London - Assessment of Greenhouse Gas Emissions

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The ability of city leaders and other stakeholders to take effective action on climate change depends on access to good quality data and measurement of GHG emissions. London has produced a GHG emissions inventory annually since 2004. However, to further advance climate action in London, two additional steps were identified. London’s GHG inventory needs to provide an indication of a greater breadth of emission sources, both direct and indirect, to more accurately reflect the reach of its potential climate impact, and the data needs to be comparable with that of other cities to allow for meaningful benchmarking.


In 2013, the Greater London Authority (GLA) responded to this challenge by launching PAS2070, a specification providing a robust and transparent method for consistent, comparable and relevant quantification, attribution and reporting of direct and indirect city-scale GHG emissions, following internationally recognized GHG accounting and reporting principles.

The effort builds on the C40 and partners’ Global Protocol for Community-scale GHG emissions (GPC), for which London was also a pilot city, to include a wider range of indirect emissions and a separate consumption-based methodology. It specifies requirements for identifying the assessment boundaries; the sources of GHG emissions to be included; the data requirements for carrying out the analysis; and the calculation of the results to develop a city-scale GHG inventory.

This project is innovative in several other ways, including:

  • It expands the scope of what is traditionally measured by cities in GHG inventories to consider consumption-based emissions as well.
  • The results are shared publicly through London’s open data platform and presented as a published case study.
  • The assessment is verified by an independent third party.

In 2014, the GLA completed and verified their assessment using the PAS2070 and aligning to the GPC, showing London’s impact on climate change from both a production and consumption perspective. London’s current GHG inventory – limited to energy use in buildings and transport – estimates annual emissions of 44 million tons CO2 for 2010. The consumption-based approach set out in PAS2070, on the other hand, indicates that London’s consumption could produce annual emissions of 114 million tons CO2e for 2010. The assessment shows that activities previously not captured in London’s GHG assessment, such as aviation, food and other goods and services, give rise to the production of significant GHG emissions beyond its boundaries.

Projected Outcomes

The project will allow London to consider a greater range of mitigation actions, and prioritize more effectively based on comprehensive emissions data and experience from other cities. The main benefits will be realized in the design and inclusion of future climate change mitigation measures in the Mayor’s strategies, considering both production and consumption-based emission sources. It is also anticipated that London’s assessment will be a standard that other cities can follow, and that will focus attention on the carbon impact of key supply chains supporting cities.