Modelling

The inputs, assumptions, data we used in our modelling and source code for the models we used to get to our final advice

We used four models to inform our analysis and recommendations to government in Ināiatonunei: a low emissions future for Aotearoa. Here we set out the assumptions we put into the models, and the results we got out. 

Since consultation, we have updated the models and assumptions used to support our final advice in Ināiatonunei: a low emissions future for Aotearoa. We have also run sensitivity analysis to help understand how changes in assumptions change the results we get from the models. 

The modelling which supported our draft advice is available here: data and modelling

More material will be progressively added to this page. 

Model release 

The Commission’s three models will be released progressively throughout June and July:  

Climate Policy Analysis (C-PLAN) economic model

We used the C-PLAN model to understand the overall impact of our recommended emissions budgets on GDP and the economy.

C-PLAN is a computable general equilibrium (CGE) model that takes data on the interactions between economic actors to understand how the structure of the economy could be affected by policy.

C-PLAN is programmed in GAMS. This is a specialised modelling software typically used for CGE models. Users will need experience and knowledge running this software.

We are providing two public versions of this model for those that have expressed interest in it. These are pre-programmed with input assumptions for our draft advice and calibrated to the current policy reference case in our draft advice. This will be updated with input assumptions and calibrated to our updated current policy reference case for our final advice by the end of July 2021.

  1. The base package: this is a source-code only version of the model. This version does not contain all the data required to run the model. It is for people interested in the source code.

  2. The full package: this holds the source code, underlying data to run the model and input assumptions for our draft advice. To access this, you will need to provide us with proof that you hold a license for the GTAP 10 database. You will also need to hold a license for the GAMS programming language. The Commission is not able to provide technical assistance in running the model.

For access to either of these, please download, read and sign the C-PLAN license agreement (PDF 92 KB) and return to us at hello@climatecommission.govt.nz.

We do have other information to help you understand C-PLAN.

We will continue to improve C-PLAN over time, and will update the public version as appropriate.

Distributional Impacts Microsimulation for Employment (DIM-E)

Source code and supporting documentation release date TBC – before end July 2021.  

Energy and Emissions in New Zealand (ENZ)  

Source code and supporting documentation release date TBC – before end July 2021.  

The public license agreements for these models will be available on this web page. If you would like a copy of one of the models, you will need to download, read and sign the license agreement and return to us at hello@climatecommission.govt.nz  

The fourth model that we used in our analysis is a proprietary model owned by EnergyLink. 

Scenarios and paths dataset

ENZ scenarios dataset for 2021 final advice (4.2 MB) 
Contains modelling results for the Current Policy Reference case, long-term scenarios to 2050, demonstration path and alternative paths to 2035. 

ENZ assumptions and inputs for 2021 final advice (449 KB) 
Contains scenario assumptions and detailed modelling inputs which were used to create the scenarios and paths and undertake sensitivity analysis in the ENZ model. 

Macroeconomic modelling results and dataset  

C-PLAN GDP results and sensitivities for 2021 final advice (PDF 173 KB)
Contains GDP results from the C-PLAN model runs of the demonstration path and sensitivity analyses that we drew on in our advice. 

C-PLAN input assumptions for 2021 final advice (PDF 566 KB)
Contains detailed technical assumptions which were used in the C-PLAN model.

C-PLAN results for the demonstration path for 2021 final advice (PDF 3 MB)
Contains all results from the C-PLAN model runs of the demonstration path that we drew on in our advice.

C-PLAN results for slow EV uptake for 2021 final advice (PDF 3 MB)
Contains all results from the C-PLAN model runs of the demonstration path with slower uptake of electric vehicles.

C-PLAN results for slow farm practice change and slow EV uptake for 2021 final advice (PDF 1.2 MB)
Contains all results from the C-PLAN model runs of the demonstration path with slower farm practice change and slower uptake of electric vehicles.

Distributional impacts (employment) modelling results 

DIM-E results dataset for 2021 final advice PDF 234 KB)Contains results from the demonstration path from the distributional impacts employment model (DIM-E) that we drew on in our final advice.  

Motu – Expected Distributional Impacts Climate Change Policy on Employment (7.4 MB)A working paper by Motu Economic and Public Policy Research outlining the methodology and the full set of results from the DIM-E modelling. 

Note that a major input to this work is modelling results from C-PLAN. The C-PLAN input assumptions are linked above. 

Electricity market modelling

To come by 18 June:
Electricity market modelling datasets for 2021 final advice: Contains raw results from the demonstration path and sensitivity analyses from the electricity market modelling, a summary of inputs, and scenario and sensitivity descriptions.

Please note that this modelling exercise was complementary to ENZ, our main modelling tool. The purpose was to draw further insight and validate the approach undertaken in ENZ.

NDC calculations 

NDC calculator for 2021 final advice (PDF 302 KB)Contains the data and calculations used to assess the compatibility of the current Nationally Determined Contribution with contributing to the global 1.5ᵒC effort. 

The spreadsheet has several primary functions: 

  • Calculates the budget of allowed emissions for a given NDC target level in 2030
  • Calculates the comparison NDC budgets of allowed emissions based on the modelled rates of reductions of different gases from the IPCC’s Special Report on 1.5ᵒC
  • Calculates the implied target for 2030 on a comparable basis to the current NDC of any given NDC budget.

The calculator can use either the GWP values from the IPCC’s Fourth Assessment Report (AR4 values) or from the IPCC’s Fifth Assessment Report (AR5). The methodologies used here are described in Chapter 13 of our 2021 Supporting Evidence. 

Figures in Ināia tonu nei: a low emissions future for Aotearoa

To come by 18 June:
Charts and data for 2021 final advice: Contains the underlying data for all of the figures in the final advice in Ināia tonu nei: a low emissions future for Aotearoa.

Expert review of our modelling 

Our emissions budgets are informed by evidence from economic models. They have been developed by internationally renowned experts, and experts from Aotearoa and around the world reviewed them prior to the release of our draft advice. Our economic models are robust and fit for purpose.  

Expert reviewers said that they were “impressed by both the scope and detail of the modelling efforts, and believe that these provide a robust quantitative framework to support ambitious climate policy proposals for Aotearoa”. Our economy wide model C-PLAN was also described as being ‘best in class’. 

The reviews give us confidence that our models help us to produce the best possible evidence to support our emissions budgets.  

Since we released our draft advice, we have carried out sensitivity analysis as suggested by the experts. Details of this sensitivity analysis can be found in Chapter 7 and Chapter 8 of Ināia tonu nei: a low emissions future for Aotearoa.  

The reviews can be accessed here: 

Weitzel Vandyck Model Review.pdf  

Daigneault Model Review.pdf 

Stroombergen Model Review Part 1.pdf 

Stroombergen Model Review Part 2.pdf 

Hafstead Model Review Part 1.pdf

Hafstead Model Review Part 2.pdf