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%
The United Nations Secretary-General and foreign ministers from the UK, France and Spain have blamed the deadly wildfires engulfing Europe on climate change, using the disaster to renew calls for faster cuts to greenhouse gas emissions.
António Guterres told journalists on Friday that the “climate crisis is in overdrive”, adding that global heat seen so far is just a “warm up act” as a phenomenon known as El Niño intensifies “adding fuel to a planet already on fire”.
A new World Meteorological Organisation (WMO) report published on Friday predicts that the weather pattern will grow into a “strong event” between now and October, increasing the risk of higher than normal temperatures across much of the world and disrupted rainfalls.
“That risks shattering every seasonal record – and driving even more severe effects worldwide,” Guterres said.
El Niño builds on top of an already warming world, driven primarily by the burning of fossil fuels. A WMO scientist, who did not want to be named, told journalists that all the heatwaves and other climate impacts seen so far this year are “before the effects of El Niño are really kicking in at a global scale”.
Fossil fuellling the fires
Fires have broken out across much of Europe but are threatening the most people in the south-west of France near Bordeaux and in Central Spain near Madrid. Nearly a quarter of a million people have been evacuated in France with hundreds of homes destroyed while in Spain 80,000 people have had to leave their homes and at least 13 died in one village.
A scientific study published on Friday by the World Weather Attribution group found that man-made climate change made deadly fires in France twice as likely and those in Spain twenty times more likely. Smaller fires in the UK were not analysed by the study.
UN Climate Change leader Simon Stiell blamed fossil fuels for the fires, as well as storms in Chile and heatwaves in North America and Japan in recent weeks. “The climate alarm is blaring”, he said on Wednesday.
Guterres criticised new fossil fuel production projects and fossil fuel subsidies for causing hardship across the world. Discussing his speech, a senior UN official – who did not want to be named – said the subsidies amounted to trillions of US dollars a year and criticised pension funds and institutional investors, including insurance companies, for continuing to invest in fossil fuel projects.
Asked why world leaders and the public are not prioritising climate action, Guterres said they are distracted by wars in Ukraine, the Middle East, Sudan and elsewhere and sometimes forget “other aspects that are a sometimes even more dangerous threat”.
Also the fossil fuel industry and “some countries” are campaigning to pretend that climate change does not exist, he said, adding that the UN should be more active in “naming the situations as they are and the responsibilties as they are and mobilising the public opinion”.
After meetings in Paris and Madrid earlier in the week, the UK’s new foreign minister Ed Miliband issued joint statements with his French and Spanish counterparts – Jean-Noël Barrot and José Manuel Albares Bueno – calling on the world to reduce its dependence on fossil fuels.
They promised to do more to reduce emissions and protect their people and encouraged other governments to do the same.
The UK-French statement called on governments to publish UN climate plans, known as nationally determined contributions (NDCs), which are aligned with the Paris Agreement’s goal to limit global average temperatures to 1.5C above pre-industrial levels.
According to Climate Action Tracker, only three countries – the UK, Nigeria and Norway – have submitted NDCs with 2035 emissions reduction targets which are compatible with 1.5C. Fifty-two countries – including Egypt, Vietnam and Argentina – have yet to submit an NDC at all.
Defending science
Beyond action on emissions, the ministers also intervened in an ongoing dispute over the timing of the Intergovernmental Panel on Climate Change’s (IPCC)’s next flagship assessment.
Miliband and Barrot’s statement said they “underline the importance” of scientific report feeding into governments’ next global stocktake of progress on climate action in two years’ time, calling it a “critical input” to that process.
The timing of this report has been a contentious issue in government negotiations at the IPCC and at June’s climate talks in Bonn. While a group of nations calling themselves the “friends of science” want the report before the stocktake, others like Saudi Arabia and India have argued that this would make the report of a worse quality and less inclusive of developing countries’ scientists.
Science ‘under attack’ from fossil fuel interests at UN climate talks
The UK-Spanish statement weighed in less explicitly on this issue but said that they “recall the importance of scientific evidence and acknowledge the work of the IPCC in this respect.”
The British and French ministers said they would seek to accelerate reductions of emissions in methane, a particularly potent greenhouse gas, at COP31 in November. They encouraged governments “to work jointly to develop a marketplace for fossil fuels with near-zero methane intensity.”
Methane leaks from oil, gas and coal production are a major contributor to global warming. Over a 20-year period, methane traps around 80 times more heat than carbon dioxide.
The UK and Spanish statement emphasised the importance of supporting the Global South and underlined the need to mobilise sustainable financing “at scale with the challenge we face”. The previous UK government, in which Miliband was energy minister, cut climate finance to developing countries to pay for increases in military spending.
The UK government led by new Prime Minister Andy Burnham has yet to outline any major changes to climate finance in its two weeks in power but has announced it will convert some finance from grants to loans in order to free up money to subsidise bus travel in England.
More adaptation needed
Guterres said that “it is time to stop treating each disaster as an isolated tragedy and recognise the systemic risk that is unfolding before our eyes.” A recent study found that three-quarters of UK media reports about the British June heatwave did not mention climate change.
As well as reducing emissions, the UN Secretary-General called for measures to adapt vulnerable people to extreme heat. Specifically, he said that buildings should be built and retrofitted for extreme heat and that every city and country should have heat-health action plans and early warning systems. Over 250 cities have joined the UN’s ‘beat the heat’ initiative, he said.
The Portuguese diplomat called for governments and employers to do more to protect their workers from heat, criticising global fashion brands for not setting heat standards for the factories that supply them. “No one should have to risk their life to earn a living,” he said.
The post UN chief warns climate crisis “in overdrive” as El Niño threatens to fuel the fire appeared first on Climate Home News.
UN chief warns climate crisis “in overdrive” as El Niño threatens to fuel the fire
Climate Change
‘Ride the wave of momentum’: Australia announces once-in-a-decade Marine Parks Network review
In response to the federal government announcing its once-in-a-decade review of Australia’s Marine Parks Network, the following lines can be attributed to Elle Lawless, Senior Campaigner at Greenpeace Australia Pacific:
“Greenpeace Australia Pacific welcomes today’s announcement that the Albanese Government will review Australia’s Commonwealth Marine Parks Network. This is a rare, once-in-a-decade opportunity to strengthen our marine parks and ban industrial fishing in Australia’s marine protected areas.
“Australians would be appalled to know that more than half of Australia’s Marine Parks Network currently allows for extractive industries, like longlining, bottom trawling and oil and gas mining. These so-called ‘protected’ areas were designed to safeguard our beloved ocean wildlife and underwater ecosystems – that is what Australians expect. Damaging industrial industries should not be given a free pass to trawl, fish, drill or extract from our marine parks.”
“With the first Ocean COP just around the corner, and off the back of Australia’s move to ratify the Global Ocean Treaty earlier this year, the Australian government has a unique opportunity to ride the wave of this momentum and solidify itself as a true global ocean leader.
“Greenpeace Australia Pacific is calling for industrial activities to be banned from our protected waters and for at least 30% of Australia’s ocean to be protected as ocean sanctuaries. This review presents a rare opportunity to create more ocean sanctuaries, true blue havens where ocean life can recover, thrive and repopulate the surrounding waters.”
—ENDS—
‘Ride the wave of momentum’: Australia announces once-in-a-decade Marine Parks Network review
In recent days, prominent climate sceptics and rightwing commentators have shared charts on social media incorrectly implying that Europe is having its “quietest” year for wildfires in 2026.
These include Dr Matthew Wielicki, a former University of Alabama geochemist and self-described “professor in exile”, who was recently appointed by the Trump administration to lead the US Global Change Research Program.
However, these charts paint a misleading picture as they are skewed by encompassing the entirety of Russia in the data – including the vast plains of Siberia.
These charts also use data that include fires that are deliberately lit to manage cropland, which is a declining practice across much of Europe.
In this factcheck, Carbon Brief shows that the area burned by wildfires across the European Union in 2026 is second only to 2022 for this time of year.
The latest data from the European Forest Fire Information System (EFFIS) also shows that France has set a new modern record for area burned and Spain’s wildfire season is among the worst on record.
The fires have displaced more than a third of a million people across south-western Europe, while an impending heatwave has also raised fears of the fires worsening in the coming days.
‘Quietest year’
On 27 July, as wildfires raged across multiple European countries, former Conservative peer and climate-sceptic commentator Matt Ridley posted on Twitter that “2026 is the quietest year for wildfires in Europe by some distance”.
Ridley, who sits on the academic advisory council of the Global Warming Policy Foundation (GWPF), a UK-based climate-sceptic lobby group that refuses to reveal the sources of its funding, was responding to an article by Daily Telegraph columnist Tim Stanley.
Stanley’s column, headlined: “Climate change is real – and the right needs to get serious about it”, warned:
“This is no longer a matter of speculation: the wildfires of Europe, pitiless and persistent, are the way we live now.”
Ridley included a chart from Our World In Data, showing the cumulative area burned by wildfires by week for Europe. The chart puts 2026 as having the smallest area for this time of year in a dataset going back to 2012.
Ridley’s post was widely shared by prominent rightwing figures – including Richard Tice, deputy leader of the hard-right, climate-sceptic Reform UK party, former Conservative cabinet minister Jacob Rees-Mogg and multiple commentators.
Separately, Wielicki also shared a chart on Twitter to imply that wildfires in Europe are declining. Wielicki has previously claimed that the “science is not settled on climate change”.
The charts posted by Ridley and Wielicki both use data from the Global Wildfire Information System (GWIS). The GWIS category for “Europe” encompasses all the countries on the continent and includes the whole of Russia.
As a result, Russia accounts for about 74% of the area included in the GWIS definition of “Europe”.
Wildfires in Russia typically account for 80-90% of the burned area in the GWIS Europe dataset. In 2026, fires in Russia are substantially below average. Therefore, including Russia in this comparison creates the false impression that wildfire activity across Europe is unusually low.
Dr Calum Cunningham, a research fellow at the University of Tasmania’s Fire Centre, says that such claims are “highly misleading”, noting that “they rely on aggregating fire activity across an enormous and climatically diverse region”. He tells Carbon Brief:
“A relatively quiet season in Russia can easily mask an exceptionally active season in France or Spain. If the analysis is focused on the regions actually experiencing the current fires, the picture is very different.
“The reality is that western Europe has experienced an extraordinary sequence of climate conditions this year.”
In contrast, the EFFIS provides a subset of wildfire data specifically for the area covered by the 27 nations of the EU, which, therefore, excludes Russia.
Another difference between the two datasets is that GWIS monitors all fires – including those on agricultural land that are intentionally set alight. The burned area as measured by GWIS contains significant cropland area.
By contrast, EFFIS uses land-cover data and other information to filter specifically for forest fires.
Looking at the EU-only data from EFFIS reveals that Europe is far from having its “quietest” year. The bloc’s burned area, as of 29 July, is almost 435,000 hectares (ha) – second only to 2022 for this time of year.
Notably, Wielicki has actually continued to post charts based on GWIS data, even after acknowledging that “includ[ing] all of Russia, including vast areas of Siberia…isn’t a good proxy for Europe”.
French fires
Even looking at EU-wide data misses the scale of this year’s wildfires for some individual countries.
The chart below shows the surge in burned area in France since mid-July.
For much of the first half of the year, the country was having a wildfire season that was only slightly above average in terms of total burned area. However, a notable uptick began in the first week of July.
The third week of the month saw France break its previous cumulative annual record by more than 19,000ha. That gap has widened as the fires continue to burn; as of 29 July, the cumulative burned area in France during 2026 was nearly 24,700ha above the previous record.
The fires in France follow a record-breaking June heatwave that “dried out vegetation across the region, allowing fires to spread quickly”, wrote the New York Times.
On 27 July, French president Emmanuel Macron called a “crisis cabinet meeting” in order to address the fires “ravaging several areas of south-west France”, said France 24.
More than 220,000 people have been evacuated due to the Gironde fire, west of Bordeaux, in “what may be France’s largest peacetime evacuation”, reported the Associated Press.
In the Conversation, Cunningham and two other University of Tasmania researchers write that evacuation orders “protec[t] human lives, but makes it more likely houses and other structures will burn if there’s no one to defend them”. They add:
“There is little doubt climate change has made France and Spain’s wildfires worse. They represent yet another reason to redouble our efforts to tackle climate change and stabilise our climate.”
Central Spain scorched
While Spain’s fire season has not broken records in the same way that France’s has, it is on track to be among the worst since EFFIS began reporting data in 2006.
The chart below shows the rapid increase in burned area in Spain since 8 July. The latest data from EFFIS reveal that, as of 29 July, Spain has almost matched its previous record at this point in the year. It is also nearly five times the average area burned for this time of year.
In Spain, the wildfires have been concentrated in the central part of the country, near Madrid.
BBC News reported that the fires outside the capital have burned “an area more than twice as large as the city itself”.
Nearly 90,000 people were forced from their homes in central Spain by the fires, said the Associated Press.
Pedro Sánchez, Spain’s prime minister, called the fires a “painful expression” of climate change.
Meanwhile, the UK, French and Spanish governments have issued joint statements this week in response to the fires. The UK/Spain statement begins:
“This summer’s wildfires demonstrated that climate change was now a national security emergency facing Europe and threatening our way of life.”
Related
The post Factcheck: No, Europe is not having its ‘quietest’ year for wildfires appeared first on Carbon Brief.
Factcheck: No, Europe is not having its ‘quietest’ year for wildfires
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