A lot of the research and data on greenhouse gas emissions in the past has been at the country/national or global level.
Now, more information is coming out about the significance of cities and CBD or heavily urbanized areas in the emissions picture.
This guide outlines how important it is for us to focus on cities going forward, in addition to countries and the world as a whole.
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 figures point to cities, and specifically the most well developed, urbanized and affluent cities, being a focus if we want to address climate change and global warming 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. Mitigation (reducing emissions), adaptation and sequestration are all options
- You can read more about how cities might be able to reduce emissions and address climate change in the future in this guide
- You can also read this guide about the cities with the highest greenhouse gas emissions in the world (top 500 cities in total emissions, and per capita)
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
More Information On The Carbon Footprint Of, & Greenhouse Gas Emissions From Cities
We’ve paraphrased and listed ideas from various sources below (and expanded them, or connected them to other ideas ourselves). Check out the resources list for the full resource if you’re interested.
- Economic growth and urbanization tend to lead to higher greenhouse gas emissions – richer and more developed cities tend to have higher emission footprints
- Lifestyle and level of affluence can impact GHG emission totals – the higher the affluence, the higher the GHG emissions
- Population growth can be a reason for GHG increases
- It’s expected that by 2050, 70% of the world’s population will live in cities – making them people dense areas to focus on. Urban population is expected to double by 2030 as well
- Cities consume roughly 80% of the world’s energy production and are responsible for roughly the same amount of GHG emissions
- A trend that is noticed in cities is that when a city is developing, GHGs come more from the industrial sector
- Once a city is reasonably well developed, GHGs 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 89%
- Building out (urban sprawl) and not up increases energy requirements for a city. Dense living (more people in smaller land surface areas), and building up and not out – are two ways to decrease emissions
- The energy source mix within a city plays a huge role in the GHGs emitted
- Richer cities, less dense cities, and cities that depend predominantly on coal to produce energy all emit more greenhouse gases.
- There’s total greenhouse gas emissions, and there’s per capita emissions – both can be a helpful measurement or indicator
- Per capita emissions tend to be lower in efficient and well planned cities
- To promote growth and also mitigate climate change, cities will need to shift energy sources, improve energy efficiency, and increase city density
- At some point we have to decrease consumption too – not just look to green up energy sources or move to electric vehicles (these solutions can only address some of the problem)
- Energy use in buildings and how electricity is produced are usually huge drivers of climate change
- Spatial organisation of living areas also contributes to GHGs. Single family homes, further away from services and with private cars, have higher emissions than multi unit buildings that are built up, close to public transport and services
- Cities require concentrated electricity production but with short distances to power plants so there are shorter transmission lines and less transmission losses
- Trucks, automobiles, and aircraft also need concentrated energy
- In the future, cities with more electric vehicles and desalination plants will need more energy from electricity generation
- Fossil fuels, hydroelectric and nuclear are not expected to be replaced by solar and wind in most big cities in the short to mid term future
- Less energy use/more efficient energy use, more efficient buildings and less vehicle use will be important to reducing greenhouse gas emissions
- Coal and oil are worse than gas for emissions
- City greenhouse gas emissions reflect the structure of a city, its energy sources, and its residents’ lifestyles. Resource use, water consumption, wastewater production, toxic releases, and solid waste generation are all linked among themselves and with greenhouse gas emissions as well.
- You have to define a city’s scope and geographical boundaries for GHGs when calculating the footprint
- Emissions can come from both production and consumption, inside and outside of the city
- Export and importation of GHG emissions should be accounted for
- Variables like deforestation and mining can be difficult to factor into carbon footprints
- Per capita emissions can be influenced by factors like a cold climate
- Per capita emissions can be influenced by a variety of physical, economic, and social factors specific to the unique urban life of each city.
- Infrastructure investments quickly become longterm 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 all but locked-in.
- Compact cities are more sustainable than sprawling 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
- Overall, cities should be aware of the factors they do and don’t have control over to mitigate emissions or sequester them, and to adapt to the impact of warming or cooling
- Emissions can come from within the city boundary, from off site energy production (like a power plant feeding into the grid), and from outside the city boundary (like when a city member flies out of the city)
- 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, indirect emissions and so on
- There’s a difference between production and consumption both inside and outside the city
- 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
- 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
- Be aware of exported and imported 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
- 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
- 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.
- … roughly one third of an urban resident’s footprint is determined by that city’s public transportation options and building infrastructure
- There are lists 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
- … in practice mapping footprints to local jurisdictional bounds is complex
- 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
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.