New C40 research released at the Cities IPCC Cities and Climate Change Science Conference takes a different look at city emissions, based on the goods and services consumed by urban citizens, including food, clothing, electronics, construction and air travel.

It reveals C40 cities have a 60% larger carbon footprint than previously estimated, giving mayors a greater opportunity to deliver on Paris Agreement goals.

Download the full report here


Edmonton, Canada (06 March 2018) — Greenhouse gas (GHG) emissions generated by the world’s greatest cities are as much as 60% higher than currently estimated, when also accounting for the impact of trade in goods and services between cities and the rest of the world.  New analysis by C40 Cities, the University of Leeds, University of New South Wales, and Arup examined the GHG emissions associated with goods and services consumed by residents of 79 C40 cities, including food, clothing, electronic equipment, air travel, delivery trucks and construction industries.

The research found that almost two-thirds of these consumption-based emissions are generated in the supply chains of goods and services imported from regions outside cities. Whilst a city government may have little direct control over these emissions sources, they are released because of a city’s demand for goods and services for its citizens. This “sphere of impact” creates opportunities for mayors, city officials and urban citizens committed to urgent climate action to influence a higher percentage of the world’s GHG emissions.

“By revealing the scale of emissions generated by the urban consumption of a range of everyday goods and services, including the food on supermarket shelves, air travel or online shopping and home delivery, consumers and policy makers can make better informed decisions about the impact their choices are having,” said Mark Watts, Executive Director, C40 Cities. “Mayors need accurate data and scientific advice in order to make good policy decisions. This new research will help city policy makers to better understand the true impact of their city on global climate change, and so play an ever bigger leadership role in delivering climate action.”

The results of this study show that consumption-based GHG emissions of C40 cities are often significantly larger than the those calculated under alternative methods that focus primarily on GHG emissions taking place within the city boundary, such as the Global Protocol for Community-scale Greenhouse Gas Emissions Inventory (GPC) BASIC level reporting standard. This is particularly true for cities in Europe, North America and Oceania, reflecting both the higher levels of consumption in those cities, and the global nature of supply chains of the goods and services used by their citizens. 15 cities, mostly in Europe and North America, have consumption-based GHG emissions at least three times the size of their emissions calculated using the GPC.

“If you look at the emissions from ‘consumer’ cities like London, Paris or New York, they have very little from industry, because their economies and workforces are no longer reliant on manufacturing and factories,” said Mark Watts. “Yet ‘producer’ cities in India, Pakistan or Bangladesh, for example, are generating a lot of industrial pollution in the manufacture of products that will be sold and consumed in Europe and North America. By examining consumption-based GHG emissions alongside existing inventories, policy makers can get a more complete picture of the opportunities to reduce global GHG emissions and deliver on the goals of the Paris Agreement.”

The results of the study are presented at global and regional level, categorised by sector of the economy.  For cities in Africa, South & West Asia and Latin America, more than one fifth of their consumption based emissions are generated in food production, compared to well below 10% in North American or East Asian cities. In European cities, for example, expenditure on restaurants, hotels, recreation and culture account for as much as 8% of consumption based emissions. Public transport, which includes rail, shipping and aviation, contributes on average 10% to consumption-based GHG emissions across C40 cities.

To date, mayors of 35 C40 cities have publically committed to develop and begin implementing ambitious climate action plans by 2020 that go beyond national commitments, in order to achieve the highest goals of the Paris Agreement at the local level.

The research was presented today in Edmonton, Canada where the CitiesIPCC Cities and Climate Change Science Conference is taking place.


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Total consumption-based emissions of the 79 C40 cities included in the study are 3.5 Gt CO2e. This represents a 60% increase on the 2.2 GtCO2e emissions estimated for the same cities using the GPC BASIC standard.

A city consumption-based GHG inventory can be defined as the emissions arising within a city’s boundaries, minus those emissions associated with the production of goods and services exported to meet demand outside the city, plus emissions arising in supply chains for goods and services produced outside the city but imported for consumption by its residents: Consumption = Production – Exports + Imports

Data is not provided at a city-level as the purpose here is not to focus on individual city emission profiles. Please note, due to the many assumptions made in the methodology, the results are only able to provide an indicative approximation of the GHG emissions associated with a city’s consumption activities

It should be noted that different reference years were used in this work (2011) and the GPC inventories (various between 2011 and 2015). Hence, the comparison of the emissions reported should be considered as an indicative difference in emissions, rather than as an exact number.

The following C40 cities have publically committed to develop and begin implementing ambitious climate action plans that meet the highest aspirations of the Paris Agreement by 2020: Accra, Addis Ababa, Amman, Austin, Barcelona, Boston, Buenos Aires, Cape Town, Caracas, Copenhagen, Dubai, Durban, Hong Kong, Johannesburg, Lagos, London, Los Angeles, Medellin, Melbourne, Mexico City, Milan, New York City, Oslo, Paris, Philadelphia, Portland, Quito, Rio de Janeiro, Salvador, Santiago, Stockholm, Sydney, Tshwane, Vancouver, Washington, D.C.


About the C40 Cities Climate Leadership Group

C40 Cities connects more than 90 of the world’s greatest cities, representing 650+ million people and one quarter of the global economy. Created and led by cities, C40 is focused on tackling climate change and driving urban action that reduces greenhouse gas emissions and climate risks, while increasing the health, wellbeing and economic opportunities of urban citizens. The current chair of the C40 is Mayor of Paris Anne Hidalgo; and three-term Mayor of New York City Michael R. Bloomberg serves as President of the Board. C40’s work is made possible by our three strategic funders: Bloomberg Philanthropies, Children’s Investment Fund Foundation (CIFF), and Realdania. To learn more about the work of C40 and our cities, please visit, follow us on Twitter @c40cities or Instagram @c40cities and like us on Facebook at

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