Cities are an often overlooked as being a major contributor to climate change. Yet their diversity has made it hard to assess how far they can cut their emissions.
Moreover, efforts to tackle their emissions, such as those from urban transport, often come with trade-offs in terms of costs and co-benefits from cleaner air or health.
In our new study, published in Nature Sustainability, we conducted a comprehensive analysis of transport policies in 120 cities, spanning five continents.
We found that the cities could cut carbon dioxide (CO2) emissions by a combined 22%, without cutting residents’ quality of life measured via an aggregate, monetised metric.
In individual cities, we found that a combination of policies, such as fuel taxes, public transport improvement and urban planning, could reduce transport CO2 by up to 31%.
Cities in climate policies
Cities bear a major responsibility for climate change, as they account for 70% of global emissions.
They can also play a key role in implementing climate action at the local level. Many cities have set ambitious climate goals, with members of the Global Covenant of Mayors city network, for instance, aiming to reduce their emissions by 66% by 2050.
Urban transport, in particular, is an important sector, representing 8% of global emissions alone. This also tends to be an area where cities have the ability to act.
Yet, quantifying the aggregated potential of cities to mitigate transport emissions has proven challenging. Indeed, the impacts of city-level policies depend on the unique characteristics of each city, such as urban spatial organisation and existing infrastructure.
On the other hand, detailed city models applied to case-study cities are difficult to generalise, since the scientific literature is fragmented and biased toward larger cities and developed countries.
Exploring strategies
Using an urban simulation model, we estimated the aggregate potential for 120 cities on five different continents to reduce their urban transport emissions.
We also considered the impact of such climate actions on inhabitants’ quality of life, through housing and transport prices, local taxes and health co-benefits related to transportation. This included those related to cleaner air, reduced noise, reduced traffic accidents and increased physical activity due to active transportation modes.
The 120 cities are home to 525 million inhabitants, or about 20% of the total global population that lives in cities larger than 300,000 people.
To calibrate the model on each city, we relied on spatially explicit socio-economic data that we collected through web-scraping of local websites, as well as data on local transportation systems that was provided by Open Street Map, Google Maps and Baidu Maps.
Our study explores four main types of complementary strategies that could help reduce transport-related emissions in cities: taxation of polluting vehicles; incentives to use vehicles that consume less fossil fuel; investment in public transport; and urban planning policies that restrict urban sprawl.
For each of these strategies, we examined examples of public policies that can be implemented at local level. For example, to improve public transport, one possibility is to set up a bus rapid transit system on dedicated lanes.
Other examples include that urban planning can involve limiting new construction away from public transport stations. Polluting vehicles can be taxed by raising fuel prices or by introducing local congestion charges.
Finally, the use of more efficient vehicles, such as electric cars, can be encouraged by a combination of subsidies and bans on the most polluting vehicles in urban centres.
Comparing local policies
Our findings suggest that a combination of these policies could reduce overall transportation GHG emissions by up to 31% in 15 years, across the 120 cities studied.
Policies implemented individually could mitigate emissions by 4% to 12%, depending on the policy considered.
These results are in line with the scientific and “grey” literature on the topic, which has shown that urban transport emissions could be mitigated by 20% to 25% through a combination of urban planning and technological solutions.
The impact of a given policy varies according to the city in which it is implemented. For example, in the majority of South American cities studied, the introduction of new public transport lines would be particularly beneficial, our results suggest.
Given the relatively high population density and underdeveloped public transport systems in these cities, our simulations indicate that the implementation of new public transport lines could potentially reduce emissions by up to 21% and 26% in Brazilian cities such as Goiânia and Belém, respectively.
In Europe, taxing fuel prices appears to be more effective, primarily due to the generally well-developed public transport networks available in European cities. For instance, a fuel tax would lead to a 7.5% reduction in transport-related emissions in Barcelona, we found, while the impact would be only 0.6% in Atlanta (USA), where alternatives to private cars are less readily accessible.
Simultaneous implementation of multiple policies can have a particularly significant impact, our results show. Combining taxes on polluting vehicles with public transport development could result in substantial emission reductions, as could promoting public transport alongside measures to control urban sprawl and increase population density near railway stations.
For instance, in Lille (France), implementing policies to control urban sprawl, tax polluting vehicles and develop public transport concurrently would potentially reduce transport-related emissions by almost 24%, compared to reductions of 9%, 4%, and 7%, respectively, if each policy was implemented individually.
An example of the differing impact of public transport development on CO2 emissions after 15 years can be seen in the map below, with purple circles showing cities that could achieve a more than 10% saving, blue showing 5-10%, green 1-5% and yellow less than 1%.
Variation in transport-related CO2 emissions
Inhabitants’ quality of life
Assuming that these policies are fully financed locally by a tax, our study also estimates their impact on the material conditions of residents and on their health.
We analysed the impacts of urban transport emission reduction policies on a range of factors linked to quality of life. In terms of income, for example, building locally financed public transit lines increases local taxes, while taxing polluting vehicles reduces them. We also looked at transportation costs, average housing prices, air quality, noise pollution, road accidents and the health benefits associated with “active” mobility (walking or cycling instead of driving).
Depending on the city, these impacts can be positive or negative overall. A fuel tax or the opening of new public transport lines would be expected to improve air quality, reduce noise pollution and the number of road accidents. More efficient vehicles improve air quality and reduce the household transport budget – even if their impact in terms of road accidents remains unchanged.
On the other hand, urban planning that limits urban sprawl can contribute to higher housing prices and the introduction of public transport lines can sometimes prove extremely costly.
To facilitate comparison, we expressed these variations in monetary terms, creating a composite indicator of welfare that encompasses all dimensions of residents’ quality of life mentioned earlier, as shown in the figure below.
Our study reveals that, in all cities examined, there are policy combinations that can effectively reduce emissions while improving overall well-being.
Most importantly, if, in each of the 120 cities of our sample, instead of applying all the policies that we considered, we choose to apply only policy combinations which do not reduce our monetised measure of welfare, we find that we can reach in total a 22% reduction in urban transportation GHG emissions in 15 years.
This means that most of the emission reductions that we simulate in our study can be reached without affecting residents’ quality of life in any of the cities that we considered.
While 22% is not sufficient, in itself, to reach carbon neutrality, we only analysed four simple and generic policies. Specifically designed and optimised policy portfolios for each city could reach larger emission reductions.
Climate governance and research
As numerous protests worldwide have demonstrated, public policies aimed at reducing emissions must also positively impact residents’ quality of life to gain acceptance.
In all the cities that we studied, we found that it is possible to combine reduction of GHG emissions and the enhancement of quality of life, through well-adapted policy choices.
In order to achieve this, the set of policies needs to be tailored to each city’s specificities, however, with strategies which cannot necessarily be directly transposed from one city to another. In our city sample, the emission reduction that can be reached – even with a generic policy toolkit – is also significant.
Cities are frequently overlooked in international climate discussions, in part because of the diversity of their characteristics. This diversity does make it difficult to assess the potential of urban policies to contribute to global climate goals.
With the recent increases in local urban data becoming available, however, our study shows that it is now possible to explicitly model and assess the consequences of climate strategies over a wide range of cities.
Important research gaps still remain. We could not, for instance, include any African cities in our sample due to challenges accessing reliable and comparable data. If current trends in data availability continue, this and other issues could be solved over the coming years.
The post Guest post: How 120 of the world’s major cities could cut transport CO2 by 22% appeared first on Carbon Brief.
Guest post: How 120 of the world’s major cities could cut transport CO2 by 22%
Bo French prevailed over incumbent Jim Wright after a primary campaign focused more on Islamophobia and deportations than oil and gas regulation.
Bo French has won the Republican nomination to help run a little-known but influential regulatory office in Texas that oversees the state’s oil and gas industry.
Hardline Conservative Wins Republican Primary for Texas Oil and Gas Regulator
China has said that hydrogen is a key “future industry”, important to both its energy transition and its industrial policy.
Hydrogen frequently goes through hype cycles, most recently driven by rising oil and gas prices due to the conflict in the Middle East.
Yet, even in China, the world’s largest producer and consumer of the fuel, hydrogen remains expensive and inefficient to produce.
This is especially the case for “green” hydrogen derived from renewables.
Moreover, there is limited supporting infrastructure and there is little incentive to use hydrogen over other energy sources.
As a result, uptake in China of hydrogen as an alternative fuel remains low.
Nevertheless, these challenges echo the early circumstances of another key clean-energy technology – electric vehicles (EVs).
In China, EVs benefited from a policy environment that included consistent signals of support, financial aid and the development of supporting infrastructure.
Many similar policies are now being deployed – and in some cases improved upon – to support the development of China’s hydrogen industry.
This article examines China’s approach to developing hydrogen and how its evolving industrial policy could make the fuel viable.
How is China using hydrogen and where does it come from?
Electrification and rising installations of solar and wind power have been the biggest drivers of China’s decarbonisation story so far. However, how China will address the more energy-intensive, hard-to-electrify segments of its economy remains an open question.
Hydrogen is seen by some in China as a potential solution for reducing emissions in a range of “hard-to-abate” industries, from steel and chemicals to aviation and shipping.
The country is the world’s foremost producer and consumer of hydrogen. It produced 36.5m tonnes of the gas in 2024, with maximum production capacity standing at 50m tonnes that year.
It also consumed nearly a third of the world’s hydrogen in 2024, as shown below.
Most of China’s production capacity is in regions with potential for high demand, such as Shandong, Inner Mongolia, Shaanxi, Ningxia, Shanxi and other provinces with significant heavy industry.
In 2024, the vast majority of China’s hydrogen – around 78% – was produced using fossil fuels, predominantly coal and gas, as shown in the figure below.
Another 21% was produced as an industrial by-product, while only 1% – just 320,000 tonnes – was derived from renewable-powered electrolysis of water.
One study found that, for every kilogram of hydrogen produced, 38.6kg of carbon dioxide (CO2) is emitted if the hydrogen is produced using coal-fired power. Hydrogen made through coal gasification results in 28.5kg of CO2 for every kilogram of hydrogen, while gas-based hydrogen creates 13kg of emissions.
By contrast, one kilogram of renewables-based hydrogen results in 0.5kg of CO2.
The International Energy Agency (IEA) calculates that hydrogen and hydrogen-based fuels could help China avoid close to 16bn tonnes of CO2 cumulatively by 2060 – but only if it comes from low-carbon sources.
The biggest reductions, it adds, would come from heavy industry, particularly chemicals and steel, with the maritime and shipping sectors also seeing some benefit.
Currently, around half of the hydrogen produced in China is used in synthetic ammonia and methanol production.
Ammonia is primarily used to manufacture fertiliser and is seen as a possible fuel technology for shipping. Methanol is used as a fuel for the transport industry, as well as for heating.
Another quarter of China’s current hydrogen usage is consumed by the oil refining and coal-to-chemical sectors. The remaining amount is used in other industries, including transport, heating and metallurgy.
What are the barriers to scaling up hydrogen?
Although China is the largest producer and consumer of hydrogen globally, the industry faces several barriers to becoming a viable clean-energy technology.
Agora Energiewende, a thinktank focused on the energy sector, says that, in order to make hydrogen a practical clean-energy solution, China would need to expand the scale and range of its application, as well as improving the conversion efficiency of production and use.
Both BloombergNEF and the IEA highlight the importance of China creating demand for hydrogen, such as through quotas for industrial usage.
Hydrogen “suffers from a relatively large efficiency loss during various conversion processes”, adds Agora. For example, it notes that only around 22% of the energy put into hydrogen fuel-cell electric vehicles (FCEVs) is converted into motion, compared to 73% for battery electric vehicles. Producing hydrogen with renewable energy is also less efficient than coal-to-hydrogen processes.
Cui Chuansheng, technical director at East China Engineering Science and Technology, tells state news agency Xinhua that the variability of wind and solar power often leads to low utilisation of electrolysers, resulting in “efficiency losses”.
Meanwhile, the cost of producing hydrogen – particularly green hydrogen – remains high.
One study placed the cost of hydrogen produced through alkaline water electrolysis (AWE), the most common method for producing green hydrogen in China, at $4-6 per kilogram, compared with $1.20-2.50/kg for steam methane reforming and $1.30-2 for coal gasification.
In some specific cases, such as blending hydrogen with gas, researchers find that hydrogen prices would need to fall to one-third of gas prices to incentivise uptake.
These constraints are all “interdependent”, Kevin Tu, managing director of Agora Energy China, tells Carbon Brief, with the need to ensure “bankable demand” while also reducing costs and developing infrastructure. He adds:
“Without credible offtake in the right sectors, costs will not fall; without lower costs and better logistics, downstream users will not commit.”
The IEA says that green hydrogen “could become cost-competitive by the end of this decade due to low technology costs and cost of capital”.
For now, however, the China Hydrogen Bulletin Substack reports that China’s four listed hydrogen equipment manufacturers all reported significant losses in 2025.
Meanwhile, a senior executive at a Chinese hydrogen company told economic news outlet Jiemian that he expected 40% of companies in the sector to have closed down by the end of 2026, with surviving companies only turning a profit in 2029 at the earliest.
The industry also lacks refueling and pipeline infrastructure. China’s development of a pipeline network for hydrogen remains in its early stages, with around 400km of pipelines currently in operation. By contrast, its long-distance gas network stands at 128,000km. Similarly, storage remains expensive and inefficient, creating a further obstacle to wider uptake.
How is China supporting hydrogen development?
China began considering the use of hydrogen as an energy source in earnest in the early 2000s, to address concerns around pollution and dependence on imported oil for the transport sector.
A clearer signal of its importance came in 2015, when the State Council included the technology in a 10-year national industrial strategy known as the “Made in China” initiative. This pitched hydrogen as a way to contribute to electrification of China’s road-transport system through the development of FCEVs.
Yuki Yu, founder of research firm Energy Iceberg, tells Carbon Brief that, from 2018-2021, hydrogen was treated as a “FCEV and manufacturing technology challenge”.
This has since evolved, she says, given that battery electric vehicles have emerged as the more popular technology.
Shen Xinyi, senior advisor at the Centre for Research on Energy and Clean Air (CREA), agrees, telling Carbon Brief that recent policy documents suggest the aim is now for hydrogen to be targeted at areas where direct electrification is harder, such as hydrogen-based chemicals, hydrogen metallurgy and some heavy-duty transport applications.
This is in line with the “hydrogen ladder”, an analysis of how likely different possibilities for applying hydrogen as a clean alternative are to become significant. The ladder sees significant future use of hydrogen in these hard-to-electrify areas as much more likely than for light vehicles.
Notable policy moves are being made in “three layers”, says Agora’s Tu, which are combining to improve the technology’s chances of scaling up. These are: the “legal and institutional” layer; “application-oriented” policies; and targeted measures to address “practical bottlenecks” at the local level.
One of the documents underpinning this pivot was the “medium- and long-term plan for the development of the hydrogen energy industry (2021-2035)”, issued in March 2022.
According to a report by the National Energy Administration (NEA), the plan is an attempt to develop an “industrial ecosystem” for hydrogen that features “diverse stakeholders, coordinated innovation and clustered development”.
The plan was the first government document to “lay out a long-term vision for China’s hydrogen economy”, unifying a previously disparate policy push into one document, according to the Oxford Institute for Energy Studies, a UK-based thinktank.
Following on from the 2022 plan, the importance of hydrogen as a broad clean-energy solution has been emphasised in a number of policies. These include its classification being changed from a hazardous chemical to an energy carrier in China’s Energy Law, a 2024 action plan to “accelerate” the use of low-carbon hydrogen in industry and a new pilot scheme offering subsidies for projects that achieve specific targets.
The table below sets out the timeline and content of China’s hydrogen-related policies over the past 25 years.
| Policy | Year published | Key features |
|---|---|---|
| 10th five-year plan (2001–2005) | 2001 | Calls for “actively developing” low-emission vehicles, understood to include hydrogen vehicles |
| Made in China 2025 | 2015 | Pledges to “continue to support” development of fuel cell vehicles and “master core technologies” for low-carbon vehicles |
| Notice on implementation of demonstration projects for fuel cell vehicles | 2020 | Creates a dedicated subsidy programme for finding breakthroughs in FCEV core technologies and industrial applications |
| 14th five-year plan (2021-2025) | 2021 | Hydrogen listed as a future industry |
| Medium- and long-term plan for the development of the hydrogen energy industry (2021–2035) | 2022 | Aims to reach 100,000-200,000 tonnes of green hydrogen production [this target has been met]. Also aims to get 50,000 FCEVs on the road by 2025, leading to a “diversified” hydrogen industry by 2035 |
| Opinions on accelerating the comprehensive green transformation of economic and social development | 2024 | Promotes further development of hydrogen production, transport, storage and applications |
| Implementation plan for accelerating the application of clean and low-carbon hydrogen in the industrial sector | 2025 | Outlines tasks to promote use of low-carbon hydrogen to reduce emissions in heavy industries, such as steel and chemicals |
| Energy law | 2025 | Sees hydrogen included in national legislation for the first time, re-classifies it from a hazardous chemical to an energy carrier |
| 15th five-year plan (2026-2030) | 2026 | Again lists as a future industry, and calls for the development of green fuels derived from green hydrogen |
| Notice on the implementation of pilot projects for the comprehensive application of hydrogen energy | 2026 | Provides subsidies to projects to reduce hydrogen costs to 15-25 yuan/kilogram ($2.20-3.67/kg) and help develop a fleet of 100,000 FCEVs |
Key policies in the development of China’s hydrogen sector.
In addition, the NEA said in 2025 that local governments across China had issued more than 560 hydrogen-related energy policies by the end of 2024.
Tu notes that these local policies cover everything from permitting reforms and pipeline planning to exempting FCEVs from paying road toll.
Different provinces across China adopt distinct strategies for developing hydrogen industries, based on local conditions, says the US-based Center on Global Energy Policy, such as energy mix, availability of coal and industrial needs.
However, these local policies and targets are frequently more ambitious than the “conservative” national-level targets, it adds.
Could a new pilot programme boost hydrogen’s prospects?
A new pilot programme, announced in March 2026, aims to commercialise the country’s hydrogen industry by funding projects to reduce the cost of the fuel to 15-25 yuan/kilogram ($2.20-3.67/kg) by 2030, as well as other targets.
Unlike the 2020 subsidies, which focused on FCEVs, the new programme reaffirms China’s interest in a broader series of sectoral applications for hydrogen, including in clean heating, production of low-carbon iron and steel, and production of “green fuels” and other chemicals.
This new pilot is the “strongest financial instrument ever released for China’s green hydrogen application” in terms of creating a comprehensive hydrogen policy that covers a broad swathe of the economy, supporting it with financial backing and targeting application scenarios, Yu says.
However, she argues that strict grant caps – 240m yuan ($35m) per project and 1.6bn yuan ($235m) per selected region across only five regions – limited the overall funding scale available to the industry.
Energy Iceberg has calculated that only around 60-70 projects nationally could receive funding under the current rules, out of more than 670 active green hydrogen proposals in China.
Shen agrees that the pilot programme is significant and that it will expand the use of hydrogen in China’s climate strategy, particularly green hydrogen.
She notes a provision that “explicitly states that coal-based ammonia and methanol projects cannot be labelled as ‘green’ ammonia or methanol”, suggesting that policymakers are increasingly paying attention to the “integrity” of definitions for hydrogen and hydrogen-derived fuel.
The “real value” of the pilot scheme, says Tu, is that it focuses on developing “integrated city-cluster ecosystems linking supply, transport, infrastructure and end-use demand”, rather than only supporting individual projects.
This “should help identify viable business models, accelerate cost discovery and concentrate support on applications with stronger scale potential”, as well as boost investor confidence, adds Tu.
However, he continues that the broader effect it will have on boosting production of hydrogen will “depend on how quickly the selected clusters can translate the programme into real offtake and lower delivered hydrogen prices”.
How does this compare to China’s EV policy push?
The debate around the viability of hydrogen is reminiscent of critiques of EVs.
Until recently, EVs were seen as too expensive for consumers, inefficient and challenging to use without supporting infrastructure. As a result, many western automakers chose to temper their focus on EVs, while continuing to develop internal combustion engines.
However, China has managed to develop a competitive EV industry with products that top global sales.
Part of the playbook that spurred China’s success on EVs included consistent policy signalling in favour of the technology, including mentions in high-level documents and committing resources to building charging infrastructure.
“The defining features of China’s industrial-policy success are its persistence and adaptability,” says Kyle Chan, fellow at the Brookings Institution, adding that “long before the technology and economics of EVs and batteries were proven, China was making long-term investments and policy bets [in the sectors]”.
More tangible measures included direct and indirect subsidies and policy support in the shape of favourable loan rates and low-cost land. One estimate by US-based thinktank the Center for Strategic and International Studies (CSIS) pegs the amount of support allocated to the EV industry between 2009-2023 at $230.9bn.
This coupled with the success of private Chinese manufacturers in creating innovative, nimble companies that “forc[ed] policymakers to adapt”, as well as growing links between the automotive and information technology industries, according to a separate CSIS report.
But this progress on EVs also reportedly came with significant fraud. In 2016, one investigation found that 33 companies were involved in subsidy fraud totalling 9.2bn yuan ($1.3bn).
(It should also be noted that profitability in the industry lags far behind the average for downstream industrial sectors, according to the Hong Kong-based South China Morning Post, which says that “only a handful” of nearly 50 EV makers have reported profits.)
Being the subject of an industrial policy push alone does not guarantee success, states CSIS. It says the strength of the EV industry “was neither inevitable nor the result of a single master plan” and that China’s aims to develop globally-competitive industries in areas such as commercial aviation remain unaccomplished.
China’s approach to hydrogen has been markedly different.
Instead of offering blanket subsidies, the fuel cell demonstration programme it established in 2020 focused on performance-based rewards.
To avoid the subsidy issues seen in the solar and EV industries, the ministry of finance deliberately chose this indirect funding model, says Yu.
However, Yu argues, the programme did not work as well as hoped, due to the funding ceiling and the siloed attempts made by different regional governments to develop hydrogen ecosystems .
But Chinese policy thinking is becoming more selective and pragmatic for hydrogen compared with EVs, says Shen. She says:
“Electrification remains the primary decarbonisation pathway [for road transport], while hydrogen is increasingly positioned for applications where direct electrification is more difficult.”
Tu echoes this, adding that China is “clearly moving toward a more supportive policy environment for hydrogen”.
But its approach is “unlikely to replicate the EV story one-for-one”, he adds.
China’s concerted hydrogen push is also unlikely to echo the EV story at a global level, according to the IEA.
In terms of green hydrogen, around 60% of global electrolyser manufacturing capacity is currently in China, prompting concerns from the EU about a repeat of China’s global dominance in the solar and EV sectors.
However, the IEA says, electrolysers made in China “might not supply other markets at scale in the short term”, due to difficulties transporting the bulky technology globally, expectations that costs will only fall gradually, uncertainty around global demand and questions over how well Chinese electrolysers perform against global alternatives.
China’s industrial focus on hydrogen is centred more on domestic use, Shen argues. “It is less about near-term export competitiveness and more about building domestic industrial ecosystems,” she says.
The post Q&A: Can China turn hydrogen into its next clean-energy industry? appeared first on Carbon Brief.
Q&A: Can China turn hydrogen into its next clean-energy industry?
Climate Change
In Venezuela, Anxiety About Ramping Up Oil Production in the Heavily Polluted Lake Maracaibo Region
Experts and local activists, wary of past exploitation, are hoping it will be different this time—but aren’t confident it will be.
There is a joke Mónica Godoy Molero likes to make with her family: if you swim in Venezuela’s Lake Maracaibo after an oil spill, you’ll sprout a third eye.
In Venezuela, Anxiety About Ramping Up Oil Production in the Heavily Polluted Lake Maracaibo Region
Hardline Conservative Wins Republican Primary for Texas Oil and Gas Regulator
Q&A: Can China turn hydrogen into its next clean-energy industry?
In Venezuela, Anxiety About Ramping Up Oil Production in the Heavily Polluted Lake Maracaibo Region
-
Climate Change10 months ago
Guest post: Why China is still building new coal – and when it might stop
-
Greenhouse Gases10 months ago
Guest post: Why China is still building new coal – and when it might stop
-
Greenhouse Gases2 years ago嘉宾来稿：满足中国增长的用电需求 光伏加储能“比新建煤电更实惠”
-
Climate Change2 years ago嘉宾来稿：满足中国增长的用电需求 光伏加储能“比新建煤电更实惠”
-
Climate Change2 years ago
Bill Discounting Climate Change in Florida’s Energy Policy Awaits DeSantis’ Approval
-
Renewable Energy7 months agoSending Progressive Philanthropist George Soros to Prison?
-
Carbon Footprint2 years agoUS SEC’s Climate Disclosure Rules Spur Renewed Interest in Carbon Credits
-
Greenhouse Gases11 months ago
嘉宾来稿：探究火山喷发如何影响气候预测