Appendix A

Summary of methodological changes to 2019 STIGGI

  • Each year the Australian Government reviews how it calculates greenhouse gas emissions to ensure national and state inventories reflect the latest available data, improved modelling techniques, and any changes in sectoral classifications and estimation methodologies.
  • The recalculations are undertaken according to the Australian Government’s National Inventory Systems Inventory Improvement Plan, which aims to reduce existing emission estimate uncertainties, with development focused on key source categories, sources with high uncertainties, where implementation of new methods is feasible, and in response to international expert reviews (the 2018 National Inventory Report was subject to the most recent UNFCCC review).
  • This revision process includes the recalculation of historical emissions data between 1990 and 2019, nationally and for Tasmania, to ensure that the estimates of emissions are accurate, transparent, complete, consistent through time and comparable with those produced in other countries.
  • The recalculations undertaken for both the 2018 STGGI and 2019 STGGI have resulted in significant changes in Tasmania’s emissions figures across all sectors but especially in the land use, land use change and forestry (LULUCF) sector.
  • As a result of these recalculations, the emissions figures in the State and Territory Greenhouse Gas Inventories 2019 (2019 STGGI) are not directly comparable to the figures published in the STGGI reports of previous years.

Revisions in Tasmania’s emissions between the 2018 STGGI and 2019 STGGI

  • The effect of the recalculated data on Tasmania’s net emissions shows that:
    • Tasmania’s net emissions figure in the baseline year of 1990 is revised up by 0.47 Mt CO2-e to 19.64 Mt CO2-e.
    • Tasmania’s net emissions figure in 2018 is revised down by 0.63 Mt CO2-e to minus 2.82 Mt CO2-e.
    • The reduction in Tasmania’s net emissions figure between 1990 and 2018 is revised up from 105.0 to 114.4 per cent.
    • Tasmania’s net emissions figures are wholly revised down, resulting in Tasmania first achieving net negative emissions in 2013 rather than 2015 as reported in the 2018 STGGI.
  • Table 2 presents a summary of the changes in Tasmania’s 2018 emissions by sector and energy sub‑sector between the 2018 STGGI and 2019 STGGI. It shows that the recalculations have resulted in changes across all sectors. The most significant change is concentrated in the LULUCF sector. This is replicated across the time series.
  • When compared with the 2018 STGGI, methodological changes in the 2019 STGGI have had different effects in LULUCF emissions data since 1990. The changes have resulted in a decrease in emissions in the LULUCF sector of approximately 0.61 Mt CO2-e in 1990 and an increase in the net sink provided by the LULUCF sector of approximately minus 0.84 Mt CO2-e in 2018.

Table 2 – Revisions to Tasmania’s emissions for 2018 by sector and energy sub-sector, following recalculations

Sector/Sub-sector

2018 Emissions (Mt CO2-e)

Change

(Mt CO2-e)

Data from the
2018 STGGI

Data from the
2019 STGGI

Energy (including fugitive emissions)

3.83

3.91

0.08

- Direct combustion

1.78

1.77

-0.01

- Transport

1.59

1.68

0.09

- Electricity generation

0.47

0.47

0.00

Agriculture

2.29

2.45

0.16

IPPU

1.72

1.65

-0.07

Waste

0.35

0.39

0.04

LULUCF

-10.39

-11.23

-0.84

Total

-2.19

-2.82

-0.63

  • The main methodological changes in the sub-categories that have materially contributed to the revision in Tasmania’s emissions between the 2018 STGGI and 2019 STGGI are summarised in Table 3.

Table 3 – Methodological changes and data revisions contributing to change in Tasmania’s emissions between the 2018 STGGI and 2019 STGGI

Sector/Sub-sector

Methodological Change

Energy

Transport

Recalculations were made in response to revisions to Australian Energy Statistics fuel consumption data. Minor adjustment to 2016 and 2017 in road transport resulted from revisions to the allocated fuels between vehicle types within road transport.

Agriculture

Manure management

Recalculations were made due to a revised N2O emission factor for beef cattle feedlots.

Agricultural soils

Recalculations were made due to revised N2O emission factor for the cultivation of histosols and revised cropland remaining cropland activity data throughout the time series, impacting emissions from mineralisation due to loss of soil carbon.

IPPU

Mineral industry

Recalculations were made due to updates to construction industry indexes from 2011 – 2017 published by the ABS.

Metal industry

Recalculations were made were made by deriving historical reductant use in ferroalloys and other metals from production data for 1990 – 2008.

Product uses as ozone depleting substance substitutes

Recalculations were made to the entire time series arising from revised atmospheric calibration of annual leakage rates, revised HFC destruction activity data, and revised retirement parameters for split system air conditioning equipment.

Waste

Solid waste disposal

Recalculations were made in response to revisions in solid waste disposal reported in the National Greenhouse and Energy Reporting System and the National Waste Database

LULUCF

Forest land remaining forest land

Recalculations were made in the other native forest sub-category due to updates for:

  • spatial simulation of prescribed fires using FullCAM; and
  • carbon stock changes from the combustion and subsequent recovery of live biomass from prescribed fires.

Recalculations were made in the pre-1990 plantations sub-category due to updates for:

  • spatial observations of forest cover change; and
  • revised weather and climate data using improved methodology.

Land converted to forest land

Recalculations were made due to updates for:

  • spatial observations of forest cover change;
  • soil cover factor improvements in timing and scope of events determining agricultural plant cover; and
  • non-temperate fire spatial data.

Grassland remaining grassland

Recalculations were made due to updates for:

  • land areas and land-use allocations across the LULUCF sectors;
  • non-temperate fire spatial data; and
  • soil cover factor improvements in timing and scope of events determining agricultural plant cover.

Land converted to grassland

Recalculations were made due to updates for:

  • spatial observations of forest cover change;
  • non-temperate fire spatial data;
  • soil cover factor improvements in timing and scope of events determining agricultural plant cover; and
  • stratified emission factor values based on both soil type and climate zone.

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