Climate outcomes in flux: NZ's next Emissions Reduction Plan
Warming outcomes from the Government's Emissions Reduction Plan (ERP2) compared to pathways incorporated within the Climate Change Commission's advice
Summary
In an article earlier this year, ‘No additional warming, but relative to when?’, I explored the warming impacts of New Zealand's methane targets using a simple emissions-based climate model, the Finite Amplitude Impulse Response model (FaIR) (Leach et al., 2021).
My prior article article was in part a response to messaging from some quarters of the agricultural industry, who have suggested, among other points, that it is New Zealand’s warming contribution that matters, rather than how emissions may stack up under various accounting guises and metrics.
While in the case of methane, I sometimes find myself furrowing my brow at the reasoning chain that then follows the assertion that it is ‘warming that matters’, I’ll put that aside here.
Instead, with this article, I’ll be taking the notion that it is ‘warming that matters’ to heart, and will be using the same simple climate model, FaIR, to look at the question:
How do the Government's current efforts set out in its draft Emissions Reduction Plan measure up against the Climate Change Commission's advice?
After all, with consultation set to close this week on the Government's Emissions Reduction Plan (ERP2), the first for this new coalition government, it stands as a good time to take stock of how their plans stack-up.
To parse out how the Government’s efforts compare against advice and technical analysis from the Climate Change Commission (the Commission), the following modelled emissions pathways have been run through FaIR:
Government ERP2 scenarios:
Baseline scenario - reflects current committed policies.
Low scenario - low-end plausible emissions for current policies. Includes assumptions about how policies will develop over time, such as a gradual increase in the carbon price facing agriculture from 2030 to 2050.
High scenario - as above, but for the higher-end of plausible emissions.
Commission scenarios:
Demonstration pathways:
2023 demonstration path (ERP Demo) - used as part of the Commission’s 2023 advice informing ERP2.
Fourth emissions budget demonstration path (EB4) - updated pathway consistent with meeting Commission's draft proposals for EB4 (2036-2040).
Variations of technology adoption and pursuit of systems-change:
High technology, high systems change (HTHS) - relatively high technology adoption, high propensity and pursuit of systems changes (e.g., transport modal shifts).
High technology, low systems change (HTLS).
Low technology, high systems change (LTHS).
Low technology, low systems change (LTLS).
To form estimates of New Zealand’s contribution to warming in each scenario, a global background emissions scenario consistent with a 2°C pathway (SSP1-2.6) is used in this article. This choice was made to ensure alignment to the Commission’s draft advice on New Zealand’s 2050 targets that used this background scenario (Commission, 2024d).
Both sets of scenarios draw modelled emissions pathways from the Emissions in New Zealand (ENZ) model, developed by Concept Consulting. Given this, the analysis here offers a reasonable first-order apples-for-apples comparison of the pathways set out by the Government and Commission.
Summary technical notes on steps taken to harmonise emissions datasets, and inconsistencies between the two sets of emissions pathways are set out at the bottom of this article.
The emissions gap
Before diving into warming outcomes, let’s briefly recap the trajectories for emissions of major greenhouse gases (GHGs) in these scenarios.
GHGs other than biogenic methane
First, by examining gross GHG emissions exclusive of biogenic methane in the Government's ERP2, we can see a clear divergence from the Commission's modelled scenarios, trending higher in each of the Government’s low, baseline and high ERP2 scenarios. This is shown in Figure 1 below.
The higher path seen for gross emissions within the Government’s ERP2 shouldn't come as a shock for most readers, given the Government's stated approach of pursuing 'least cost' reductions to meet targets (MfE, 2024b), with markets such as the NZ ETS set to play the determinant role in which mitigation opportunities are pursued.
In principle, the higher-track for gross emissions seen within ERP2 could be balanced out in net emissions and warming-terms with greater levels of removals than those envisaged by the Commission.
However the Government still faces challenges in achieving this. In particular, the current coverage of the NZ ETS, in which nitrous oxide from agriculture is excluded from any obligations, mean that even where levels of removals are greater in order to compensate for the higher track taken in gross emissions covered by the NZ ETS, a sizable portion of nitrous oxide emissions (6.3 million tonnes CO2-e in 2050 in the ERP2 baseline) remain uncovered by policies that would offset these emissions with removals.
Biogenic methane
Turning to biogenic methane in figure 2 below, the Government's ERP2 projections see emissions ranging from 9% to 14% below 2017 levels by 2050, higher than New Zealand's current legislated target range (24 to 47% below 2017 emissions by 2050).
This is not the first set of government projections that have seen methane emissions off-track for New Zealand’s 2050 target range. So while the Government’s delay of the start of pricing of agricultural emissions until the end of the decade will contribute to a higher emissions path, the gap also reflects a more general long-running absence of policies in place to reduce biogenic methane (whether that is through shifts in practises, or adoption of technology).
The recent adoption of SBTi targets and other climate commitments by some agri-food companies (such as Fonterra, Silver Fern Farms, and Synlait) may help to cover for some of this slack. Though other central government policies in the pipeline related to freshwater policy, and restriction of entry of forests to the NZ ETS could see upward pressure on the Government’s biogenic methane projections in future iterations.
Warming outcomes
Warming to 2050 in the ERP2 baseline scenario
So what do these emissions trajectories mean for New Zealand's contribution to warming at a global level?
Figure 3 below highlights New Zealand's contribution to warming from emissions of all GHGs since 1850, with emissions from today reflecting the Government's baseline scenario for ERP2. Under the Government’s ERP 2 baseline scenario, New Zealand’s contributed warming fails to peak by 2050.
As for how things break down per GHG species, additional year-on-year warming from net carbon dioxide emissions tapers off approaching 2050, but still serves as the largest contributor of additional warming above existing levels over this period. Warming from nitrous oxide emissions meanwhile continues to grow out to 2050, with its contributed warming ~28% higher in 2050 than in 2020.
Methane’s cumulative contribution to warming (inclusive of non-biogenic methane from fossil fuel sources) peaks later in the 2020s, before declining slightly and then inflecting back-up approaching 2050.
As covered in my past article on New Zealand’s methane targets, care must be taken when drawing inferences from this picture for methane. Given methane’s warming impact is sensitive to background concentrations of methane itself and other reactive gases and aerosols (Reisinger, Meinshausen and Manning, 2011; Thornhill et al., 2021; Smith et al., 2024), switching the background scenario assumptions used (e.g., to a 1.5°C consistent scenario) sees methane’s estimated warming contribution rising each year through to 2050.
Under an assumed 1.5°C-consistent background scenario [SSP1-1.9], synthetic GHGs were the only species that saw their warming peak ahead of 2050 in the Government’s baseline ERP2 scenario.
Comparing warming under ERP2 to the Commission’s pathways
Figure 4 below sets out how cumulative warming (from all sectors and gases) compares between the Government's ERP2 and the Commission's modelled pathways.
All three modelled scenarios reflecting the Government's ERP2 plans (low, baseline and high) see contributed warming levels above the Commission's pathways. In 2050 for example, warming in the central baseline scenario for ERP2 is about 5% higher at mid-century than the Commission's 2023 demonstration pathway.
The remaining Commission scenarios pictured in Figure 4 (within the orange shaded band) are drawn from its draft advice on New Zealand’s fourth emissions budget (2036-2040), due for release later this year. While these scenarios do not form part of the statutory advice that the Government must consider for ERP2 given their draft status, they nevertheless reflect a clear (and arguably growing) divergence between the Government’s ERP2 and what the Commission’s latest analysis suggests is possible.
The ‘low technology, low systems change’ (LTLS) scenario is, I’d argue, the most interesting to contrast to ERP2 among these. This scenario (Commission, 2024a, p. 65) minimises “societal shifts by focusing on emissions reductions for each activity through proven technology options.” Yet even in this more conservative approach to getting to 2050, the Government’s ERP2 remains a ways behind.
So expect to see further pressure coming back on the Government to bend the curve on emissions and warming when the Commission’s advice on the fourth emissions budget gets tabled later this year. Somewhat awkward timing it must be said given the overlapping timetable in which the ERP2 is set to be finalised.
Breaking down warming between New Zealand’s targets
Finally, it can be useful to take a look at each of New Zealand’s 2050 targets separately when it comes to warming as a sense check of whether efforts more closely match up to the Commission’s advice in one sphere, but not another. For example, can we observe a slower pace of change for biogenic methane emissions (and consequent warming) compensated with a faster pace of change towards New Zealand’s net-zero target?
Up first, we have warming from GHGs emissions excluding biogenic methane, presented inclusive and exclusive of forestry removals. In figure 5 below, the Commission’s EB4 demonstration pathway (shown in orange colouring) is compared to the Government’s baseline ERP 2 (shown in teal/green colouring), with warming disaggregated into net emissions and gross emissions for each.
As seen in Figure 5, ERP2 sees a higher warming path associated with gross emissions other than biogenic methane than the Commission’s EB4 demonstration pathway.
The Commission’s more ambitious path for gross emissions is also coupled with higher rates of annual removals in the EB4 demonstration path than in the Government’s ERP2. Given this, the EB4 demonstration pathway is able to bend the curve on warming associated with New Zealand’s net emissions other than biogenic methane, seeing cumulative warming decreasing from around the mid-2030s.
While the Government cancelled the 2023 ETS Review set-up by the previous government following its election win in late 2023, long-term questions related to the role of the NZ ETS, and how New Zealand plans to offset the warming from emissions currently outside the NZ ETS (e.g., nitrous oxide from agriculture) will still need to be grappled with if the Government is to catch-up to the Commission on this front.
Finally, warming from biogenic methane is set out in figure 6 below, reflecting the difference in warming outcomes between the Government’s ERP2 baseline and the Commission’s EB4 demonstration pathway. Each scenario is modelled using three background scenario assumptions for global emissions given methane’s sensitivity to background concentrations of a range of gases at a global level:
SSP1-1.9 - global emissions are reduced sufficiently to limit warming to 1.5°C (with limited or no overshoot) (Meinshausen et al., 2020).
SSP1-2.6 - warming is limited below 2°C (Meinshausen et al., 2020).
SSP2-2.45 - roughly approximates to current international efforts, with central results for temperature rise reaching 2.8°C above pre-industrial level by 2100 (Matthews and Wynes, 2022; Hueholt et al., 2024).
Figure 6 highlights a point made in my prior commentary on methane targets. Namely that reductions in methane emissions consistent with New Zealand’s current target range (24 to 47% below 2017 emissions by 2050) are sufficient to see warming from biogenic methane constrained or reducing from recent levels under a wide range of background assumptions.
In contrast, pursuing less ambitious targets (such as one in line with the Government’s ERP2 pathway) presents an ambiguous picture as to whether New Zealand’s actions imply stabilised, increased or reduced warming out to mid-century when background assumptions are varied. So while in the core background scenario used in this article (SSP1-2.6), additional warming from biogenic methane is largely ceased, this does not hold true in all background scenario contexts.
Nevertheless, there is only so much that can be gathered by looking at charts of modelled warming outcomes when it comes to targets for biogenic methane. Decisions on the target range ultimately require discussion on New Zealand’s mitigation potential for biogenic methane, how this mitigation potential will be acted upon in policy terms, and equity and fair-effort as part of global efforts to limit warming to 1.5°C.
Summing it up
Across all of the figures examined in this article, contributed warming trends noticeably higher in the Government’s ERP2 than that observed in the Commission’s various modelled pathways used to support its advice to the Government.
It is of course reasonable to allow some time for the Government to further draw up its plans and take on feedback from the ERP consultation window before weighing in too heavily with stark criticism. Yet with warming outcomes seemingly lagging across all sectors and gases, it is fair to say a full court press will be required.
Final parting comments
Firstly, a thank you to all the folks who have subscribed over recent months. It has been humbling to see my subscriber count tick upward, in spite of a lack of articles the past couple months.
Why so quiet? Well I've been working on the set-up and launch of a company to house my consulting work supporting organisations in relation to the NZ ETS, carbon markets and climate policy. As part of this, I've recently launched:
Website for the consulting firm: kapiticlimate.com
forestPy: A free web-based model that can be used to project unit earnings for forests registered in the NZ ETS (including for multiple registered forest areas). kapiticlimate.com/forestPy
If you work for an organisation that needs support in these areas reach out via the contact form on the website linked above.
While for the remainder of you, as ever with modern content channels, liking, sharing and subscribing to this Substack helps immensely!1
Technical notes
Historical emissions prior to 1990 and modelled emissions within the Commission’s pathways (2022-2050) are taken from the Commission’s draft advice on New Zealand’s 2050 targets (Commission, 2024b; 2024d).
Historical (prior to 1990) and future emissions data (from 2022) for carbon dioxide (gross), nitrous oxide, methane and HFCs within the Commission’s dataset have been adjusted by the ratio of means between the 2023 GHG inventory and 2024 GHG inventory to ensure alignment with the ERP2 scenarios that use 2024 inventory data.
Historical PFC emissions were not modified due to apparent inconsistencies in data within the Commission’s dataset in the 1990s to both the 2023 and 2024 inventory. Forecast forestry removals were likewise not modified in the Commission’s scenarios, as changes in reported removals from the 2023 to 2024 GHG inventory relate to improved historical activity data.
Nitrous oxide within the Commission’s 2023 demonstration pathway was replaced with data from the Commission’s EB4 demonstration pathway to correct for its use of older inventory data (affecting the trend in emissions over the 2020s).
The Commission’s 2023 demonstration pathway is left out of figures relating to biogenic methane however due to challenges reconciling emissions in the 2020s related to its calibration to older inventory data.
Other recent developments (such as Tiwai Point continuing) are not incorporated within the Commission’s projected scenarios as it is difficult to judge how the Commission will accommodate this within their finalised modelled pathways for their EB4 advice due later this year.
Government ERP2 emissions data (MfE, 2024a) for energy, transport and industrial processes has not been provided publicly broken down by GHG species. Aggregated ERP2 data for these sectors was disaggregated using the proportional contribution of major gases (carbon dioxide, methane and nitrous oxide) each year per sector within the Government’s late-2023 projections (MfE, 2023). Synthetic GHGs for the ERP2 scenarios were taken directly from the Government’s late-2023 projections (low, central and high scenarios) and allocated to the low, baseline and high scenarios respectively.
References
Climate Change Commission (2024a) Draft advice on Aotearoa New Zealand’s fourth emissions budget. Draft advice. Wellington, New Zealand: Climate Change Commission, p. 162. Available at: https://www.climatecommission.govt.nz/our-work/advice-to-government-topic/preparing-advice-on-emissions-budgets/advice-on-the-fourth-emissions-budget/ (Accessed: 16 August 2024).
Climate Change Commission (2024b) ‘Input data files for temperature modelling’. Available at: https://www.climatecommission.govt.nz/public/Uploads/Targets/supporting-docs/input-data-files-for-temperature-modelling.zip (Accessed: 10 May 2024).
Climate Change Commission (2024c) Modelling and analysis to support the draft advice on Aotearoa New Zealand’s fourth emissions budget. Technical Annex. Wellington, New Zealand: Climate Change Commission, p. 53. Available at: https://www.climatecommission.govt.nz/public/Uploads/EB4/supporting-docs/Technical-Annex-Modelling-and-analysis-9-4.pdf (Accessed: 8 April 2024).
Climate Change Commission (2024d) Review of the 2050 emissions reduction target. Discussion Document. Wellington, New Zealand: Climate Change Commission, p. 96. Available at: https://www.climatecommission.govt.nz/public/Uploads/Targets/supporting-docs/20240404-Target-Consultation.pdf (Accessed: 18 April 2024).
Green, K. (2024) ‘No additional warming, but relative to when?’, Kapiti Climate Insights, 3 June.
Hueholt, D.M. et al. (2024) ‘Speed of environmental change frames relative ecological risk in climate change and climate intervention scenarios’, Nature Communications, 15(1), p. 3332. Available at: https://doi.org/10.1038/s41467-024-47656-z.
Leach, N.J. et al. (2021) ‘FaIRv2.0.0: a generalized impulse response model for climate uncertainty and future scenario exploration’, Geoscientific Model Development, 14(5), pp. 3007–3036. Available at: https://doi.org/10.5194/gmd-14-3007-2021.
Matthews, H.D. and Wynes, S. (2022) ‘Current global efforts are insufficient to limit warming to 1.5°C’, Science, 376(6600), pp. 1404–1409. Available at: https://doi.org/10.1126/science.abo3378.
Meinshausen, M. et al. (2020) ‘The shared socio-economic pathway (SSP) greenhouse gas concentrations and their extensions to 2500’, Geoscientific Model Development, 13(8), pp. 3571–3605. Available at: https://doi.org/10.5194/gmd-13-3571-2020.
Ministry for the Environment (MfE) (2023) ‘Updated emissions projections to 2050 released’. Available at: https://environment.govt.nz/assets/what-government-is-doing/climate-change/2050-historical-and-projected-sectoral-emissions-data-November_2023-for-publishing-v01.xlsx (Accessed: 29 March 2024).
Ministry for the Environment (MfE) (2024a) ‘Emissions Reduction Plan 2: ENZ results for technical annex’. Available at: https://consult.environment.govt.nz/climate/second-emissions-reduction-plan/ (Accessed: 16 August 2024).
Ministry for the Environment (MfE) (2024b) New Zealand’s Second Emissions Reduction Plan (2026–30). Discussion Document. Wellington, New Zealand: New Zealand Government, p. 123. Available at: https://consult.environment.govt.nz/climate/second-emissions-reduction-plan/ (Accessed: 8 August 2024).
Reisinger, A., Meinshausen, M. and Manning, M. (2011) ‘Future changes in global warming potentials under representative concentration pathways’, Environmental Research Letters, 6(2), p. 024020. Available at: https://doi.org/10.1088/1748-9326/6/2/024020.
Smith, C. (2024) ‘FaIR calibration data: version 1.4.0’. Zenodo. Available at: https://doi.org/10.5281/zenodo.8399112.
Smith, C. et al. (2024) ‘fair-calibrate v1.4.1: calibration, constraining and validation of the FaIR simple climate model for reliable future climate projections’, EGUsphere, 2024, pp. 1–36. Available at: https://doi.org/10.5194/egusphere-2024-708.
Thornhill, G. et al. (2021) ‘Effective radiative forcing from emissions of reactive gases and aerosols – a multi-model comparison’, Atmospheric Chemistry and Physics, 21(2), pp. 853–874. Available at: https://doi.org/10.5194/acp-21-853-2021.
Gosh, I feel like a YouTube podcaster saying this.