Metropolitan areas play an important role in the fight against climate change. While cities only take up 3% of the land on Earth, they account for two-thirds of global energy demand and 70% of CO2 emissions. [1] However, there are steps being taken in the right direction: many mega-cities such as Rio de Janeiro, New York, Paris, Oslo, Mexico City, Melbourne, London, Milan, Cape Town, Buenos Aires, Caracas, Copenhagen, and Vancouver have committed to becoming carbon neutral by 2050.[2] At the same time, small and medium-sized cities are also pursuing the same goal in the framework of the Covenant of Mayors and are planning to achieve this through the adoption of Sustainable Energy and Climate Action Plans (SECAPs).

How can cities lower their carbon emissions? While there are many options, two central axes involve transportation and the building sector. By opting for lower-emission vehicles or switching to cycling altogether, the carbon footprint of cities can substantially be reduced.[3]  At the same time, the building sector requires a lot of energy for construction, maintenance and operation. According to 2015 estimates, 38% of global energy-related CO2 emissions came from buildings.[4] This can be remedied by making buildings more energy and material efficient and less reliant on fossil fuels for construction, heating, cooling and powering.

But what exactly is a carbon footprint and how is it measured? The European Court of Auditors refers to it as “the overall quantity of CO2 and other greenhouse gas emissions caused directly and indirectly by a product or an activity or associated with the activities of an individual or an organisation.”[5] It is measured by adding up all the emissions resulting from every stage of a product or a service’s lifetime.[6] The widely used GHG Protocol identifies three main categories of emission sources (‘scopes’), which make it possible to further track the types of emissions being generated.

Scope 1 refers to direct emissions produced by a city through the use of oil, gas and other fossil fuels in combustion processes (e.g., heating boilers) for instance. In contrast, scope 2 covers the emissions it causes indirectly by purchasing electricity and/or district heating and cooling for its buildings for example. These are then emissions being released on its behalf. Finally, scope 3 emissions focus on all the emissions the city is indirectly responsible for both upstream and downstream of its value chain. These tend to relate to emissions generated by industry, households, public transport and mobility and must be analysed both upstream and downstream.

For companies and cities trying to improve their carbon footprint, scope 3 emissions are very important as these account for about 70% of all emissions. [7] That means that both small, medium-sized and large cities will have to start scrutinizing all three scopes and make the necessary data available to track their progress. Indeed, many cities have set themselves the goal of becoming carbon neutral, which not only requires the tracking of scope 3 emissions but also entails far-reaching carbon sequestration measures. While these should help reduce the city’s carbon footprint and support the fight against climate change, the real emphasis must lie on the reduction of emissions.

  Source: European Court of Auditors

[1] Cities must reduce their carbon footprint | World Economic Forum (

[2] How cities are going carbon neutral – BBC Future

[3] How cities are going carbon neutral – BBC Future

[4] How cities are going carbon neutral – BBC Future

[5] How do the EU institutions and bodies calculate, reduce and offset their greenhouse gas emissions? (

[6] Carbon Footprint Factsheet | Center for Sustainable Systems (

[7] What are scope 1, 2 and 3 emissions? | Deloitte UK