Public bodies climate change duties: putting them into practice, guidance required by part four of the Climate Change (Scotland) Act 2009

ANNEX A QUICK GUIDE: GREENHOUSE GAS EMISSIONS

What are greenhouse gases?

'Carbon' is the broad term used to cover the six greenhouse gases ( GHGs) which form the basis of the emissions reduction targets set in the Climate Change (Scotland) Act. These are: carbon dioxide (CO ₂); methane (CH ₄); nitrous oxide (N ₂O); perfluorocarbons ( PFCs); hydrofluorocarbons ( HFCs); and sulphur hexafluoride (SF ₆). Each of the gases has a different warming effect on the atmosphere when released and so to account for this we apply a scaling factor and refer to them in terms of their carbon dioxide equivalent impact, CO ₂e.

Greenhouse gas emissions are reported as annual flows - in tonnes of CO ₂e.

The majority of Scottish GHG emissions are of CO ₂. CH ₄, N ₂O and the three fluorinated gases are produced in smaller quantities, but are more powerful in their greenhouse effect per unit volume than carbon dioxide. Human activities can increase the concentrations of these gases in the atmosphere. Table 1 outlines the six greenhouse gases and their main sources from human activity.

Table 1 - Greenhouse gas types and their main sources

Scotland's Greenhouse Gas emissions

In Scotland in 2008, net emissions of greenhouse gases were 56.1 million tonnes of carbon dioxide equivalent (Mt CO ₂e). Figure 1 (following) shows the sources of these emissions. It is important to note that some land uses and land use changes (particularly conversion of land to forestry) act to absorb some emissions.

Figure 1 - Sources of Scottish Greenhouse Gases by sector, 2008 ⁵⁷

Scotland accounts for approximately 0.15% of all global greenhouse gas emissions due to human activities. As Scotland only has around 0.08% of the world's population, it is clear we produce a far greater level of emissions per person than the average. In 2008, Scotland's net greenhouse gas emissions were made up of 79% carbon dioxide emissions and 21% of the other five greenhouse gases.

Scotland's bogs, wetland and upland systems act as a vital 'carbon bank'. Scotland's organic soils hold 10,028 Mt CO ₂e ⁵⁸ , this compares with a total of 418 Mt CO ₂e in UK surface vegetation ⁵⁹ . To put this into context, Scotland's net 2008 greenhouse gas emissions equate to around 0.6% of Scotland's total soil carbon bank.

The emissions set out above are known as Scotland's territorial emissions, also called 'production' emissions. The national targets are based on these production emissions - plus emissions from international aviation and international shipping. There are two main types of emissions inventories: consumption-based inventories and those based on production. A consumption-based inventory includes all emissions arising from the consumption of goods and services, no matter where the emissions arise globally. A production-based inventory will include all emissions arising from the production process of goods and services within a specified geographical boundary - such as Scotland. The Climate Change (Scotland) Act requires reporting on consumption based emissions alongside progress against the national production-based targets.