This metric is based on the Global Reporting Initiative (GRI) Standard Guidelines. 

In 2018, the GRI G4 Sustainability Reporting Guidelines were superseded by the GRI Sustainability Reporting Standards (GRI standards). For this metric, the code G4-EN17-a is used in company reporting prior to 2018, and the new GRI 305-3 code used in reporting from 2018 onwards. The methodology for the former G4 standard for this metric can be found here. 

In the context of the GRI Standards, the environmental dimension of sustainability concerns an organization’s impacts on living and non-living natural systems, including land, air, water and ecosystems.

GRI 305 addresses emissions into air, which are the discharge of substances from a source into the atmosphere. Types of emissions include: greenhouse gas (GHG), ozone-depleting substances (ODS), and nitrogen oxides (NOX) and sulfur oxides (SOX), among other significant air emissions.

GHG emissions are a major contributor to climate change and are governed by the United Nations (UN) ‘Framework Convention on Climate Change’ and the subsequent UN ‘Kyoto Protocol’. This Standard covers the following GHGs:

• Carbon dioxide (CO2)
• Methane (CH4)
• Nitrous oxide (N2O)
• Hydrofluorocarbons (HFCs)
• Perfluorocarbons (PFCs)
• Sulphur hexafluoride (SF6)
• Nitrogen trifluoride (NF3)

Some GHGs, including methane, are also air pollutants that have significant adverse impacts on ecosystems, air quality, agriculture, and human and animal health.

As a result, different national and international regulations and incentive systems, such as emissions trading, aim to control the volume and reward the reduction of GHG emissions.

The GHG Protocol has established a classification of GHG emissions called ‘Scope’: Scope 1, Scope 2 and Scope 3. The GHG emissions standard published by the International Organization for Standardization (ISO), ‘ISO 14064’, represents these classifications of Scope with the following terms:

• Direct GHG emissions (Scope 1): GHG emissions from sources that are owned or controlled by an organization
• Energy indirect GHG emissions (Scope 2): GHG emissions that result from the generation of purchased or acquired electricity, heating, cooling, and steam consumed by an organization
• Other indirect GHG emissions (Scope 3): Indirect GHG emissions not included in energy indirect (Scope 2) GHG emissions that occur outside of the organization, including both upstream and downstream emissions