Scottish greenhouse gas emissions annual target report: 2014

Part 2 - Net Scottish emissions

Requirements of the Act

Section 34 of the Act requires that, in respect of each greenhouse gas, the report must:

• state the amount of net Scottish emissions for the baseline year (subsection (1)(a)).
• state the amount of net Scottish emissions for the target year (subsection (1)(b)).
• state whether the amount of net Scottish emissions represents an increase or decrease compared to the equivalent amount for the previous target year (subsection (1)(c)).
• identify the methods used to measure or calculate the amount of net Scottish emissions (including in particular any change to those methods) (subsection (1)(d)).

The report must also set out the aggregate amount for the target year of net Scottish emissions (subsection (2)).

If the method of measuring or calculating net Scottish emissions changes and that change is such as to require adjustment of an amount for an earlier target year, the report must specify the adjustment required and state the adjusted amount (subsection (6)). An adjustment must, in so far as reasonably practicable, be made in accordance with international carbon reporting practice (subsection (7)).

Net Scottish emissions of each greenhouse gas

Table 2 provides data for each of the seven greenhouse gases covered by the Act. This includes details of:

• The amount of net Scottish emissions for the baseline year, and for 2014 (the target year);
• Whether any of those amounts represent an increase or decrease compared to the equivalent amount for the previous year; and
• The aggregate amount for 2014 of net Scottish emissions.

Table 2: Net Scottish emissions for each greenhouse gas ( tCO ₂e)

Greenhouse gas	Base year	Net base year emissions	Net Scottish emissions 2013	Net Scottish emissions 2014	Change in net Scottish emissions 2013 - 2014
Carbon dioxide CO 2	1990	55,132,158	38,540,505	34,404,813	-4,135,692
Methane CH 4		17,677,260	7,877,608	7,517,849	-359,760
Nitrous oxide N 2O		4,168,748	3,269,534	3,281,030	+11,496
Hydrofluorocarbons HFCs	1995	126,891	1,303,986	1,327,211	+23,225
Perfluorocarbons PFCs		115,777	98,548	142,008	+43,460
Sulphur hexafluoride SF 6		36,021	31,295	30,940	-355
Nitrogen trifluoride NF 3		501	254	279	+25
Aggregate net greenhouse gas emissions		77,257,355	51,121,730	46,704,130	-4,417,600

Methods used to measure or calculate the amount of net Scottish emissions

The basket of greenhouse gases consists of carbon dioxide, methane, nitrous oxide, and hydrofluorocarbons ( HFCs), perfluorocarbons ( PFCs), sulphur hexafluoride ( SF ₆) and nitrogen trifluoride ( NF ₃). Greenhouse gases are weighted by global warming potential ( GWP) and presented in carbon dioxide equivalent units. The GWP for each gas is defined as its warming influence relative to that of carbon dioxide, as specified by the Intergovernmental Panel on Climate Change ( IPCC).

Greenhouse gas emissions estimates are provided by Ricardo Energy and Environment and Aether under contract to the UK Government Department for Business, Energy and Industrial Strategy, the Scottish Government, the Welsh Government and the Northern Ireland Department of Environment. Reports are published on the National Atmospheric Emissions Inventory ( NAEI) website and the latest figures for Scotland are published in the Official Statistics publication Scottish Greenhouse Gas Emissions, 2014, which is based on data published at the same time in Greenhouse Gas Inventories for England, Scotland, Wales and Northern Ireland: 1990-2014.

The greenhouse gas inventory covers anthropogenic sources of greenhouse gas emissions from a wide variety of emissions sources, which require different approaches to their estimation. There are a large number of data sources used in its compilation, obtained from Government statistics, regulatory agencies, trade associations, individual companies, surveys and censuses. The methods used to compile the greenhouse gas inventory are consistent with international guidance on national inventory reporting from the IPCC.

Most emission estimates are compiled by combining activity data (such as fuel use) with a suitable emission factor (such as amount of CO ₂ emitted per unit of fuel used). Estimates of emissions from the industrial sector are often compiled based on plant-specific emissions data. Emissions from some sectors are based on more complicated models - such as the model used to estimate emissions from landfill, and the model used to estimate the carbon dynamics in soils when trees are planted. Much of the data on net emissions from agriculture and related land use, land use change and forestry emissions are based on modelled data for Scotland, which are consistent with, but not constrained to, the UK totals and thus are known as "bottom up" estimates.

Many of the remaining emissions sources within the inventory have been collated on a "top down" approach where estimates of emissions have been apportioned to Scotland using proportions of energy use in the UK Department for Business, Energy and Industrial Strategy publication "Digest of UK Energy Statistics ( DUKES)". This approach is prompted by data availability on emissions being more limited at the sub- UK level.

Changes to methods used to measure or calculate the amount of net Scottish emissions

Scottish greenhouse gas emissions are reviewed every year, and the whole historical data series is revised to incorporate methodological improvements and new data. As a result, both net Scottish emissions and the net Scottish emissions account for each target year are revised every year. The latest published Scottish greenhouse gas inventory (1990-2014) represents the best available data and supersede any previous data, which should be disregarded.

The Scottish greenhouse gas inventory is a subset of the UK inventory, which is assembled using international guidelines that require countries to keep it under review and take account of amongst other things:

• New data and revisions to data;
• International developments in inventory methods;
• The need for the inventory to take account of policy needs as they evolve;
• Results of research.

All of the revisions to the 1990-2014 Scottish and UK inventories were for one of the reasons above.

Revisions for the 1990-2014 inventory

Due to methodological improvements and new data, as described above, the baseline has been revised upwards in every successive inventory between 1990-2008 to 1990-2013, with a downwards revision to the baseline between the 1990-2013 and 1990-2014 inventories.

Despite the downwards revision between the 1990-2013 and 1990-2014 inventories, there has been an overall upward revision to the baseline to 77.3 MtCO ₂e, which is 7.1 MtCO ₂e higher than estimated at the time annual targets for 2010 to 2027 were set based on the 1990-2008 Inventory.

Detailed information on revisions are published in the Official Statistics release Scottish Greenhouse Gas Emissions 2014 (Section D). The most notable revisions are:

Forestry

• Correction to model used to estimate net emissions from forestry and harvested wood products.

Agriculture and Related Land Use

• Correction to emissions of drainage of grasslands on organic soils.
• Impacts of research to derive more representative, UK-specific emission factors to nitrous oxide emissions in the Agriculture and Related Land Use sector.

Adjustment of an amount for earlier target years

Revisions to previously reported estimates of net Scottish emissions for earlier target years are detailed in Table 3.

Table 3: Revisions to net Scottish emissions for earlier target years

Target year	Net Scottish emission estimate previously reported ( tCO 2e)	Revision required ( tCO 2e)	Revised amount ( tCO 2e)
FOR THE 1990-2011 INVENTORY
2010	55,731,486	+ 1,178,969	56,910,455
REASONS FOR REVISIONS. These are detailed in the Annual Target Report for 2011 and in the statistics paper Scottish Greenhouse Gas Emissions 2012 - Key Revisions since 2008
FOR THE 1990-2012 INVENTORY
2010	56,910,455	+ 1,407,176	58,317,632
2011	51,285,207	+ 1,202,036	52,487,243
REASONS FOR REVISIONS. These are detailed in the Annual Target Report for 2012 and in the statistics paper Scottish Greenhouse Gas Emissions 2012 - Key Revisions since 2008
FOR THE 1990-2013 INVENTORY
2010	58,317,632	+ 3,193,550	61,511,182
2011	52,487,243	+ 2,355,503	54,842,745
2012	52,895,245	+ 2,044,311	54,939,556
REASONS FOR REVISIONS. These are described in the Annual Target Report for 2013 and in the Official Statistics publication Scottish Greenhouse Gas Emissions 2013
FOR THE 1990-2014 INVENTORY
2010	61,511,182	-2,513,579	58,997,604
2011	54,842,745	-2,589,800	52,252,945
2012	54,939,556	-2,228,882	52,710,674
2013	52,961,210	-1,839,480	51,121,730
REASONS FOR REVISIONS. These are described above and in more detail in the Official Statistics Release Scottish Greenhouse Gas Emissions 2014

Chart 1 shows the impact of successive revisions of the inventory on the reported source emissions for the baseline and the years from 2010 to 2013, as well as the source emissions for 2014.

Chart 1. Impact of successive revisions of the inventory on the reported source emissions for the baseline and the years from 2010 to 2013, and source emissions for 2014. Values in MtCO ₂e