How and when should you use proxy data?

3 October 2024

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Under CoM SSA, GHG inventories are required to align with the Global Protocol for Community-scale Greenhouse Gas Emission Inventories (GPC) and fulfil the requirements of GCoM’s Common Reporting Framework (CRF).
The process of developing GHG inventories for cities usually requires a lot of data and GHG accounting expertise.
For many cities in sub-Saharan Africa, the data required for a GHG emissions inventory either do not exist or are difficult to access, and resources within the local government to undertake GHG inventory development are limited.
Each sector and subsector (see Lesson 2.3) requires activity data to be collected, to account for the different sources of GHG emissions.
Local activity data is always the best and first choice for inventories – but is often not available or easy to access. In such cases, using proxy data is an option.
Both local and proxy data may require scaling in order to estimate the GHG emissions attributable to within the BEI boundary.

Local vs. proxy data

There are two broad data approaches that cities (and other subnational regions) can use to develop their GHG inventories:

1. Primary or local data

This approach involves collecting data directly from emission sources within the city to inform the GHG inventory. While this method provides the most accurate and specific data, it is often constrained by data availability, time, capacity, and/ or resources.

2. Proxy or downscaled data

Where locally specific or primary data are not available, proxy data can be used. This can refer to information from similar processes or activities happening in other cities, or downscaled data from national or regional level that is adjusted for the local population or economic indicators.

In practice, cities are likely to use a combination of approaches depending on data availability for each sector in the GHG inventory.
For many sub-Saharan African cities, collecting primary data for a GHG inventory faces resources and time constraints, and is not a high priority given that many of these cities are not major GHG emitters.
Often the first GHG inventory is a preliminary step to assist in the preparation and implementation of mitigation plans and actions and serves to identify areas for improvement in data collection and capacity over time.

How to scale data

Downscaling assumes the municipality’s share of GHG emissions in the region is proportional to a specified scaling factor, which is used to estimate the local government’s share of national or regional GHG emissions.
The most common scaling factors are population (the percentage of the country’s population found within a region) and GDP (the percentage of a country’s GDP generated within a region).
It is also possible to utilise more specific factors if more in depth data is available. For example, if the fraction of households that utilise firewood for cooking is known for both the country and the region, it is possible to use this as the downscaling factor for residential firewood consumption.

What are best practices for primary and secondary data collection?

Data collection is an integral part of developing and updating a GHG inventory. This includes gathering existing data, generating new data, and adapting data for inventory use.

Here are some principles of data collection that underpin good practice:

It is good practice to start data collection activities with an initial screening of available data sources.
This will be an iterative process to improve the quality of data used and should be driven by two primary considerations:
- Data should be from reliable and robust sources.
- Data should be time- and geographically specific to the inventory boundary, and technology-specific to the activity being measured.

Data can be gathered from a variety of sources:

A country’s national GHG inventory report
National and local census results
National and international reports/statistics
Ministries and government departments at the local and national level, for sector-specific information e.g. energy, transport, agriculture, etc
National utility and regulatory bodies, for sector-specific information e.g. electricity and energy
Industry and business surveys – for information about fuel consumption, electricity use, waste management, direct emissions (IPPU)
Local associations or authorities, for sector-specific information e.g, waste management authority, transport associations
Sector experts/stakeholder organisations
Household surveys – for information about household fuel consumption, waste management, etc
Universities and research institutes’ papers
Statistics agencies
Scientific and technical articles in environmental books, journals and reports.

In general, it is preferable to use local and national data over international data, and data from publicly-available, peer-reviewed and reputable sources, often available through government publications.
It may be necessary to generate new data if the required activity data does not exist or cannot be estimated from existing sources. This could involve physical measurement, sampling activities, or surveys.
- Surveys may be the best option for most emission sources, given the tailored data needs of city-wide GHG inventories, although they can be relatively expensive and time-consuming without proper guidance.
- Data collected in this manner would be referred to as primary data, while other collected data is secondary data.

CoM SSA Sustainable Energy Access and Climate Action Plan (SEACAP) course

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