Most of the numbers and stats on greenhouse gas emissions in the past have been for the country/national, or global level.
Now, more information is coming out about the significance of cities in the emissions picture (as heavily urbanized and populated areas).
This guide outlines the basics of cities and their carbon footprints.
Summary – GHG Emissions & Carbon Footprints From Cities
The biggest and most well developed cities in the world are the source of a significant % of global greenhouse gas emissions (in total emissions, and usually per capita emissions too)
Roughly 70% of global greenhouse gas emissions come from cities (some sources say it’s higher when accounting for all production and consumption emissions)
The top 100 emitting cities in the world make up about 20% of global emissions just by themselves
Developing cities in the future are expecting to make up around 90% of the increase in carbon emissions that we will see from energy use
All these stats and trends point to cities being a focus if we want to address climate change and global warming, and specifically emissions in the future
Every city has it’s own GHG emission and carbon footprint profile though – so each city needs a different approach/strategy, and solutions
Generally, cities that are built out as opposed to up, have a lower number of people per square area of land surface (are less dense), and that use coal or fossil fuels as a main energy source, tend to emit the most emissions. Consumer cities also tend to have higher emission footprints
Mitigation (reducing emissions), adaptation and sequestration are some of the most commonly mentioned options to address climate change
Developing cities might focus on well planned out cities that are more dense in terms of people per square meter living, and planning out buildings and infrastructure like energy/electricity and transport services and systems
Some cities are locked into the current design/layout of the city or infrastructure, so will have to look at adjustable measures like changing public energy sources, increasing individual building and transport energy efficiency, and improving new building/construction design and energy efficiency. Consumer behaviors can also be adjusted
All cities could benefit from decreasing their total consumption and rate of consumption
From siteresources.worldbank.org: 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
Development in emerging cities, and modification in existing cities, should both 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.
How Much Cities Contribute To Global Greenhouse Gas Emissions
- Cities consume over two-thirds of the world’s energy and account for more than 70% of global CO2 emissions.
- Cities consume as much as 80 percent of energy production worldwide and account for a roughly equal share of global greenhouse gas emissions.
- Cities emit about 70% of the world’s greenhouse gases – but that figure only accounts for production [and not consumption]
- [just] 100 cities [in the world] drive 18% of global emissions
- Residents of just 100 cities (out of 13,000 studied in the world) account for 20 percent of humanity’s overall carbon footprint
How To Measure Emissions In Cities
You can measure either total emissions, or per capita emissions. Cumulative emissions is also an option for measurement.
You have to define a city’s scope and geographical boundaries for GHGs when calculating the footprint – otherwise it’s hard to tell where emissions come from and to compare one city to another
Emissions can come from both production and consumption, and inside and outside of the city boundary (for example, goods and materials made elsewhere, and shipped to or imported to the city). There’s also off site energy production (like a power plant feeding into the grid)
Exportation and importation of GHG emissions should be accounted for, or at least made note of as included or excluded
Emissions can be divided into the different sector allocations. Different sectors might be divided up into agriculture, forestry and land use, stationary fuel consumption, waste generated and disposed, industrial processes, in boundary transport, grid supplied energy, buildings, transport, indirect emissions, and so on
Variables like deforestation and mining can be difficult to factor into carbon footprints (as they occur so far up the supply chain)
Per capita emissions can be influenced by factors like a cold climate
Per capita emissions can also be influenced by a variety of physical, economic, and social factors specific to the unique urban life of each city.
citycarbonfootprints.info notes how mapping and measuring city footprints can be difficult:
- … in practice mapping footprints to local jurisdictional bounds is complex
Causes Of Emissions In Cities
- [Economic growth, high urban sprawl, high wealth and development, poorly planned and structured cities, more affluent lifestyles, increased population size, less density of people per square meter, building out and not up, non efficient organization of living spaces, private cars, living spaces not being located close to public transport and services, reliance on coal and carbon intensive fossil fuels for energy and electricity over cleaner less carbon intensive energy sources, long distances to power plants and longer transmission lines and more transmission losses, non concentrated electricity production (especially for vehicles and all forms of transport), more total energy use, less efficient energy use, less efficient buildings, more total vehicle use and miles travelled … all these figures can lead to increased energy requirements and higher GHG emissions in cities]
- 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
Main Industries Responsible For Emissions In Cities
It’s mainly energy and electricity production, transport and buildings.
But it’s also resource use, water consumption, wastewater production, toxic releases, and solid waste generation (siteresources.worldbank.org)
- … roughly one third of an urban resident’s footprint is determined by that city’s public transportation options and building infrastructure
- 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
- There are good reasons why most cities focus on sector-based GHG emissions. 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
Developed vs Developing Cities
There’s a difference between the profiles of developed and developing cities.
- … [in developing cities], GHGs come more from the industrial sector
- GHGs [in more developed cities] tend to come more from energy for lighting, heating, and cooling (in buildings)
- Developing countries in the future will play a major role in the increase in CO2 emissions from energy – about
Consumer, Producer, Exporter & Importer Cities
Some cities are consumer cities, some are producer cities, and different cities have a different mix of their exports vs imports (some export or import more than others)
- Consumption = production – export + import
- Imported goods that were produced outside the city tend to have the biggest footprint, followed by within the city for both consumption and production, and lastly production inside the city but exported outside
- Consumer cities are responsible for about 80% of GHG emissions, while producer cities are for 20%
- Different regions and countries in the world have different profiles for both consumption and production, and also the sectors of their city that make up their total footprint
- Be aware of exported and imported emissions
- Cities need to work with other cities that they trade with – this can address emissions that aren’t being accounted for
- Cities rely heavily on the supply of goods and services from outside their physical boundaries. The results of this study show that the GHG emissions associated with these supply chains are significant, particularly for C40 cities in Europe, North America and Oceania.
- Over 70% of consumption-based GHG emissions come from utilities and housing, capital, transportation, food supply and government services.
- 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
- 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.
- Food, clothing, electronic equipment, air travel, delivery trucks, and construction industries are examples of consumption activities
- Emissions can be outsourced from one city to another – so we have to be mindful of the complete carbon footprint picture, and not just what is produced or consumed within the city limits
- Service-based economies that consume the things that other cities make can rank better for emissions – so new carbon footprint calculations need to take into account inside and outside city emissions, and local production vs foreign production
Solutions To Decreasing Emissions In Cities
- To promote growth and also mitigate climate change, cities will need to shift energy and electricity sources, improve energy efficiency (particularly in buildings), and increase city density and become more compact and efficient (as opposed to being sprawled out)
- At some point, total consumption and consumption rate (consumption intensity) has to be decreased too – not just look to reduce emissions from energy sources or move to electric vehicles (these solutions can only address part of the problem)
Overall, cities should be aware of the factors they do and don’t have control over to mitigate emissions or sequester them.
In addition to mitigation and sequestration, cities can practice adaptation to the effects of warming or cooling.
Future Trends For Cities & Greenhouse Gas Emissions
- It’s expected that by 2050, 70% of the world’s population will live in cities
- Urban population is expected to double by 2030 as well
- In the future, cities with greater numbers of electric vehicles and desalination plants will need more energy from electricity generation
Other Notes Of Emissions & Cities
We’ve paraphrased and listed ideas from various sources below (and expanded them, or added other relevant information ourselves).
Check out the resources list for the full resource if you’re interested …
- 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
A Small Number Of Cities Make Up Majority Of Emissions
- There are lists available for the top 500 emitting cities – in total, and per capita
- Globally, carbon footprints are highly concentrated into a small number of dense, high-income cities and affluent suburbs
- 100 cities drive 18% of global emissions
- In most countries (98 of 187 assessed), the top three urban areas drive more than one-quarter of national emissions
- 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
- The bulk of a country’s consumption-related carbon emissions can be concentrated in just a few cities
- For example, 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; whereas 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.
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.