Request for Review and Withdrawal of Government Policies Based on SSP5-8.5 / RCP8.5 Climate Scenarios

Letter to Council 8 June 2026

Dear Mayor, Chief Executive and Councillors

We request that the Kapiti Coast District Council review all policies, plans, hazard assessments, infrastructure strategies, and regulatory decisions that rely on the SSP5-8.5/ H+ or RCP8.5/H+ climate scenarios.

Recent developments in climate science indicate that these high-emissions scenarios are no longer considered plausible future pathways. Scientists developing scenarios for the IPCC Seventh Assessment Report (AR7) have concluded that SSP5-8.5 does not reflect current emissions trends, energy transitions, technological developments, or climate policies. As a result, SSP5-8.5 is not expected to be included as a plausible future scenario in the new AR7 framework.

This has important implications for local government planning. If Council decisions relating to coastal hazards, managed retreat, land-use restrictions, infrastructure investment, flood planning or long-term financial planning are based on scenarios now considered implausible, there is a risk that future hazards, costs, and planning responses may have been overstated.

As your constituents, we expect Council decisions to be based on the best available, up-to-date scientific evidence. Continuing to rely on outdated assumptions may undermine public confidence and expose the Council to unnecessary costs and potential legal challenges.

We therefore request that Council:

1. Identify all current policies, plans, strategies, and hazard assessments that rely on SSP5-8.5/H+ or RCP8.5/H+.
   
2. Pause any new measures that are substantially dependent on these scenarios until they have been reviewed.
   
3. Publicly disclose the extent to which current climate planning relies on SSP5-8.5/H+ or RCP8.5/H+ projections.
   
4. Give written assurances that future decisions are based on realistic, evidence-based scenarios rather than extreme pathways now regarded as implausible.
   

Climate change continues to be a key factor in long-term planning. Nevertheless, effective governance involves revising planning assumptions as scientific knowledge advances. Reassessing SSP5-8.5/H+ gives the Council an opportunity to ensure its policies remain proportionate, transparent, and evidence-based.

We would appreciate a written response confirming whether Council intends to review its climate-related policies and planning assumptions in light of these developments.

Regards
Kapiti CALM

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Letter to Government June 2026

Dear Prime Minister, Ministers, and Members of Parliament,

We are writing to respectfully request that the New Zealand Government undertake a comprehensive review of all legislation, regulations, policies, plans, strategies, economic assessments, infrastructure planning frameworks, and public investment decisions that rely substantially on the SSP5-8.5 or RCP8.5 climate emissions scenarios.

Recent developments within the climate science community strongly suggest that these high-end emissions pathways are no longer credible as realistic forecasts of future global emissions. Experts involved in preparing the scenarios for the IPCC Seventh Assessment Report (AR7) have increasingly recognized that the assumptions underlying SSP5-8.5 are fundamentally at odds with current and projected trends in energy technology, decarbonisation efforts, emissions intensity, demographic shifts, and climate policy. This growing consensus underscores the urgent need to reassess and move beyond these outdated models. 

As a result, these scenarios are no longer considered realistic “business-as-usual” futures and are increasingly being treated as extreme sensitivity cases rather than likely outcomes.

These developments raise important questions about the continued use of SSP5-8.5 and RCP8.5 as foundational assumptions in public policy and regulatory decision-making. Where such scenarios have been used as the primary basis for forecasting climate impacts, economic costs, infrastructure risks, insurance exposure, land-use restrictions, or adaptation measures, there is a risk that resulting policies may be influenced by projections that no longer reflect the most probable future pathways.

Good public policy depends on using the best available evidence. As scientific knowledge evolves, governments have a responsibility to review and update the assumptions underpinning major policy decisions, particularly when those decisions have significant economic, social, financial, regulatory, or property-rights implications for New Zealanders.

Accordingly, we respectfully request that the Government:

1. Review the scientific justification for the continued use of these scenarios in government guidelines and policy.
   
2. Reassess climate-related risk assessments, economic analyses, infrastructure planning(including flood mapping), and adaptation strategies that have been materially influenced by SSP5-8.5 or RCP8.5 projections.
   
3. Ensure that future climate planning and decision-making are based on a range of realistic, evidence-based scenarios that appropriately distinguish between likely outcomes and highly improbable worst-case possibilities.
   

This request should not be misunderstood as opposition to climate science, emissions reduction efforts, or prudent climate-risk management. Instead, it underscores a firm commitment to evidence-based policymaking, transparency, accountability, and proportionality. For climate policy to be truly effective, decisions must be rooted in the most current scientific understanding, with policymakers clearly differentiating between plausible futures and highly unlikely scenarios.

New Zealanders have the right to be confident that public policy is grounded in realistic assumptions and that critical regulatory, financial, planning, and investment decisions are not influenced by emission scenarios that many leading climate scientists now consider implausible.

We therefore urge the Government to initiate a comprehensive review of all climate-related policies, planning frameworks, risk assessments, and regulatory instruments that rely upon SSP5-8.5 or RCP8.5 and to update those frameworks where necessary to ensure consistency with the latest scientific evidence.

Thank you for your consideration of this important matter.

We look forward to your response and to learning what steps the Government intends to take to ensure that New Zealand’s climate policies remain scientifically robust, transparent, and proportionate.

Regards
Kapiti CALM