Global warming potentials

Suggested Reading

02 June 2022

NGER

Are your NGER reporter details up to date in the Client Portal?

We are asking all NGER reporters to log in to the Client Portal to review and update your organisation’s user details.

The self-service module in the client portal allows organisations to add, edit or remove:

Executive Officers
NGER Contact Persons
Nominated Report Submitters, and
other EERS users (depending on the role selected, users will have the ability to perform different tasks in EERS).

Note: only users with the 'organisation administrator' role can create, modify or remove other users.

The EERS self-service user guide explains how you can add, edit or remove users who can access your organisation within EERS.

The Clean Energy Regulator is available to support you in updating your details. Please contact us.

Global warming potentials (GWPs) are values that allow direct comparison of the impact of different greenhouse gases in the atmosphere by comparing how much energy one tonne of a gas will absorb compared to one tonne of carbon dioxide.

Updates to these values are periodically undertaken by Intergovernmental Panel on Climate Change (IPCC) to take into account an improved scientific understanding of the physical properties of these gases. The Parties to the Paris Agreement, which includes Australia, adopted the GWPs provided by the in its Fifth Assessment Report (AR5) for the purpose of international greenhouse gas inventory reporting. Previously used GWPs were set in the Second Assessment Report (AR2) and Fourth Assessment Report (AR4).

Emissions factors for NGER reporting have been updated

From 1 July 2020, amendments to the National Greenhouse and Energy Reporting Regulations 2008 and the National Greenhouse and Energy Reporting (Measurement) Determination 2008 for updates to GWPs mean that the for all greenhouse gases reorted under NGER except CO₂ have changed. This means that for the 2020–21 reporting year, several emissions factors used for calculating non-CO₂ gases used in National Greenhouse and Energy Reporting (NGER) have been revised.

The NGER legislation is updated with these GWP changes to maintain the accuracy and comparability of Australia's national emissions estimates with the global community. This is the second time GWPs have been changed since NGER was established. The below table shows a summary of the GWPs for different greenhouse gases that apply to specific NGER reporting years.

Greenhouse gas	AR2 GWPs (2008–09 to 2014–15)	AR4 GWPs (2015–16 to 2019–20)	AR5 GWPs (2020–21 onwards)	2020–21 GWPs / 2019–20 GWPs
Carbon dioxide	1	1	1	0%
Methane	21	25	28	12%
Nitrous oxide	310	298	265	–11%
Perfluoromethane (tetrafluoromethane)	6,500	7,390	6,630	–10%
Perfluoroethane (hexafluoroethane)	9,200	12,200	11,100	–9%
Sulphur hexafluoride	23,900	22,800	23,500	3%
Hydrofluorocarbons(HFCs)	dependent on HFC type	dependent on HFC type	dependent on HFC type	dependent on HFC type

What this means for comparing NGER data across years

Data reported under NGER will not be changed to account for the GWP changes because they reflect the requirements of the NGER legislation that were in force at the time. Therefore, in order to compare data that was reported using different GWPs, you will need to adjust one of the years to match the other. This is needed to ensure consistency through the time series and enables identification of real changes in emissions rather than changes due to varying emissions estimation methods.

The agency publishes NGER data on our website by 28 February each year, including comparisons with data from previous years. Please note that data which is published by the Clean Energy Regulator that compares emissions between years has already been adjusted to accommodate changes in GWPs.

How to convert historical emissions data to the current GWPs for trend analysis

If you wish to convert emissions from one GWP to another, you first divide the tonnes of carbon dioxide equivalent emissions by the GWP of the gas that was used for calculating those emissions. This reverts the tonnes of carbon dioxide equivalent emissions back to tonnes of greenhouse gases. The greenhouse gas is then multiplied by the new GWP.

Example on how to convert emissions

If a facility reported 100,000 t CO₂-e of methane emissions in 2019–20 and you want to compare it to 120,000 t CO₂-e of methane emissions reported by that same facility in 2020–21. Without converting them to the same GWP, at first glance it looks like there was a 20% increase in methane emissions at this facility.

From the table above, the GWP used for methane in 2019–20 is 25. Therefore, the first step is to divide 100,000 by 25. This has converted 100,000 t CO₂-e of methane into 4,000 tonnes of methane.

The second step is to multiply the tonnes of methane by the GWP for 2020–21. From the table above, the GWP used for methane in 2020–21 is 28. Therefore, 4,000 tonnes of methane multiplied by 28 results in 112,000 t CO₂-e of methane.

When you compare this converted value of 112,000 t CO₂-e of methane, instead of the original 100,000 t CO₂-e of methane, there was actually a 7.1% increase between 2019–20 and 2020–21. The original 20% increase was overstated due to the effect of the changing GWPs.