Ways in Which 120 of the Globe’s Major Cities Might Reduce Transportation CO2 Emissions by 22%

Urban centers, often underestimated contributors to climate change, pose challenges in evaluating their potential emissions reductions due to their diverse nature.

A recent study, published in Nature Sustainability, analyzed transport policies across 120 cities worldwide spanning five continents. The research revealed that collectively, these cities could decrease carbon dioxide (CO2) emissions by 22% without compromising residents’ overall quality of life, as measured by a unified, monetized metric.

Various policies, including fuel taxes, public transport enhancements, and urban planning, showcased the potential to reduce transport-related CO2 by 30% or more in individual cities.

Cities and Climate Change
Despite cities accounting for 70% of global emissions, they are also pivotal in implementing local climate action. Many cities, including those in the Global Covenant of Mayors city network, aim to slash emissions by 66% by 2050.

Urban transport, representing 8% of global emissions, is a crucial sector where cities hold considerable influence.

However, evaluating the collective potential of cities to mitigate transport emissions has been complex. Each city’s unique characteristics, like urban layout and existing infrastructure, affect the impact of policies. Yet, detailed city models are challenging to generalize due to fragmented scientific literature biased toward larger cities and developed nations.

Strategies Explored
Utilizing an urban simulation model, the study estimated the collective potential of 120 cities to curb urban transport emissions. It also considered the impact of these climate actions on residents’ quality of life, encompassing housing, transport prices, local taxes, and health benefits associated with cleaner air and active transportation modes.

To calibrate the model for each city, the researchers gathered socio-economic data via web scraping from local websites and utilized transportation system data from sources like Open Street Map, Google Maps, and Baidu Maps.

The study explored four main complementary strategies: taxing polluting vehicles, promoting fuel-efficient vehicles, investing in public transport, and implementing urban planning policies to limit urban sprawl.

Comparing Local Policies
The study revealed that implementing these policies collectively could reduce overall transportation-related greenhouse gas (GHG) emissions by up to 31% across the 120 cities within 15 years.

Individually, policies could mitigate emissions by 4% to 12%, with urban transport emissions potentially being reduced by 20% to 25% through a mix of urban planning and technological solutions.

The impact of a policy varied based on the city. For instance, new public transport lines could significantly benefit most South American cities due to high population density and underdeveloped transport systems.

In Europe, taxing fuel prices proved more effective due to well-established public transport networks, while its impact in cities like Atlanta (USA) was minimal due to limited alternatives to private cars.

Combining policies, such as taxing polluting vehicles along with public transport development, showcased substantial emission reductions, particularly evident in Lille (France), where a blend of policies could lead to a nearly 24% reduction in transport-related emissions.

Assessing Quality of Life
The study evaluated policies’ impacts on residents’ quality of life, considering factors like income, transportation costs, housing prices, air quality, noise pollution, road accidents, and health benefits from active mobility.

Overall, certain policies improved air quality, reduced noise pollution and accidents, and lowered household transport budgets. However, urban planning restricting urban sprawl could increase housing prices, and setting up new public transport lines could be financially challenging.

Through a composite welfare indicator, encompassing various life quality aspects, the study showed that policy combinations can reduce emissions while maintaining or improving residents’ overall well-being across all cities examined.

Future Considerations and Climate Governance
The findings emphasize that tailored policies specific to each city’s characteristics are crucial. The study also highlights the need for local adaptation of strategies, acknowledging the diverse nature of cities.

Cities, often overlooked in global climate discussions due to their diversity, possess substantial potential in contributing to global climate goals. With increased availability of urban data, explicit modeling and evaluation of climate strategies in various cities have become feasible.

Despite current research gaps, particularly in African cities due to data challenges, ongoing trends in data accessibility might bridge these gaps, enabling comprehensive analysis in the coming years.