Below, we discuss carbon emissions specifically from cities, and outline the following points:
– What to know about emissions from cities
– How much of all emissions come from cities specifically
– What the top emitting cities in the world are
– How cities might address emissions
Summary – Carbon Emissions From Cities
Potentially Important Points About Emissions From Cities From The Data Below
Some conclusions we might draw from the data below might be:
– Cities are responsible for most of the world’s energy consumption, and also most of the world’s emissions
– Just 100 cities (of all the world’s cities) are responsible for a large % of the world emissions
Some of these cities might be some of the largest and most well developed cities
– In addition to wealthy/high income cities, densely populated cities can drive high carbon footprints amongst the top 200 cities
– ‘Consumer’ cities are responsible for far more emissions than ‘producer’ cities
– ‘Consumer’ cities that import a lot of their goods may ‘outsource’ their production related emissions to exporter cities
– In the future, most of the world’s population is projected to live in cities
– In the future, developing cities specifically (as opposed to developed cities) might make up the vast majority of emissions increased from energy use
– Cities specifically might be a key focus for addressing emissions in the future
– There might be a range of things cities can do to reduce their emissions, but, there are also cities that have already ‘peaked’ their emissions using various strategies and methods
– Ultimately, each city has their own carbon footprint profile (in terms of their total emissions, where their emissions comes from in terms of sectors/industries/activities, whether they are a consumer or producer city, whether they mainly export or import, and so on), and therefore needs their own specific strategy to address emissions (and their overall sustainability)
Points About Emissions From Cities Outlined Below
The points we outline below are:
– What % of all emissions come from cities specifically
– Considerations when measuring and assessing emissions from cities
– Main causes of emissions from cities
– Which industries are responsible for majority of emissions from cities
– Differences in emissions from developed vs developing cities
– Considering consumption, production, exports, and imports for cities
– A small number of cities make up majority of emissions from cities
– Which cities are the top emitting cities in the world – both in total emissions, and per capita emissions
– Potential future trends for cities and emissions
– How cities might reduce emissions (potential solutions)
– Examples (case studies) of cities that have already peaked/reduced emissions
– Potential limitations in addressing emissions in cities
– Tracking how cities are addressing emissions
What % Of All Emissions Come From Cities?
From the data below, cities might:
– Consume 66% to 80% of all the world’s energy
– And, emit 70% to 80% of all the world’s emissions
Additionally, there might be just 100 cities (out of all the world’s cities) that are responsible for 18% to 20% of all of the world’s emissions.
These numbers might only include consumption related emissions though, and not production related emissions.
So, the numbers might be higher when accounting for production related emissions too.
It might be accurate to say that cities specifically make up a very large % of the world’s emissions.
With cities being heavily urbanized and heavily populated areas, this might make logical sense.
We’ve previously written about whether we should focus on addressing climate change at the city level, or the country level.
The data here might suggest that cities should be the priority.
What % Of Emissions All Cities Are Responsible For
Cities consume over two-thirds of the world’s energy and account for more than 70% of global CO2 emissions (c40.org)
Cities consume as much as 80 percent of energy production worldwide and account for a roughly equal share of global greenhouse gas emissions (siteresources.worldbank.org)
Cities emit about 70% of the world’s greenhouse gases – but that figure only accounts for production [and not consumption] (news.nationalgeographic.com)
Just 100 Cities Responsible For A Significant % Of All Global Emissions
[Just] 100 cities [in the world] drive 18% of global emissions (citycarbonfootprints.info)
Residents of just 100 cities (out of 13,000 studied in the world) account for 20 percent of humanity’s overall carbon footprint (scientificamerican.com)
Considerations When Measuring & Assessing Emissions From Cities
Main Ways To Measure Emissions From Cities
Two key measurements might be:
– Total emissions
– Per capita emissions
Another less common measurement might be cumulative emissions i.e. net emissions over time.
Other Considerations When Properly Calculating/Assessing A City’s Emissions
Other considerations to accurately calculate/assess a city’s emissions (that should be noted in the report/assessment), might include:
– Defining the scope and geographical boundaries for emissions of a city
Without doing this, it’s difficult to tell what a footprint includes (and doesn’t include), where emissions come from (inside or outside the city), and to compare one city’s footprint to another’s
– Delineating between, and properly attributing emissions from inside and also outside of the city boundary
For example, electricity might be produced outside the city boundary, and transported to the city for consumption
A power plant feeding the grid that the city uses is an example of this
– Delineating between, and properly attributing production vs consumption related emissions
For example, a car might be produced outside the city’s boundary, but bought and used inside the city’s boundary
– Delineating between, and properly attributing export and import related emissions
Cities may export and import products and services between one another
The emissions from these exports and imports need to be properly attributed
– Properly attributing emissions to the different industries and sectors within a city
Emissions can be divided into the different sectors and industries within the city
Different sectors might be divided up into agriculture, forestry and land use, stationary fuel consumption, waste generated and disposed, industrial processes, in boundary transport, inter boundary transport, grid supplied energy, buildings, indirect emissions, and others
– Taking into account indirect emissions up and down the supply/production chain
Such as indirect emissions for mining and sourcing of resources and materials, processing, manufacturing, transport/freight, consumption, waste management, and others
Although, variables like deforestation and mining can be difficult to factor into carbon footprints (as they occur so far up the supply chain)
– Taking into account factors and variables specific to an individual city
For example, per capita emissions can be influenced by factors like a cold climate, where that city might have to use more energy and heating than another city in a more moderate climate
Other physical, economic, and social factors can also impact the footprint of individual cities
– Inclusions and exclusions in each individual carbon footprint report for each individual city
Always make sure to look at what data has been included and excluded in the report, and how the calculations have been done.
This can help in understanding what the footprint represents, and help with comparing footprints to one another.
One key example of this might be the lifecycle stages that have been included in the carbon footprint.
Other examples might included where the boundary has been drawn for the city, the export and import emissions that have been included and excluded, and so on.
Complexity & Difficulty Of Calculating A City’s Carbon Footprint
Ultimately, it might be difficult and time consuming/resource intensive to accurately map/measure a city’s carbon footprint for various reasons.
… in practice mapping footprints to local jurisdictional bounds is complex
Carbon Footprints Are Not Definitive
We’ve previously mentioned that carbon footprints are a general guide or general tool only, and are not definitive.
There’s many variables and factors that can contribute to each footprint, and there can be limitations and difficulties/complexities in calculating a footprint.
Main Causes Of Emissions In Cities
Paraphrased and summarised from siteresources.worldbank.org, some of the major causes of emissions in cities might be:
Larger population sizes, or general population growth
Higher levels of wealth and development
More affluent lifestyles of the people living in the city
More urban sprawl, and building out instead of up
Cities that are planned and structured in a way not conducive to efficient energy use, or lower emissions
Living spaces and working spaces (like work building, and workplaces) that aren’t efficient (especially from an energy use perspective)
Living spaces not being located close to public transport and other services
More private vehicles being in use on the road, and more total miles/kilometres being travelled
Higher rates of using private passenger cars (instead of other modes of transport)
Higher total energy use, and lower energy efficiency
Reliance on coal, fossil fuels, and carbon intensive fossil fuels for energy and electricity (over less carbon intensive energy sources)
Longer distances between power plants, and where electricity is delivered to/used in cities. Longer transmission lines may lead to more transmission losses for example
Non concentrated electricity production (especially for vehicles and all forms of transport)
Additionally, siteresources.worldbank.org notes that ‘… the variation in per capita emissions in cities results from differences in wealth, sectoral specialization, energy sources, the general climate, and the structural efficiency of the urban form, which includes buildings and transport infrastructure.’
Read the siteresources.worldbank.org report for the more details on these causes
It’s worth mentioning that there’s a different between the causes of total emissions, and per capita emissions. For example:
Lower densities of people per square meter in a city might lead to higher per capita emissions
But, a large total population size can lead to higher total emissions in some instances
Which Industries Are Responsible For Majority Of Emissions In Cities?
Transport, building infrastructure, energy and electricity production, and a range of other industries might be some of the major emitting industries in cities.
However, the exact industries might vary city to city.
Industries/Sectors Responsible For The Most Emissions Within Cities
… roughly one third of an urban resident’s footprint is determined by that city’s public transportation options and building infrastructure (scientificamerican.com)
Over 70% of consumption-based GHG emissions come from utilities and housing, capital, transportation, food supply and government services (c40.org)
[Emissions come mainly from] energy and electricity production, transport and buildings.
But … also resource use, water consumption, wastewater production, toxic releases, and solid waste generation
Capital and buildings, utilities and housing, food, beverage and tobacco, public transport, private transport and government tend to have the biggest carbon footprints
This is followed by clothing, furnishing and household equipment, restaurants, hotels, recreation and culture, communications, education and health, miscellaneous goods and services, and other sources of emissions
Differences In Emissions From Developed vs Developing Cities
Developed and developing cities may differ in their emissions profiles, and also in terms of future projected emissions.
Emissions might come from different industries/sectors in developing and developed cities – in part due to the stage of development their economies are at.
Additionally, developing cities might be projected to be responsible for a much higher % of future emissions than developed cities.
Where Emissions Come From In Developing Cities
… [in developing cities], GHGs come more from the industrial sector (siteresources.worldbank.org)
Where Emissions Come From In Developed Cities
GHGs [in more developed cities] tend to come more from energy for lighting, heating, and cooling (in buildings) (siteresources.worldbank.org)
Emissions From Developing Cities In The Future
Developing countries in the future will play a major role in the increase in CO2 emissions from energy … (siteresources.worldbank.org)
Considering Consumption, Production, Exports & Imports For Cities
There’s a difference between consumption related emissions, and production related emissions.
Some cities might primarily be consumer cities (i.e. they consume more than they produce), and some cities might primarily be producer cities (they produce more than they consume).
Consumer cities might be responsible for a far higher % of emissions than producer cities.
Additionally, different cities have a different balance of what % of goods they import, and also export.
It’s possible some cities may ‘outsource’ a % of the emissions they are responsible for by consuming goods produced elsewhere and imported into the city, but not being held responsible for those emissions.
Including all production and consumption related emissions, and properly attributing export and import related emissions, might help make city related carbon footprints more accurate and reliable.
Relationship Between Consumption, Production, Exports & Imports
Consumption = production – export + import (c40.org)
What Goods Have The Highest Carbon Footprint
Imported goods that were produced outside the city tend to have the biggest footprint, followed by [goods that are both produced and consumed within the city], and lastly [goods produced inside the city but consumed outside of it] (c40.org)
Accounting For Both Production & Consumption Related Emissions For Cities
Carbon footprints of cities are higher when production and consumption emissions are counted inside and outside the city, and not just for products produced or used inside the city (news.nationalgeographic.com)
Which Cities Have A Larger Emissions Footprint – Consumer Cities Or Producer Cities?
Consumer cities are responsible for about 80% of GHG emissions, while producer cities are for 20% (c40.org)
Wealthy “consumer cities” such as London, Paris, New York, Toronto, or Sydney that no longer have large industrial sectors have significantly reduced their local emissions.
However, when the emissions associated with their consumption of goods and services are included, these cities’ emissions have grown substantially and are among the highest in the world on a per person basis
Meanwhile, “producer” cities in India, Pakistan, or Bangladesh generate lots of industrial pollution and carbon emissions in the manufacture of products that will be sold and consumed in Europe and North America.
Examples Of Consumption Activities
Food, clothing, electronic equipment, air travel, delivery trucks, and construction industries are examples of consumption activities (news.nationalgeographic.com)
Imported & Exported Emissions
Cities rely heavily on the supply of goods and services from outside their physical boundaries
[Cities trade with each other with exports and imports, and cities need to attribute emissions related to these exports and imports properly, along with being aware of trade emissions that aren’t being accounted for]
The results of [a] study show that the GHG emissions associated with these supply chains are significant, particularly for C40 cities in Europe, North America and Oceania.
Emissions can be outsourced from one city to another [when a consumer city isn’t assigned the emissions for the goods they consume, and they are instead assigned to producer cities] … [and …] Service-based economies that consume the things that other cities make can rank better for emissions …
… so we have to be mindful of the complete carbon footprint picture, and not just what is produced or consumed within the city limits [. Additionally,] new carbon footprint calculations need to take into account inside and outside city emissions, and local production vs foreign production
A Small Number Of Cities Might Be Responsible For A Significant % Of Emissions
A small number of cities might be responsible for a significant % of some countries’ consumption related emissions
And, on a global level, a minority of large cities might be responsible for a notable % of the world’s emissions. These cities might generally be densely populated, or wealthy/high income cities.
A Few Cities Make Up A Significant % Of A Country’s Consumption Related Emissions
The bulk of a country’s consumption-related carbon emissions can be concentrated in just a few cities (scientificamerican.com)
In most countries (98 of 187 assessed), the top three urban areas drive more than one-quarter of national emissions (citycarbonfootprints.info)
… residents of South Korea’s capital, Seoul, account for about 45 percent of that nation’s overall carbon emissions
… in the U.K., London, Manchester and Birmingham combined contribute more than 20 percent of national output
… in the U.S. people living in Chicago, New York and Los Angeles combine to account for nearly 10 percent of the country’s overall footprint.
A Minority Of Cities Make Up A Significant % Of Global Emissions
100 cities drive 18% of global emissions … [and they tend to be] dense, high-income cities and affluent suburbs
Where The Top Emitting Cities Are Found Globally
41 of the top 200 cities are in countries where total and per capita emissions are low e.g. Dhaka, Cairo, Lima.
In these cities population and affluence combine to drive footprints at a similar scale as the highest income cities
Top Emitting Cities In The World
The top emitting cities in the world can be measured both in total emissions, and per capita emissions
Cities That Emit The Most Greenhouse Gases & Carbon Dioxide (In Total)
[The top 30 cities with the largest carbon footprints (in total carbon dioxide emissions) are:]
Hong Kong SAR
Country Of Singapore
View the full list of the top 500 cities at citycarbonfootprints.info
Cities That Emit The Most Greenhouse Gases & Carbon Dioxide (Per Person/Per Capita)
[The top 30 cities with the largest carbon footprints per capita/person are:]
Hong Kong SAR
Mohammed Bin Zayed City
Country of Singapore
View the full list of the top 500 cities at citycarbonfootprints.info
Potential Future Trends For Cities & Emissions
Through to at least 2030 and 2050, the population of the world’s cities and urban areas is expected to grow
These cities will be an important focus, as well as those that use more electricity for EVs and desalination
Cities Having Majority Of The World’s Population In The Future
It’s expected that by 2050, 70% of the world’s population will live in cities [and] Urban population is expected to double by 2030 as well
The Role Of Electric Vehicles, & Desalination
In the future, cities with greater numbers of electric vehicles and desalination plants will need more energy from electricity generation
How Cities Might Reduce Emissions (Potential Solutions)
Below are some potential solutions that contain some of our own potential solutions, but also some summarised and paraphrased solutions from siteresources.worldbank.org, citycarbonfootprints.info, and c40.org/networks.
Consider the top 100 to 500 cities that are responsible for the most total emissions, and per capita emissions globally
Be aware that mitigation (reducing emissions), adaptation and sequestration are some of the most commonly mentioned options to address climate change
Be aware of the factors that can and can’t be changed within a city e.g. some city infrastructure might be hard or impossible to change in cities where it’s already in place.
Be aware how city planning impacts energy efficiency e.g. living space being close to public transport and services, or, having shorter transmission lines for power
Be aware of the individual sectors and industries responsible for the most emissions within a city, such as electricity generation, transport, buildings and infrastructure, food waste and loss, waste management, and others
Be aware of how population growth impacts total emissions
Consider how population density impacts per capita emissions
Consider how high consumption, resource intensive lifestyles impact emissions, especially in wealthier or more developed cities
Consider less carbon intensive energy sources for electricity
Consider less carbon intensive fuels for transport
scientificamerican.com mentions: ‘If cities would switch to a more efficient energy source or make their public buses electric … they could slash their emissions by at least 25 percent’
Consider how total vehicles being used, and total passenger miles/kilometres travelled annually impacts emissions
Consider how alternate fuel vehicles, mass transit (like trains, buses, etc), and walking and biking can impact emissions
Improve energy efficiency (in homes, buildings, etc. – especially for heating, cooling, refrigeration and lighting)
Consider how new builds, and retrofitting of existing builds can be more energy efficient
Consider the impact of urban sprawl and per person efficiency on emissions
Consider how food, waste and water can be targeted, by reducing food waste, managing general waste better, and using water more efficiently
Consider adding vegetation and greenery to cities and around cities (on rooftops, on facades, and on sequestration towers)
Narrow down the scope of the footprint – what emissions are counted, where they are coming from, the boundaries of the city, how far up and down the supply chain you are targeting, and so on
More Specific Solutions
– Have a custom strategy and plan for each individual city based on the emission profile of the individual city
– Consider both total emissions, and emissions per capita of a city
There’s also another measurement not used as often – the carbon intensity of an activity
– Consider the lifecycle of products and materials for a full carbon footprint
Understand how far up the production and supply chain you are counting emissions – indirect supply, transport, delivery and manufacturing chain can all be included or excluded.
– Get an accurate picture of the geographic boundaries of a city for an idea of where emissions are happening
Understand where emissions take places, and who is responsible for them.
Variables like deforestation and mining can be difficult to factor into carbon footprints for cities because of how disconnected they can be from final consumption
– Consider the sectors that make up the biggest % share of emissions in the city – focus on the sectors responsible for most emissions
– Understand that outer city areas, and inner city areas may have different emission rates.
– Understand the difference between the profile of a developed city, and a developing city
– Understand the difference in profile of a consumer city, a producer city, an exporter city, and an importer city
– Focus on consumer cities which tend to have higher emissions footprints
– Accept that some cities (due to layout, design and geography) are locked into some limitations
– Consider how addressing emissions can fit into an overall sustainability strategy for a city
– Consider that cities might have more direct influence over sector based emissions compared to indirect energy usage further up the supply chain
– Consider the impact that new technology like desalination plants and electric vehicles will have on energy use
These types of technology may use more energy
– Social norms and culture within cities can impact emissions
If more people buy into the concept of sustainable cities, emissions might be lower based on behavior and other factors
– Understand that factors like climate, geography, economic and sectoral profile, and other variables can impact individual cities
Focussing On Industry Or Sector Based Emissions In Cities
Industry and sector based emissions might be easier to address for cities
[One of the main] reasons why most cities focus on sector-based GHG emissions [is that they] occur from sources over which cities often have more direct influence; are easier and more reliable to estimate and monitor
… cities may not have much direct influence over the carbon intensity of power used in the manufacturing process of an imported product, or whether that product is transported by train or truck, as end users and centres of innovation and change
Focussing On Reducing Total Consumption, & Consumption Rate
Apart the solutions mentioned above, cutting total consumption and the consumption rate in cities might be important to consider
[Additionally] At some point, total consumption and consumption rate (consumption intensity) has to be decreased too [instead of focussing on solution like electric vehicles and carbon efficient energy sources]
Focussing On Sustainability Issues Outside Of Just Emissions
Outside of just the carbon footprint of a city, development in emerging cities, and modification in existing cities, might focus on sustainability principles that address a range of sustainability issues and not just greenhouse emissions e.g. supply of freshwater, air quality, land degradation, over population, and so on.
Examples (Case Studies) Of Cities That Have Already Peaked/Reduced Emissions
You can find examples of cities that have already got results or done something to reduce greenhouse gas emissions at c40.org
They mention the following about cities currently attempting to reduce emissions:
27 of the world’s … cities, representing 54 million urban citizens and $6 trillion in GDP have peaked their greenhouse gas emissions [and] … the cities have seen emissions fall over a 5 year period, and are now at least 10% lower than their peak.
The cities are: Barcelona, Basel, Berlin, Boston, Chicago, Copenhagen, Heidelberg, London, Los Angeles, Madrid, Melbourne, Milan, Montréal, New Orleans, New York City, Oslo, Paris, Philadelphia, Portland, Rome, San Francisco, Stockholm, Sydney, Toronto, Vancouver, Warsaw, Washington D.C.
Some of the ways they achieved this were:
Decarbonisation of the electricity grid
Optimizing energy use in buildings
Providing cleaner, affordable alternatives to private cars
Reducing waste and increasing recycling rates
Investing in sustainable infrastructure and policies
Collaborating with national and regional governments and businesses operating within cities, as well as citizens, to deliver the collective action needed to cut emissions
Potential Limitations In Addressing Emissions In Cities
There might be some things that cities can’t change, or that they find difficult to change when they are trying to address emissions.
For example, existing city infrastructure and the existing design/layout of a city may be ‘set’ or ‘locked in’ to a certain extent, and may only be able to be changed in a certain way, or sometimes, not changed at all.
These things are examples of potential limitations when implementing potential solutions to address emissions.
Infrastructure investments quickly become long term sunk costs.
The transportation system that a city develops largely defines the final shape of the city, as influenced by local geography.
Roads and public transit lines are the bones of a city, with water, wastewater and power services fleshing out the city.
Once buildings grow around transportation and service nodes, they are … locked-in
Tracking How Cities Are Addressing Emissions & General Sustainability
c40.org tracks how some cities are progressing in terms of addressing greenhouse gas emissions, & general sustainability
The Carbon Footprint Of A City vs Other Sustainability Indicators
It’s worth noting that the carbon footprint of a city is only one of a range of factors that contributes to how sustainable or green a city is.
6. Moran, D., Kanemoto K; Jiborn, M., Wood, R., Többen, J., and Seto, K.C. (2018) Carbon footprints of 13,000 cities. Environmental Research Letters DOI: 10.1088/1748-9326/aac72a.
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