the annual gathering is the moment they can exert maximum pressure on Australia over its fossil fuel record.

The voyage to COP31

This year’s meeting comes less than three months before COP31, where Australia will take on the role of President of Negotiations — a role it has committed to undertaking in partnership with the Pacific — and less than a month before the ‘Pacific Pre-COP’, to be held in Fiji and Tuvalu.

Following a fraught round of mid-year negotiations in Bonn, PIF leaders will need to set out a clear vision and priorities for COP31. These include accelerating a just global transition away from fossil fuels, defending science as the foundation of international climate cooperation, and increasing the availability and accessibility of finance for renewable energy and climate adaptation.

Pictured left to right - 
- Dr Simon Bradshaw, COP31 Lead and report author, Greenpeace Australia Pacific
-Belyndar Rikimani, Campaigns and Research Lead, Pacific Islands Students Fighting Climate Change
-Shiva Gounden, Head of Pacific, Greenpeace Australia Pacific
© Greenpeace / Marie Jacquemin

Accountability for Australian fossil fuel exports

Since the last PIF Leaders Meeting, Australia has signed the Belém Declaration on the Transition Away from Fossil Fuels. The declaration reaffirmed the legally binding commitment to help limit global warming to 1.5°C and recognised that this is incompatible with new fossil fuel production. Yet, Australia has continued to approve new coal and gas projects, including at least five since the last PIF Leaders Meeting.

Barry Dick observes the community graveyard impacted by coastal erosion on Pele Island in Vanuatu.
© Niki Kuautonga / Greenpeace

What is Greenpeace doing?

We’re going big this year, taking six members of our team to Palau to support Pacific leaders to hold the line, hold Australia accountable, and show the world what’s at stake. We’ll lobby leaders, hold press conferences, share our messages with the world, and support our incredible local partners in Palau.

Members of the Greenpeace Pacific team at the Pacific Islands Forum leaders' meeting in Palau, 2026.

How can you get involved?

PIF is the first in a drumbeat of major moments where we’ll be carrying the voices of the Pacific to the world. Come October we’ll be voyaging to Fiji on our ship Oceania for the Pacific Pre-COP, and in November we’ll be off to Antalya for the world’s climate negotiations (COP31).

Learn more about the Pacific way to a fossil fuel free future by checking out our report and exhibition.

Follow our journey, and check back here for more ways to join the movement for climate justice. Together we have the pawa!

Pawa in Palau

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Climate Change

From firefighting to future-proofing: Preventing wildfires must be the priority

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Gill Einhorn is head of the Forest Future Alliance and Natalie Çilem is community lead of the Global Wildfire Leadership Network.

Wildfires have devastated communities across the world this summer, claiming lives, displacing thousands of people and leaving billions in economic damage in their wake. In Europe alone, wildfires have already caused an estimated €19 billion in losses this year.

They are an economic, financial and public health challenge that is growing faster than many governments and markets are prepared for – and exposing the real costs of poor land management.

A system built for recovery, not resilience

Far more money is currently spent responding to the disastrous effects of wildfires than preventing them in the first place. The United Nations Environment Programme estimates that more than half of wildfire-related spending goes towards response, while planning receives only around 0.2 percent. This problem is not limited to wildfires; over 95 percent of disaster aid between 2005 and 2017 was allocated to response, and less than 4 percent was directed towards prevention or preparedness.

Forests are critical, but without investment in how land is managed and protected, their value is neither stable nor guaranteed. Protecting forests requires investing not only in conservation, but in the conditions that keep forests standing.

    Each dollar invested in wildfire-resistant construction could save around $210 in avoided future economic losses, according to a report by the World Economic Forum and Forest Future Alliance. Despite this evidence that prevention can significantly reduce future costs, wildfire resilience remains chronically underfunded.

    This spending discrepancy is creating significant challenges for insurers, asset owners and financial institutions. Global insured losses from natural catastrophes reached $107 billion in 2025, with wildfires, floods and storms accounting for 92 percent of claims.

    In this context, insurers are reassessing where and how they are willing to underwrite risk. Around 56 percent of global wildfire losses between 2000 and 2023 were uninsured. In some high-risk areas, insurers are scaling back coverage altogether, leaving homeowners, businesses and governments to shoulder a growing share of the costs – making it increasingly difficult to break even.

    Proven solutions are already paying off

    In many regions, wildfires are driven not by natural causes but by the deliberate clearing of land for agriculture. Degraded landscapes are becoming drier, more flammable and increasingly vulnerable to catastrophic loss, creating a vicious cycle of deforestation, economic damage and rising emissions.

    The answer is not simply stronger firefighting capacity. Governments, investors and businesses must work together to shift capital upstream into prevention, resilience and long-term landscape stewardship of healthy forests. That means planting appropriately, investing in heat-resistant species, exploring approaches that minimise fire footprints through active management, and exploring the AI and technology solutions that are burgeoning.

    A burnt olive tree in an area affected by a wildfire in Ano Sichaina near Patras, Greece, August 14, 2025. REUTERS/Louiza Vradi

    A burnt olive tree in an area affected by a wildfire in Ano Sichaina near Patras, Greece, August 14, 2025. REUTERS/Louiza Vradi

    Solutions to this already exist and are proven to have an impact. Following devastating wildfires year-on-year, Portugal shifted its approach to wildfire management, increasing prevention spending within its national rural fire management system from around 20 percent in 2017 to approximately 60 percent in 2022. While many countries remain locked in a reactive cycle of disaster response, public policy can shift investment upstream and make resilience a priority before fires occur.

    Indigenous communities have long used proactive land stewardship to reduce wildfire risk while supporting healthy and productive landscapes. For example, the Cheslatta Carrier Nation in British Columbia traditionally managed fuels through cultural fire practices but now implements mechanised fuel removal methods under commercial agreements. By combining Indigenous stewardship with sustainable forest management, Cheslatta is generating community benefits while also boosting wildfire prevention.

    Resilience can also be strengthened through finance and technology. FireSat, a partnership led by Earth Fire Alliance with Google.org, the Gordon and Betty Moore Foundation and Muon, is a satellite constellation designed for rapid wildfire detection. Scanning every 20 minutes, it can detect fires 400 times smaller than current systems and track them through smoke and darkness in almost real time. In California alone, FireSat could prevent up to 350,000 acres from burning each year. It has recently received significant new investments allowing it to expand towards a constellation of more than 50 satellites that will monitor every point on Earth every 20 minutes or less.

    In Brazil’s Pantanal, the Embrace the Forest initiative uses AI-powered detection towers across 2.5 million hectares to support earlier intervention and faster response. During the severe 2024 fire season, the initiative contributed to a 40 percent reduction in burned area compared to 2020.

    A drone view shows burnt cars following a wildfire in Dymi, near Patras, Greece August 14, 2025. REUTERS/Louiza Vradi

    A drone view shows burnt cars following a wildfire in Dymi, near Patras, Greece August 14, 2025. REUTERS/Louiza Vradi

    These examples illustrate what is possible when resilience is treated as an investment priority rather than a recovery cost. But we must ensure funding for these measures is scaled before disaster strikes. Initiatives like the Global Wildfire Leadership Network (GWLN) are key, bringing together corporate decision-makers, investors, insurers, governments and Indigenous leaders to direct investment towards prevention and align finance, technology and stewardship to protect nature, safeguard communities and strengthen future economic stability. With a goal of doing more together than the sum of our parts, the network focuses on Forest Future Alliance GWLN Solutions Labs – where partners sign up with the intent to collaborate.

    Rewarding prevention

    Financial incentives must be created that reward prevention. This can be done by scaling public-private partnerships, supporting long-term landscape stewardship, investing in community capacity including Indigenous wisdom and technology. Ultimately, our terrestrial natural reserves are critical infrastructure that support resilient economies and thriving communities.

    One in three people are dependent on forest services, goods and economic opportunities for survival, so it’s in all our interests to protect what we have. Forests support cooling, water and food security – and are a very cost-effective way of removing carbon dioxide from the atmosphere, where done appropriately.

    UN chief warns climate crisis “in overdrive” as El Niño threatens to fuel the fire

    No sector can solve this challenge alone. The benefits of wildfire resilience are shared across communities, governments, insurers, investors, utilities and businesses. A single intervention can protect homes and livelihoods, reduce insurance claims, secure water supplies and lower future public costs. Because the benefits are shared, the solutions must be too. Coalitions of actors can take proven approaches further than any one individual or organisation could alone.

    As wildfires continue to burn at an unprecedented scale, the opportunity now is to roll out solutions, shift investment upstream and build a future where resilience, rather than recovery, becomes the foundation of thriving economies.

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    Climate Change

    Guest post: Why tough methane cuts are crucial for keeping warming ‘well-below’ 2C

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    Methane is a powerful greenhouse gas and the second-largest contributor to global warming after carbon dioxide (CO2).

    Methane traps heat in the atmosphere more efficiently than CO2, but has a significantly shorter lifespan, fading after just a few decades.

    Therefore, reducing emissions of methane – a gas primarily produced by agriculture, fossil fuels and waste management – is a powerful option for limiting global warming in the near-term.

    Yet climate strategies and models often only focus on CO2, or combine all greenhouse gases into one metric known as “CO2 equivalent”.

    The latter approach makes reducing methane emissions dependent on modelling choices and assumptions about the “equivalence” of methane and CO2.

    It hides the opportunities and challenges linked to methane’s high warming and short lifetime.

    In a new study, published in Communications Earth & Environment, we offer a different perspective that “decouples” CO2 and methane reduction and takes global warming limits as a starting point for determining the required level of methane cuts.

    We show that, even under the most ambitious existing national net-zero targets, an absence of methane reduction leads to peak warming that exceeds 1.85C above pre-industrial levels.

    The study highlights that, to limit peak warming to well-below 2C, net-zero CO2 targets must be complemented by stringent methane emissions cuts.

    CO2 equivalent

    How much methane corresponds to one tonne of CO2?

    The question is as difficult to answer as: ‘how much spaghetti equals a chicken?’ You could compare the two meals according to their calories, protein content or cost. Each metric can be convenient, but is only valid for that specific comparison – no amount of spaghetti is the same as a chicken.

    The same is true for the conversion of emissions of methane and other gases to CO2-equivalent emissions. It can be convenient, as it allows different gases to be compared or combined into a single number. This is why the metric is used in climate targets or evaluating the effectiveness of different mitigation options.

    But, because methane and CO2 have different atmospheric lifetimes and warming properties, any conversion is only valid for a chosen time horizon and a chosen baseline.

    Depending on the assumptions baked into calculations, methane mitigation can either appear as an immediate priority or framed as almost unnecessary.

    There are a number of metrics that scientists use to convert greenhouse gases – whether methane, hydrofluorocarbons or nitrous oxide – into CO2-equivalent emissions:

    • “GWP20” measures how much heat a greenhouse gas traps in the atmosphere over a 20-year period, relative to CO2. It emphasises urgent methane mitigation but has been criticised for its implicit discounting of future damages.
    • “GWP100” looks at a 100-year timeline. It gives more weight to long-term warming and is used in “integrated assessment models” (IAMs) used by scientists, national emission reporting to the UN and by the GHG Protocol used by companies.
    • GWP*” considers the rate of emissions, rather than warming over a fixed time horizon. Under GWP*, very limited methane reductions bring CO2-equivalent emissions to zero, meaning remaining methane emissions can be designated as causing “no additional warming”. (This interpretation remains controversial as it assumes the continuation of historical levels of warming.)

    IAMs are the tools used to generate future emissions scenarios. Because they combine CO2 and methane emissions, the impact of methane emission cuts alone is difficult to isolate in existing emission scenarios.

    IAM-generated scenarios also assume mitigation decisions driven by costs. Combinations of CO2 and methane emission pathways that are not purely cost-effective are, therefore, not represented, even though climate policy is messy and emission pathways are rarely cost-effective in the real world.

    Only a few countries – including Japan, Mexico and South Korea – specify methane mitigation targets.

    A different approach

    In our study, we separate CO2 and methane emissions and treat them as independent.

    Instead of choosing a conversion method, we suggest that states and organisations set a limit on peak global warming first, then, based on their existing net-zero targets, determine the minimum compatible methane reduction target.

    Companies and countries around the world have set net-zero targets focused on CO2, as well as those that include all greenhouse gases. As a result, our research looks at the necessary methane reductions for both types of goal. We consider scenarios where companies or countries deliver linear – in other words, steady – emissions reductions to reach net-zero.

    Using a simple climate model, we systematically combined methane and CO2 (or greenhouse gas) mitigation pathways starting in 2025 and calculated peak warming.

    The figure below shows how peak warming depends on both the year of reaching net-zero CO2 and the level of methane cuts.

    Peak global warming relative to 1850-1900 reached until 2100 (50% likelihood), for combinations of the year of global net-zero CO2 emissions (x-axis) and the change in global methane (CH4) emissions between 2020 and that year (y-axis), assuming linear trajectories. Black lines are contours of equal peak warming. The three bars on the right show independent estimates of where CH4 emissions could or would land on the same vertical scale: CH4 mitigation available at no net cost (IEA, red), the 2030 mitigation potential (Global methane status report, orange), and the current legislation scenario for 2050 (Global methane status report, purple). Adapted from Weber et al. (2026).

    The blue arrows in the figure show that to limit warming to 1.7C under a 2050 net-zero CO2 scenario, methane emissions would need to fall by at least 69% by 2050, relative to 2020.

    Our research also finds that, if an organisation or country’s 2050 net zero-target covers all greenhouse gases, its methane emissions would need to fall by 63% instead.

    However, under current policies, methane emissions are expected to increase by around 20% by 2050, relative to 2020. We find that this pathway would result in peak warming above 2C by 2050 – even if global CO2 emissions were to reach net-zero by that date (see purple bar on the right-hand side of the figure above).

    The figure also shows how, if methane emissions remained at 2020 levels and net-zero CO2 was delivered by 2040 or later, warming would exceed 1.85C. This level of warming is above what has been argued as consistent with the Paris Agreement’s “well-below” 2C limit.

    Conversely, cutting methane emissions by around one-third – in line with the Global Methane Pledge target for 2030 – could reduce peak warming by 0.15C, of which 0.05C could be delivered by interventions that come at no net cost. These are shown by the orange and red bars, respectively, on the figure above.

    The table below highlights the minimum compatible methane cuts for three different peak warming levels and net-zero CO2 or greenhouse-gas emission targets.

    Peak warming Year of net-zero CO2 emissions Year of net-zero greenhouse-gas emissions
    2050 2060 2100 2050 2060 2100
    1.7C -69% -63%
    1.8C -32% -56% -11% -47%
    2C +8% -8% -83% >50% +33% -78%

    Minimum methane emission reductions between 2020 and the year of net-zero emissions, consistent with peak warming of 1.7C, 1.8C, and 2.0C at 50% likelihood, assuming linear emission trajectories. For some net-zero targets and peak warming levels, there are no compatible methane mitigation targets (indicated by “–”).

    Remaining carbon budget

    The global carbon budget refers to the amount of cumulative CO2 emissions allowable while still meeting a particular global warming threshold.

    The 2021 climate science report from the Intergovernmental Panel on Climate Change (IPCC) and a 2023 Nature study estimated that, by 2025, the remaining carbon budget for holding warming to 2C would be around 1,000-1,150bn tonnes of CO2 (GtCO2).

    We find that these estimates are founded on the assumption of methane reductions of 27-35% by 2050, relative to a 2020 baseline. (A 2024 Communications Earth & Environment study reached similar conclusions.)

    Under the GWP* metric, where methane emissions are only cut to maintain “no additional warming”, the remaining carbon budget would be constrained. The best estimate of a 2C budget shrinks by around 30% to approximately 750GtCO2.

    Finally, if methane emissions are not cut at all in the future, our findings suggest that the remaining carbon budget for 1.7C of global warming has, in effect, already been exhausted.

    Our analysis shows how peak warming depends on both CO2 and methane reduction – and how methane-specific targets can help refine existing net-zero targets.

    Crucially, we show that complementing net-zero CO2 targets with stringent methane cuts is necessary to limit peak warming to well-below 2C.

    Weber, K. et al. (2026) Limiting warming by CO2 and methane mitigation in an expanded scenario space, Communications Earth & Environment, doi:10.1038/s43247-026-03832-1

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