Katharine Moody says we should tackle climate adaptation planning with a clear understanding of the likelihood of events unfolding, rather than from the perspective of the full range of possibilities

By Katharine Moody*

Last week the Government released a National Adaptation Plan (NAP) covering actions to be taken in the years 2022-28, to build resilience to hazards arising from changing climate. As a non-statutory plan, nothing in it binds anyone to doing anything by law, although the Government has signalled as part of the reform of the resource management system, a new Climate Adaptation Act is to be written. And it is likely that that Act will specify a legal process and mechanism for the implementation of the adaptation option of managed retreat (moving away from the risk).

A vitally important matter when considering this option in law, is robust (and legally defensible) assessment of coastal hazard risks. If such a future law envisages the compulsory abandonment of private property, getting the science right, for projecting the likelihood of future events, is critical.

Presently the assessment of coastal hazard risks is prescribed in law under the New Zealand Coastal Policy Statement (NZCPS 2010) Policy 24, Identification of coastal hazards. Once a coastal hazard risk to an area of land is identified, the management of those risks is undertaken through provisions set out in Policy 25 (relating to subdivision, use and development) and Policy 27 (relating to the protection of significant existing development).

Implementing this aspect of the NZCPS has met a few speed bumps along the way. Perhaps the most notable being Kāpiti Coast District Council’s attempt at hazard assessment some years ago, which saw a High Court challenge that resulted in the removal of the newly identified coastal hazard areas from Land Information Memorandum (LIMs) and subsequently, a withdrawal of all coastal hazard provisions which set regulatory rules aligned to them in the proposed district plan.

In the interim judgment on the High Court case (Weir v Kapiti Coast District Council [2013] NZHC 3522), Justice Williams concluded that there was “a good argument” for describing the result of the coastal hazard assessment as the “very worst case scenario” - whereas the law requires a very different assessment from coastal scientists doing this work (emphasis mine);

New Zealand Coastal Policy Statement 2010

Policy 24 Identification of coastal hazards

(1) Identify areas in the coastal environment that are potentially affected by coastal hazards (including tsunami), giving priority to the identification of areas at high risk of being affected.

Hazard risks, over at least 100 years, are to be assessed having regard to:

[matters a-h];

taking into account national guidance and the best available information on the likely effects of climate change on the region or district

Jan Wright, Parliamentary Commissioner for the Environment subsequently investigated the issue of the technical assessment of coastal hazard risks in New Zealand practice. She reported that,

”During this investigation, it has become clear that precaution is being embedded into scientific assessments of coastal hazards, sometimes to an extreme extent.”

“The standard results of running a coastal hazard model should be probability distributions with most likely values and ranges of potential values expressed with a level of confidence”,

And recommended to the Minister of the Environment that;

“In revising central government direction and guidance on sea level rise, specify that ‘best estimates’ with uncertainty ranges for all parameters be used in technical assessments of coastal hazards.”

Unfortunately, neither the Minister nor the industry have taken this advice onboard.

The international advice on the likely effects of climate change, on which all our national guidance is based, is provided by the Intergovernmental Panel on Climate Change (IPCC). It uses scenarios to project future sea level rises, the main climate-related source of coastal hazards. In the most recent IPCC Assessment Report (AR6), Climate Change 2021: The Physical Science Basis it advises policy makers not to use its high scenario (SSP5-8.5) calling it “not likely” and “implausible to unfold” (IPCC, AR6 WG1, Chapter 4, section 4.4.2. p. 13).

Despite this the Ministry for the Environment’s interim updated guidance for local authorities following the publication of AR6, persists in recommending the use of SSP5-8.5 in coastal hazard assessments, explaining;

Should SSP5-8.5 scenario still be used in coastal planning?

The upper-range scenario SSP5-8.5 (and its upper likely range of 8.5 H+) should continue to be used, given we are currently on a similar emissions trajectory, combined with the prospect of runaway polar-ice sheet instabilities and very long response time-lags (multi-decadal to centuries) in sea-level rise. This means impacts from sea-level rise will be distinctly different compared with other climate impacts that are more directly tied to global heating and therefore SSP scenarios (eg, heatwaves, precipitation, wind, etc.). These latter effects are also more responsive to cuts in global emissions and involve relatively short response times (decades), unlike sea-level rise.

That’s half right (in that all IPCC scenarios run on a “similar emissions trajectory” in the near-term) and half wrong - in that “runaway polar ice sheet instabilities” are only projected by modelling using scenarios that are found to be running “too hot” and thus, exaggerate the impacts of global warming. As one of the climate researchers in that article explains;

As more city planners and outside scientists turn to these projections, they should first be sure to consult a climate model expert. “Given that these results guide climate adaptation and investments of billions of dollars, that seems like an effort worth doing,” Knutti says.

We have many outstanding climate experts in New Zealand advising the Minister of Climate Change. However, I worry that much of that advice might support the ‘too hot’ end of the spectrum. The justification for the continued use of the SSP5-8.5 does not express an uncertainty range, or probability related to the “runaway polar ice-sheet” assertion, as was recommended by the Parliamentary Commissioner for the Environment.

NZCPS 2010, Policy 24 - the law in New Zealand on hazard risk assessment - is (to my mind) clear: regulators are to assess the likely (not the unlikely) effects of climate change over at least 100 years. The reason is straightforward, the flipside of the sea level rise risk is that residents unnecessarily have the enjoyment of their property curtailed today based on unlikely events as much as a 100 years away.

Hon James Shaw, Minister of Climate Change was questioned on update of the guidance manual to take into account the recent IPCC AR6 advice on use of the SSP5-8.5 scenario. He responded:

“Understanding the climate risks that we face goes beyond what the “likely” impacts of climate change will be”.

From a planning perspective this concerns me, particularly as we are now moving toward the preparation of adaptation plans and legislation that could introduce regulatory takings associated private property. Adaptation planning is a policy path we must face, but I only ask that we face it with a clear understanding of the likelihood of the events unfolding, as opposed to the “full range of possibilities” (another phrase used in justification by the Minister) with no likelihoods attached.

My point being: it is within the full range of possibilities that I am struck by lightning during my lifetime, but I am not planning for it by never walking in the rain.

*Katharine Moody is a senior tutor at Massey University's College of Humanities and Social Sciences in Palmerston North, who comments on interest.co.nz as "Kate".