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%
Government negotiators at the International Maritime Organization (IMO) in London this week look set to agree that, from 2027, the owners or operators of ships that fail to meet targets to reduce emissions from their fuel should be penalised financially.
Under a compromise proposal put forward by the chair of the talks, shipowners who fail to meet the targets for cleaner fuels will have to make up the difference through a combination of payments to those who have met the targets and money paid into a green fund administered by the IMO.
But, while all major country-negotiating blocks are engaging with this proposal, they remain divided on what these targets should be – and on how steep the penalty should be for failing to meet them.
Small island nations like the Marshall Islands want ambitious emissions-cutting targets and high fees, while some big developing countries like China, Saudi Arabia and the United Arab Emirates want weak targets and low fees.
Governments are in closed-door talks on the issues this week, hoping to reach an agreement by Friday which can be officially signed off at the next set of talks in October.
Two-tier system
The head of the IMO, Arsenio Dominguez, told reporters on Monday that he was convinced an agreement would be reached this week, dismissing the need for a back-up plan. “It’s too easy to be negative in life – that’s not me,” he quipped.
The proposed system includes two targets to reduce the amount of greenhouse gas emitted per unit of energy used – one easier to meet and one harder. Those who fail to meet one or both of these targets can either buy “surplus units” from those that meet them or buy “remedial units” from the IMO, or a combination of the two.
The IMO’s new Net Zero Fund will spend the money from the “remedial units” to clean up the maritime sector and compensate for any negative impacts of the transition on developing economies, such as increases in the price of food due to higher shipping costs. Under the current proposal, the money will not be spent on climate action outside the maritime sector.
Governments have accepted that there will be two tiers of remedial units. Ship owners or operators that fail to meet the easier “base” emissions-intensity reduction targets should have to buy more expensive remedial units. Those that fail to meet the harder stretch targets get to buy cheaper remedial units.
Shipping’s remedial units
The price of the more expensive “Tier 2” units will be somewhere between $305-600 per tonne of carbon dioxide equivalent while the cheaper Tier 1 units will be $50-150 a tonne , according to different countries’ proposals outlined in the chair’s draft text.
A proposal from “Austria et al” – which is likely to include the European Union – calls for the highest prices of $600 and $150 for Tier 2 and Tier 1 units respectively.
The “Marshall Islands et al” – likely to consist of Pacific and Caribbean Islands and some African and Central American states – wants almost as high prices of $480 and $150 a tonne.
Japan wants the next highest – $450 and $100 – followed by a proposal from Argentina, China and unnamed others of $305 and $50.
Emissions intensity targets
Governments are also split on what the emissions targets should be. The Marshall Islands and its supporters want the highest ambition, followed in descending order by the Austria-led group, Japan, China and Argentina’s supporters, and finally Saudi Arabia and the UAE’s joint proposal with the lowest.
The Marshall Islands wants the stretch goal to be 100% emissions reductions straight away. This is a variation on their original proposal of a levy, where all emissions are priced at a flat rate. All other proposals want the targets to start very low and ramp up to around 100% by 2050.
At the IMO on Monday, ministers and negotiators from five Pacific nations told reporters they were disappointed that their levy proposal was no longer being considered.
Marshall Islands ambassador Albon Ishoda said this would have been “the best option” but that his nation and its “Caribbean, African and Central American partners and allies” can support the alternative compromise proposal “only if it prices 100% of emissions from the first tonne at no less than $150 a tonne”. “That is what climate science, economic modelling and justice demand,” he said.
He added later that another “strong red line” negotiating position was that trading of credits should not be part of the agreement. The compromise proposal’s surplus units, earned by those who exceed the emissions reduction targets, are a form of credit trading while its remedial units are not.
Tuvalu’s transport minister Simon Kofe said credit trading would benefit the “bigger countries, the richer countries” which have the “capacity” to make the green transition and punish smaller, developing countries.
Asked if his group would compromise further and accept an agreement if it didn’t get 100% of the emissions targeted straight away, Ishoda said: “Compromise is a necessary process. But, at this point, we are not ready to go back home and say we couldn’t get you the 100% required – because it’s based on the science that we have always been talking about.”
Kofe noted that an impact assessment carried out by the IMO found that a levy on all emissions was fairer, cheaper and more effective than other options under consideration. At the time this study was published last August, Brazil and Argentina labelled it “unacceptable” and “nonsensical”.
But Kofe called for compromise. “The nature of the challenge that we face right now is we can’t have China not being part of the solution or the US or the bigger countries. It has to be reached by consensus,” he said.
“I hope that we can try and appeal to the better conscience – the solution that we’re finding is for humanity not just for ourselves.”
The post Governments set to agree fees for ships that miss green targets appeared first on Climate Home News.
Governments set to agree fees for ships that miss green targets
Climate Change
Analysis: Nearly 60 countries have ‘dramatically’ cut plans to build coal plants since 2015
Nearly 60 countries have drastically scaled back their plans for building coal-fired power plants since the Paris Agreement in 2015, according to figures released by Global Energy Monitor (GEM).
Among those making cuts of 98% or more to their coal-power pipeline are some of the world’s biggest coal users, including Turkey, Vietnam and Japan.
The data also shows that 35 nations eliminated coal from their plans entirely over the past decade, including South Korea and Germany.
Global coal-fired electricity generation has increased since 2015 as more power plants have come online.
But the data on plants in “pre-construction” phases in 2024 shows what GEM calls a “dramatic drop” in proposals for future coal plants.
The number of countries still planning new coal plants has roughly halved to just 33, with the proposed capacity – the maximum electricity output of those proposed plants – dropping by around two-thirds.
China and India, the world’s largest coal consumers, have also both reduced their planned coal capacity by more than 60% over the same timeframe, from a total of 801 gigawatts (GW) to 298GW.
However, both countries still have a large number of coal projects in the pipeline and, together, made up 92% of newly proposed coal capacity globally in 2024.
‘Dramatic drop’
The Paris Agreement in 2015 had major implications for the use of fossil fuels. As the fossil fuel that emits the most carbon dioxide (CO2) when burned, coal has long been viewed by many as requiring a rapid phaseout.
The Intergovernmental Panel on Climate Change (IPCC) and the International Energy Agency (IEA) both see steep declines in “unabated” coal use by 2030 as essential to limit global warming to 1.5C.
But coal power capacity has continued to grow, largely driven by China.
Global capacity hit 2,175GW in 2024, up 1% from the year before and 13% higher than in 2015, according to GEM’s global coal-plant tracker.
This growth disguises a collapse in plans for future coal projects.
GEM’s latest analysis charts a decade of developments since the Paris Agreement and the “dramatic drop” in the number of coal plant proposals.
In 2015, coal power capacity in pre-construction – meaning plants that had been announced, or reached either the pre-permit or permitted stage – stood at 1,179GW.
By 2024, this had fallen to 355GW – a 70% drop. This indicates that countries are increasingly turning away from their earlier plans for a continued reliance on coal.
In total, 23 nations reduced the size of their proposals over this period and another 35 completely eliminated coal power from their future energy plans. Together, these 58 countries account for 80% of global fossil fuel-related CO2 emissions.
The chart below shows these changes, with China and India shown on a different x-axis due to the scale of their proposals. (See section below for more information.)
2015 to 2024, gigawatts (GW), in all countries that saw declines over this period. Red arrows indicate countries that no longer have any plans to build coal power plants. Source: Global Energy Monitor.
According to GEM, of the coal plants that were either under pre-construction or construction in 2015, 55% ended up being cancelled, a third were completed and the remainder are still under development.
Many of the nations that have phased coal out of their electricity plans are either very small or only had modest ambitions for building coal power in the first place.
However, the list also includes countries such as Germany and South Korea. These nations are both in the top 10 of global coal consumers, but their governments have committed to significantly reducing or, in Germany’s case, phasing out coal use by the late 2030s.
Turkey, Vietnam and Japan are among the big coal-driven economies that are now approaching having zero new coal plants in the works. All have around 2% of the planned capacity they had a decade ago.
Other major coal consumers have also drastically reduced their coal pipelines. Indonesia, the fifth-biggest coal user, has reduced its coal proposals by 90% and South Africa – the seventh-biggest – has cut its planned capacity by 83%.
Of the 68 countries that were planning to build new coal plants in 2015, just nine have increased their planned capacity. Around 85% of the planned increase in capacity by these nations is in Russia and its central Asian neighbours.
China and India
China is by far the world’s largest coal consumer, with India the second largest.
There was 44GW of coal power added to the global fleet last year. China was responsible for 30.5GW of this while retiring just 2.5GW, and India added 5.8GW while retiring 0.2GW.
Between them, these nations contributed 70% of the global coal-plant construction in 2024.
Nevertheless, there were signs of change as newly operating coal capacity around the world reached its lowest level in 20 years.
China and India have also seen significant drops in their pre-construction coal capacity over the past decade.
In 2015, China had 560GW of coal power in its pipeline and India had 241GW. Both nations have seen their proposed capacity drop by more than 60% to reach 217GW and 81GW, respectively.
While this is a significant reduction, both nations still have more coal capacity planned now than any other nation did in 2015. China’s current 217GW is roughly four times more than the 57GW Turkey was planning at that time.
GEM attributes the “slowdown” in China’s new proposals to the nation’s record-breaking solar and wind growth, which saw more electricity generation capacity installed in 2023 and 2024 than in the rest of the world combined.
As for India, GEM says the “notable declines” in coal proposals and commissions came after a “coal-plant investment bubble that went bust in the early 2010s”.
It notes that India is now “encouraging and fast-tracking the development of large coal plants”. The government has cited the need to meet the large nation’s growing electricity demand, especially due to the increased need for cooling technologies during heatwaves.
As other nations move away from the fossil fuel, coal capacity is likely to become increasingly concentrated in these two nations. Together, they made up 92% of the 116GW in newly proposed capacity last year.
The post Analysis: Nearly 60 countries have ‘dramatically’ cut plans to build coal plants since 2015 appeared first on Carbon Brief.
Analysis: Nearly 60 countries have ‘dramatically’ cut plans to build coal plants since 2015
David Attenborough’s voice has been a powerful guide for millions, educating audiences on the wonders of the natural world and the urgent need to protect it. His latest documentary, Ocean with David Attenborough, highlights the majesty and fragility of our ocean. The documentary is a breathtaking reminder of the deep connection between humanity and the ocean, while urging us to take action to safeguard these vital ecosystems. With a global Ocean Treaty on the horizon, this documentary calls for collective action to preserve the ocean that sustains life on Earth.
“This is the story of our ocean. And how we must write its next chapter together. For if we save the sea, we save our world. After a lifetime of filming our planet, I’m sure that nothing is more important.”
-David Attenborough
The powerful documentary film from Silverback Films and Open Planet Studios is set for release as a global cinema event from 8 May (2025), which also coincides with David Attenborough’s 99th birthday. The film will be available on streaming services globally on world oceans day on the 8th of June.
The film’s release is timed ahead of World Ocean Day (8 June 2025), June’s United Nations Ocean Conference 2025 where it will be screened (9 June – 13 June) in Nice, France, and midway through the United Nations Decade of Ocean Science for Sustainable Development (2021-2030). As world leaders decide the fate of our ocean, Ocean with David Attenborough will show why ocean recovery is vital for stabilising our climate and securing a healthier future for us all, and how marine protection – if immediately implemented – can help to turn the tide.
The Ocean’s Vital Role in Our Planet’s Health
Overfishing, plastic pollution, rising temperatures, and habitat destruction are pushing marine life to the brink. In The Ocean: A Journey with David Attenborough, viewers are invited to witness the wonders of the ocean, from its deepest trenches to its vibrant coral reefs. The film is not just a visual spectacle but also an urgent call for action. Attenborough’s narration, as always, blends awe with concern, urging us to recognise the ocean’s importance and the urgency of preserving it.
“My lifetime has coincided with the great age of ocean discovery. Over the last hundred years, scientists and explorers have revealed remarkable new species, epic migrations and dazzling, complex ecosystems beyond anything I could have imagined as a young man. In this film, we share some of those wonderful discoveries, uncover why our ocean is in such poor health, and, perhaps most importantly, show how it can be restored to health. This could be the moment of change. Nearly every country on Earth has just agreed, on paper, to achieve this bare minimum and protect a third of the ocean. Together, we now face the challenge of making it happen.”
-David Attenborough
Why the Global Ocean Treaty Matters
The Global Ocean Treaty is more than just an environmental issue—it is a matter of global responsibility. All waters of the ocean are interconnected, and its health directly affects all of us. Climate change, pollution and overfishing are pushing the ocean to the brink of collapse. Food security and the livelihoods of billions of people hang in the balance.
After years of campaigning, the first ever Global Ocean Treaty was passed at the UN in 2023, but governments now need to sign it into law, to make protected areas a reality at sea. Time is running out, and reaching this target will require a strong and urgent political response.
Australia has signed but not ratified the Global Ocean Treaty. See the list of countries that have signed and/or ratified the high seas treaty here. The new government must prioritise ratifying as a matter of urgency.
Greenpeace’s call for action is clear: to ensure the protection of 30% of the world’s ocean by 2030. We are pushing for at least 60 countries to ratify by the end of 2025 in order to support the creation of marine protected areas that are off-limits to destructive activities like deep-sea mining and industrial fishing.
In our own backyard, industrial fishing and pollution is putting immense strain on unique and diverse ecosystems. That’s why Greenpeace is campaigning to establish a marine sanctuary in the Tasman Sea.
Our beautiful blue backyard, the Tasman Sea between Australia and New Zealand has complex topography and nutrient-rich currents in these areas that create ideal conditions for species like tuna, whales, seabirds, and ancient corals to thrive. Establishing a sanctuary here would not only safeguard endangered species, like the South Pacific humpback whale and several types of albatross, but also provide a habitat for all marine life to thrive.
The Global Ocean Treaty is an essential tool for protecting life in the high seas. By creating new sanctuaries we can protect the ocean for the future. Join Greenpeace in advocating for the Australian Government to be a leader in protecting the ocean.
Together, we can protect the ocean that sustains us all.
David Attenborough’s New Documentary: A Call for Action on the Global Ocean Treaty
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