Research Spotlight: Global protocol provides a robust framework for calculating and reporting city-scale GHG emissions

In this latest installment of the C40 Research Spotlight series, we hear from our very own Michael Doust, Head of Measurement & Planning, on recent efforts by C40 and key research partners to help cities build credible and consistent GHG inventories – Seth Schultz, C40 Director of Research, Measurement and Planning.

A city’s ability to take effective action on climate change depends on having access to good quality data on greenhouse gas (GHG) emissions. Planning for climate action begins with developing a GHG inventory. An inventory enables cities to measure their GHG emissions, understand the contribution different activities make and determine where to best direct mitigation efforts. In addition, a city-scale GHG inventory helps cities meet legal and voluntary reporting requirements. 

However, the inventory methods that cities have used to date vary in terms of which emission sources and GHGs are included in the inventory; how emissions sources are defined and categorised; and how trans-boundary emissions (those produced by activities that cross the geographic boundary) are treated. This inconsistency makes comparisons between cities difficult, raises questions around data quality, and limits the ability to aggregate GHG emissions data.

To allow for more credible reporting, meaningful benchmarking, and better aggregation of climate data, C40 has been working with WRI and ICLEI – Local Governments for Sustainability, to develop the Global Protocol for Community-scale Greenhouse Gas Emissions (GPC), which offers a robust and clear framework that builds on existing methodologies for calculating and reporting city-scale GHG emissions.

A key feature of the GPC is that it has been designed to be consistent with the IPCC Guidelines for National Greenhouse Gas Inventories – the internationally-agreed upon methodologies to estimate and report annual GHG emissions and removals within a national territory – and allows for vertical aggregation of city emissions data. 

Alignment with the IPCC Guidelines ensures better consistency between national GHG inventories and city-wide GHG inventories; and addresses potential issues due to double-counting, omissions and incorrect attribution, leakage, etc. This is critical in facilitating cooperation between cities and national governments, which is essential for catalyzing GHG reductions. 

However, the IPCC has not yet actively promoted or considered the application of IPCC Guidelines to other areas. For this reason, the IPCC invited C40 to an expert meeting in Sofia, Bulgaria, earlier this month. The goal of the meeting was to determine how to apply IPCC Guidelines on GHG inventories to other areas, including cities, and to help the IPCC identify opportunities to enhance the utility of their guidelines. Experts from all over the world attended, representing national governments, multi national corporations, and academic institutions.

Through our contact with cities and feedback from the GPC pilot programme, we know that many cities struggle with sourcing high quality activity data, and have difficulty accurately disaggregating the data when it is available at the national scale. We also believe IPCC can offer major value to cities by providing additional guidance to national inventory compilers.

Specifically, we invited the IPCC to provide guidance, and examples of good practices, on (a) the disaggregation of activity data collected by national agencies so that it can be used in subnational inventories, and (b) aggregation of city emissions data for use in national inventories. We hope that IPCC takes these recommendations into account, which we believe will make a real difference to the quality and impact of citywide inventories.

The GPC is currently open for public comment until August 18th. To comment on the new GPC draft 2.0, please download and submit the following form by email to by August 18th.