Global Warming Potentials
The CAT uses Global Warming Potential (GWP) values from the IPCC’s Fourth Assessment Report (AR4) for all figures and time series. Assessments completed prior to December 2018 (COP24) used GWP values from the IPCC’s Second Assessment Report (SAR).
The historical emissions data was obtained from the National Inventory Report 2018 (Department of Industry Science Energy and Resources, 2020b). The 2019 data in this report is preliminary. All emissions data is reported in financial years for Australia. Australia’s emissions inventory was recalculated compared to previous reports, see the inventory for detail (Department of Industry Science Energy and Resources, 2020b). Recalculations of historical data have repercussions for meeting the NDC target (see below) and on the starting point for projections data.
NDC and other targets
For the 2030 pledge, we have estimated levels of emissions excluding LULUCF resulting from the NDC by subtracting projected emissions for the LULUCF sector in 2030 from the targeted level including LULUCF.
Government recalculations for historical emissions have changed the base year (2005) making the NDC target easier to achieve. There is a 1% (from 611 to 617 MtCO2e) difference between the total emissions including LULUCF in 2005 (NDC target base year) from the National Inventory Report 2017 compared to the National Inventory Report 2018 (Department of Industry Science Energy and Resources, 2020b). LULUCF in 2005 was recalculated with a 5% difference (from 89 to 91 MtCO2e) between these reports, and total emissions excluding LULUCF saw a 1% change (from 522 to 526 MtCO2e) in 2005.
The National Inventory Report attributes the data changes to recalculations made in several sectors. Data changes in the industry sector are a result of atmospheric measurements used to estimate synthetic GHG emissions (Department of Industry Science Energy and Resources, 2020b). For fugitive emissions, new methane estimates have been introduced drawn from methods of the IPCC, increasing methane emissions by 7% (Department of Industry Science Energy and Resources, 2020b). The Australian Government uses Full Carbon Accounting Model (FullCAM) to model the LULUCF sector, and data changes reflect recommendations from UNFCCC Expert Review Team (ERT) (Department of Industry Science Energy and Resources, 2020b). The Australian Government expects future improvements to FullCAM and subsequent data changes (Department of Industry Science Energy and Resources, 2020b).
For a detailed description of LULUCF accounting rules used to calculate the Kyoto targets and 2020 pledge, please consult our Australia report.
Current policy projections
The current policy projection is based on Australia’s Emissions Projections 2019 report (DEE, 2019a). The projections data is harmonized to historical data. The CAT always provides current policy projections excluding LULUCF. To this end, we subtracted the projections provided for LULUCF. Where LULUCF is included for comparison purposes, we use a range from the 2018 and 2019 government projections reports. The range is used given the high uncertainty of this sector, the questionable assumptions in the LULUCF 2019 projection report and the large differences between government annual projections (DEE, 2019a; Department of the Environment and Energy, 2018).
We applied a novel method to estimate the COVID-19 related dip in greenhouse gas emissions in 2020 and the deployment through to 2030. The uncertainty surrounding the severity and length of the pandemic creates a new level of uncertainty for current and future greenhouse gas emissions. We first update the current policy projections using most recent projections, prepared before the pandemic (as above).
We then distil the emission intensity (GHG emissions/GDP) from this pre-pandemic scenario and apply to it most recent GDP projections that take into account the effect of the pandemic. The CAT used the GDP from Australia’s Fourth Biennial Report, which uses the same emissions projections and assumptions as the Emissions Projections 2019 report to estimate the pre-pandemic emissions intensity (Australian Government, 2019b; DEE, 2019a).
To capture a wide range, we compare several GDP projections to account for the pandemic. The CAT compared scenarios from the International Monetary Fund (IMF), Organisation for Economic Co-operation and Development (OECD) and the Reserve Bank of Australia (IMF, 2020; OECD, 2020; RBA, 2020). The CAT calculations are based on the largest range of scenarios available, and then choosing the maximum and minimum emissions out of all the scenarios to create a maximum and minimum range. The range was calculated in financial years to match Australian emissions data reporting. The CAT applies the GDP growth rate of the Fourth Biennial report (original pre-pandemic current policy scenario) for GDP beyond the years that each scenario reported.