Greenhouse gas emissions 2018: estimates

Section A. Introduction to Greenhouse Gases

Purpose of this Publication

The "Scottish Greenhouse Gas Emissions 2018" Official Statistics publication contains the results of the Scottish Greenhouse Gas Inventory for 1990-2018. The Scottish Greenhouse Gas Inventory is the key data source for understanding the origins and magnitudes of the emissions. The inventory is compiled in line with international guidance from the Intergovernmental Panel on Climate Change (IPCC). Data are reported by source sector (such as energy supply) and by greenhouse gas (such as carbon dioxide). The inventory is also used to report data against targets as required under the Climate Change (Scotland) Act 2009.

Using the Statistics. Which measure to use and when?

The official statistics publication "Scottish Greenhouse Gas Emissions 2018" includes data on two categorisations of greenhouse gas emissions.

• Estimated net source emissions. These are sometimes referred to as "territorial" emissions, as they are produced within a country's territory or economic sphere. Section B contains results using this categorisation.
• GHG account. These are net source emissions which have been adjusted to remove the effect of successive revisions to the data over time. Section C contains results using this categorisation.

The publication does not contain information on consumption-based emission estimates. This refers to greenhouse gas emissions which are associated with the spending of Scottish residents on goods and services, wherever in the world these emissions arise together with emissions directly generated by Scottish households, through private heating and motoring. This information was most recently published in December 2019 for the years 1998 to 2016 as part as part of the Official Statistics publication: "Scotland's Carbon Footprint 1998-2016". Section E contains information on what territorial emissions are excluded from the greenhouse gas inventory.

The table below shows how to use the different categorisations of statistics on greenhouse gas emissions.

	Estimated Source Emissions (Section B)	GHG account (Section C)
Used for reporting progress against Scotland's Climate Change Targets 1	˟	✓
Can be compared with EU countries	✓	˟
Can be compared with UK 2	✓	˟
Includes International Aviation and Shipping	✓	✓
Includes North Sea Oil & Gas	˟	˟
Data on individual greenhouse gases	✓	˟
Data on sectoral emissions	✓	˟
Base Year	1990	Baseline Period (Variable)

¹ Further information on Scotland's Climate Change Targets can be found in Section C.

² Direct comparisons between Scotland and the UK can be made by adding up the results for the four Devolved Administrations separately. The UK figure in this case would exclude offshore emissions.

Which greenhouse gases are reported on and how do they contribute to global warming?

The basket of greenhouse gases consists of carbon dioxide, methane, nitrous oxide, and the four F-gases (hydrofluorocarbons- HFCs, perfluorocarbons – PFCs, sulphur hexafluoride- SF₆ and nitrogen trifluoride- NF₃). These gases are weighted by Global Warming Potential (GWP), so that total greenhouse gas emissions can be reported on a consistent basis. The GWP for each gas is defined as its warming influence relative to that of carbon dioxide over a 100 year period. Greenhouse gas emissions are then presented in carbon dioxide equivalent (CO₂e) units. In the case of some of the F-gases, the global warming potential is listed as being within a range of values, due to the gases existing as a variety of isotopes with differing GWPs.

Table A1. List of Greenhouse Gases and their contribution to Scotland's net greenhouse gas emissions, 2018

Name of Greenhouse Gas	Chemical Formula	Global Warming Potential (GWP) (Conversion factor to carbon dioxide equivalent)	Contribution to Scotland's Net Greenhouse Gas Emissions, 2018 (in MtCO2e)	Percentage of Scotland's Net Greenhouse Gas Emissions, 2018 (in MtCO2e)	Examples sources of gas
Carbon dioxide	CO2	1	30.9	74.2%	All other sources of greenhouse gases, including removals (carbon sinks)
Methane	CH4	25	6.3	15.1%	Waste management, enteric fermentation and animal waste
Nitrous oxide	N2O	298	3.2	7.7%	Agricultural soils
F-gases 2			1.2	3.0%	Industrial air conditioning, refrigeration, use as tracer gases, semiconductors
Hydrofluorocarbons	HFC	12 - 14,800	1.1	2.5%
Perfluorocarbons	PFC	7,390 - 17,340	0.2	0.4%
Sulphur hexafluoride	SF6	22,800	0.03	0.1%
Nitrogen trifluoride	NF3	17,200	0.0004	0.0%
Total Net Greenhouse Gases			41.6	100.0%

The Global Warming Potentials (GWPs) are based on international reporting standards, as set by the Intergovernmental Panel on Climate Change (IPCC)^[1].

Section B contains further data on the individual greenhouse gases. Section D contains a more detailed discussion of the causes and impacts of revisions between the 1990-2017 and 1990-2018 inventories.

Reporting of the Baseline Period and 1990

In this publication, a single 1990 Base Year is used for all estimated source emissions (Section B). This year is referred to as "1990" in charts, tables and text.

A different baseline is used for the reporting progress against Scotland's Climate Change Targets, using the GHG account. This is referred to as "Baseline Period" when referring to changes over time in the charts, tables and text.

The Baseline Period for reporting against Climate Change Targets is:

• 1990 for carbon dioxide carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O)
• 1995 for Fluorinated gases (F gases)^[2]: hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulphur hexafluoride (SF₆), nitrogen trifluoride (NF₃)

The difference between these definitions of baseline year tend to be small as F gases are a minority contribution to the total emissions in terms of carbon dioxide equivalent.

Within this publication, data are estimated for the Baseline Period; and the years 1990, 1995 and 1998 to 2018.

What are net emissions and carbon sinks?

The emissions reported are the combination of emissions minus removals from the atmosphere by carbon sinks. Carbon sinks are present in the 'Land use, Land Use Change and Forestry' (LULUCF) category, they are mostly associated with the effects of grasslands and forestry to sequester carbon, as well as the carbon stored in wood products. These are known as "removals" as they offset emissions.

Categories

This publication provides the latest estimates of Scotland's greenhouse gas emissions by source from 1990-2018. It uses the 'National Communication' categories, which are the same categories used for the UK report. Note that previous publications used the Scottish government sectors instead. This was changed for consistency with other reports. However, the data are still available by Scottish Government sectors in the underlying excel database that accompanies this publication. For the purposes of reporting, greenhouse gas emissions are allocated into categories as follows:

Energy supply - Emissions from fuel combustion for electricity and other energy production sources, and fugitive emissions from fuels (such as from mining or onshore oil and gas extraction activities). North Sea oil & gas emissions are not allocated to Scotland^[3].

Business – Emissions from fuel combustion and product use in industrial and commercial sectors, and F gas emissions from refrigeration and air conditioning in all sectors. Includes industrial off-road machinery

Industrial processes - Emissions resulting from industrial processes, except for those associated with fuel combustion which are included in the Business sector.

Transport (excluding International Aviation and Shipping) - Emissions from domestic aviation, road transport, railways, domestic navigation, fishing and aircraft support vehicles.

International Aviation and Shipping – This category is called "Exports" in some inventories. Includes emissions from international aviation and shipping.

Public - Emissions from combustion of fuel in public sector buildings.

Residential - Emissions from fuel combustion for heating/cooling and garden machinery and fluorinated gases released from aerosols/metered dose inhalers.

Agriculture - Emissions from livestock, agricultural soils (excluding

carbon stock changes which are included in the LULUCF sector), stationary combustion sources and off-road machinery.

Waste management - Emissions from waste disposed of to landfill sites, waste incineration, and the treatment of waste water.

Land use, land use change and forestry (LULUCF) – Emissions/removals of CO₂ from changes in the carbon stock in forestland, cropland, grassland, wetlands, settlements and harvested wood products, and of other greenhouse gases from drainage (excl. croplands and intensive grasslands) and rewetting of soils, nitrogen mineralisation associated with loss and gain of soil organic matter, and fires. Because the impact of biomass harvest on carbon stocks in ecosystems is included in this sector, any emissions of CO₂ from burning biomass (regardless of the country of origin) are excluded from other sectors to avoid double counting them.

When emissions are reported by source, emissions are attributed to the sector that emits them directly. These high-level sectors are made up of a number of more detailed sectors, which follow the definitions set out by the Intergovernmental Panel on Climate Change (IPCC), and which are used in international reporting tables which are submitted to the United Nations Framework Convention on Climate Change (UNFCCC) every year. Section E contains a more detailed mapping of what is included in each source. It also contains information on which greenhouse gas emissions are excluded from the greenhouse gas inventory and why they are excluded.

The sector breakdowns in this report are primarily based on the National Communication (NC) sectors, which are used in the UK Greenhouse Gas Inventory. The Scottish Government also reports on International Aviation and Shipping emissions attributed to Scotland, along with other Transport emissions. International Aviation and Shipping emissions are categorised as an IPCC international "Memo" item.