Scotland's Carbon Footprint 1998-2018

How has Scotland's Carbon Footprint been calculated?

Step 1. Develop an Input-output (IO) model

Input-output models are used by environmental researchers to make the link between the environmental impacts associated with production techniques and the consumption of products. The Leontief Input-Output model is constructed from economic data and shows the interrelationships between the industries that produce goods (outputs) and those that consume goods (inputs) from other industries in the process of making their own product. Further information on the Input-Output (IO) model and a User Guide can be found on the Input-Output webpages of the Scottish Government website.

Within the IO model, greenhouse gas emissions are reallocated from the industries that produce them to the final consumption activities that are assumed to ultimately have been their drivers. The emissions of each industry required in the production of a product are reallocated to the demand of this product, rather than the supply. In other words, we can show the greenhouse gas emissions associated with consumption. Adding an exogenous environmental variable to an IO framework produces an Environmentally Extended Input-Output model (EEIOM). The Greenhouse Gas model, also known as a Carbon Footprint, is one such example of a model.

Step 2. Develop a Multi-Regional Input-Output (MRIO) model

The University of Leeds has been contracted by the Scottish Government to provide estimates of Scotland's carbon footprint. The project updates previous work carried out by the Stockholm Environment Institute (SEI) published by the Scottish Government in 2009. A Multi-Regional Input-Output (MRIO) model allows the greenhouse gas emissions embodied to be estimated within traded goods and services. An MRIO model is used to link the flows of goods and services described in monetary terms, with the greenhouse gas emissions generated in the process of production.

Data relating to pre-1998 were assessed as being less reliable and consequently the time series used for this release is limited to 1998-2018. The system assumes a linear relationship between greenhouse gas emissions and changes in final demand, meaning that if all final demand doubled for a particular commodity, emissions would double too.

Step 3. Develop UK Based MRIO Model

In 2012, researchers from the Sustainable Research Institute at the University of Leeds constructed a UK MRIO model for DEFRA. The model uses the Office for National Statistics UK supply and use tables in 106 sectors and data from the Eora MRIO to trace the trade with a number of identified regions in the rest of the World to complete the MRIO. In the latest release, the number of regions identified has been substantially increased over previous releases.

Step 4. Develop the Scottish Consumption Based Account (the Scottish Carbon Footprint)

To calculate a consumption based account for Scotland, we use the UK MRIO model and replace the UK final demand with the Scottish final demand taken from the Scottish Input-Output tables.

The consumption based account also contains data on direct greenhouse gas emissions from households and is broken down into those from home heating and travel. Data from the UK Environmental Accounts produced by the Office for National Statistics at a UK level have been used to calculate residential heating and private motoring consumption based emissions. Scotland's share of these UK greenhouse gas emissions are calculated using data from the National Atmospheric Emissions Inventory website.