Background to the statistics
The University of Leeds has been contracted for five years 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. It uses a multi-region input-output (MRIO) model, to link the flows of goods and services described in monetary terms, with the emissions generated in the process of production. The latest estimates benefit from recent modelling developments at the University of Sydney where data from their "Eora" model feeds directly into the Scottish model. In brief, this is a sophisticated computer model that can assimilate data on emissions and product flows from different countries and years in different classifications and valuations, dealing with the data gaps and reconciling inconsistencies. Data relating to pre-1998 was assessed as being less reliable and consequently the time series used for this release is limited to 1998-2010.
The methods and data sources used in this research remain consistent with those used in the previously published results that are documented in Wiedmann et al (2008i) with the differences relating to country coverage and sector breakdown. Due to a change in the Standard Industrial Classification (SIC) used in some of the source data, additional effort has been needed to re-allocate estimates from the more recent classification covering 110 sectors to the previous coverage of 123 sectors.
Revisions to the data since previous release
Provisional results for 1998-2009 were published on the Scottish Government website as "data being developed" (Scottish Government, 2012). Since then, the model has been further refined by the University of Leeds. It now separates imports into three regions: China, the EU and the Rest of the World and provides consistent time series over the whole period - previously results prior to 2004 did not reflect the technology of every country along the supply chain. These refinements are able to capture emissions that occurred in these regions across all stages of the supply chain. Whilst the trends remain consistent with previous estimates, the recent refinements have resulted in GHG estimates that are generally higher than previously estimated. In addition the latest figures make use of updated Scottish Input-Output tables which use the 2007 Standard Industrial Classification (SIC). A methodological note is available on request further detailing the revisions.
Greenhouse gas emissions uncertainty
Defra published research on the uncertainty in the estimates as part of a previous report on consumption-based CO2 emissions between 1992 and 2004 (Wiedmann et al, 2008ii). The research showed that the relative standard error for total UK CO2 consumption emissions in any one year lies within the range of 3.3 per cent for 1994 and 5.5 per cent for 2004.
Based on the uncertainty estimates mentioned above further research undertaken for the Scottish Government (Stockholm Environment Institute, 2009) estimated that the time series of GHG footprint for Scotland had a relative standard error (RSE) for annual estimates in the region of ±5% for CO2 and in the region of up to ±10% for other GHGs. This gave an RSE for all GHGs in the region of ±7%. Since then there have been a number of improvements in the model which should have reduced the range of errors in recent years.
Email: John Landrock
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