Request for input: Update to advice on the fourth emissions budget
Modelling assumptions
When we undertake analysis on emissions budgets, we use detailed sector level assumptions to create a bottom-up view of the level of emissions reductions which are feasible across the economy.
As this advice is an update, we will be starting from the modelling used in our previous advice and updating it as required. This will include reflecting updates to the Greenhouse Gas Inventory and latest government emissions projections.
Assumptions which affect biogenic methane emissions may also need to be adjusted to reflect the target change. When we released our original advice on the level of the fourth emissions budget we published an assumptions log, which set out the detailed assumptions used. This can be downloaded here: ENZ assumptions log 23-8-2024 [Microsoft Excel file, 378 KB]
The responses we receive to these questions will inform what assumptions from our original fourth emissions budget advice we may need to change in updating our modelling and how.
What does updating our modelling to reflect updates to the Greenhouse Gas Inventory and latest government emissions projections mean?
Our emissions modelling uses a range of data inputs and assumptions to project emissions into the future. Two key inputs are the Greenhouse Gas Inventory and the government’s emissions projections.
The Greenhouse Gas Inventory is the official annual report of emissions and removals and provides the historic emissions data on which our modelling is based.
Each year the government produces a ‘with existing measures’ emissions projection. This estimates future emissions including the effects of emissions reduction policies currently in place. As part of updating our modelling we produce a ‘reference scenario’ which is similar to the government’s ‘with existing measures’ projection. We use this as the starting point for understanding what further emissions reductions could be possible. Where possible we seek to align the reference scenario with the government 'with existing measures' projection, although complete alignment is not always possible.