View all publications

Executive Summary


This document provides guidance on identifying and assessing likely future regional and local effects of climate change across New Zealand. It is designed to help local government identify and quantify opportunities and hazards which climate change poses for their functions, responsibilities and infrastructure.

Climate-related risks are not new to New Zealand local government planners and resource and hazard managers. Climate change will, by and large, not create new risks, but may change the frequency and intensity of existing risks and hazards, as well as introducing some long-term shifts in climate regimes across the country. Adapting to long-term climate change will also contribute to our resilience to natural fluctuations in climate, such as the El Niño which often leads to dry conditions in eastern parts of New Zealand. Planning to address the effects of climate change is most likely to be effective and cost-efficient if it is integrated into local government's standard work programme, rather than treated in isolation.

Local government is responsible for a range of functions which may be affected by climate change, under the Local Government Act 2002, the Resource Management Act 1991, and other legislation. For regional councils these functions may include management of regional water, air and land resources, biosecurity, natural hazards management, emergency management, and regional land transport. For city and district councils they include land-use planning and decision-making, building control, emergency management and provision of infrastructure and community services. Local authorities own community assets which may be vulnerable to climate change effects.

In 2001 the Intergovernmental Panel on Climate Change identified "new and stronger" evidence that most of the warming observed over the past 50 years can be attributed to human activities that have increased greenhouse gas concentrations in the atmosphere. The IPCC concluded that observed changes in regional climate have affected many physical and biological systems, and pointed to preliminary indications that social and economic systems have also been affected. Further climate changes are inevitable, even if co-ordinated international actions are taken to reduce emissions, because of the inertia in the climate, economic and social systems.

Councils and communities should therefore be giving serious consideration to the potential future impacts of climate change on their functions and services. Of particular importance are infrastructure and developments that will need to cope with climate conditions in 50 to 100 years' time. Examples include stormwater drainage systems, planning for irrigation schemes, development of low-lying land already subject to flood risk, and housing and infrastructure along already eroding coastlines. Climate change may also bring opportunities, for example for growing new horticultural crops in a particular area, to which councils may wish to pay attention.

Guidance Manual contents and use

This Guidance Manual provides projections of future climate change around New Zealand, and information on how these compare with present climate extremes and variations. It identifies potential effects on local government functions and services, and outlines methods for assessing the likely magnitude of such effects. The note then explains how this information can be applied to assess the risk associated with various climate change impacts, and provides guidance on incorporating climate risk assessment into local government regulatory, assessment and planning processes.

Most users of this Guidance Manual will not wish to read it from cover to cover, but will concentrate on the parts which help them deliver on their own responsibilities. To help users find the information relevant to their needs, Chapter 1 provides some "roadmaps" which set out the steps involved in typical assessments and show where to find key guidance for these steps. Chapter 1 also summarises key issues for councils and begins to outline approaches to be taken for identifying effects and adapting to changes. An incremental approach to risk assessment is recommended, beginning with an initial screening assessment. This uses simple initial estimates of how relevant climate factors may change, together with expert judgement or simple calculations of likely impacts of these changes, to test the significance of the changes for a council's activities. Further detailed analyses are only justified if these screening studies suggest a material impact is possible. This screening approach can be applied to a particular function, asset or activity, or it can be applied right across a council's activities.

Councils already address extreme weather events and climate variations as they develop plans and provide services. It makes good sense to consider climate change effects as part of these existing regulatory, assessment and planning activities. It is not necessary or even advisable to develop a whole new set of procedures for dealing separately with impacts of climate change, but it is vital to integrate climate change into standard considerations to ensure council activities are "future-proofed" and remain sustainable for future generations.

The contents of individual chapters of the Guidance Manual are now outlined:

Projections of future New Zealand climate change (Chapter 2)

The Intergovernmental Panel on Climate Change in its Third Assessment Report (2001) projects a global temperature increase of between 1.4°C and 5.8°C by 2100. Chapter 2 summarises results from "downscaling" these global projections to New Zealand. Temperature changes here are expected to be less than the global average, as a result of a lag in warming of the oceans surrounding New Zealand. Tables in Chapter 2 and Appendix 3 break down these projected changes by regional council area and provide quantitative estimates along with the range of uncertainties. The broad expected pattern of change is:

  • increased temperatures (with greater increases in the winter season, and in the north of New Zealand)
  • decreased frost risk but increased risk of very high temperatures
  • stronger west-east rainfall gradient (wetter in the west and drier in the east)
  • increased frequency of extreme (heavy) daily rainfalls
  • increased sea level
  • increased westerly winds.

Projected New Zealand changes cover a wide range, reflecting the diverse range of greenhouse gas emission scenarios used by the IPCC and also climate model uncertainties. Mid-range projections in annual-average temperature and precipitation are:

  • temperature increase of 0.6 to 0.7°C from 1990 to 2030s (45-year change), and 1.6 to 2.0°C from 1990 to 2080s (95-year change)
  • rainfall change between about -5 to +5% from 1990 to 2030s, and about -10 to +15% from 1990 to 2080s (the sign and amount varies around the country).

The projected range of possible sea level changes around New Zealand by 2100, corresponding to the full IPCC global temperature projection range, is 9-88 cm.

Relationship to current climate change and variability (Chapter 3)

New Zealand climate varies naturally from year to year and from decade to decade. In individual years, annual New Zealand-wide temperatures can deviate from the long-term average by up to 1°C (plus or minus), whereas regional precipitation can deviate by about 20% (plus or minus). The sign of the deviation will depend on whether it is a La Niña or El Niño year, and will also depend (for precipitation) on geographic location. (Details can also vary a lot from event to event.) New Zealand also experiences decadal climate variations, related to a Pacific-wide natural feature called the Interdecadal Pacific Oscillation (IPO). Research is still in progress on how predictable the IPO and its local climatic impacts are. This research suggests we recently moved into a negative IPO phase which could last for the next 20-30 years. This is likely to favour reduced westerlies and southwesterlies, rainfall reductions in the southwest of the country but increases in the northeast, and an increased rate of air temperature and sea-level rise.

These natural variations will continue to impact New Zealand climate through this century, and will be superimposed on the human-induced long-term climate change trend. This combination of underlying mean climate (with appropriate global warming adjustments) plus natural variations will give us the extremes which future New Zealand society will have to adapt to.

The sizes of current natural perturbations of the climate about the long-term mean are comparable to the mid-range projected human-induced changes we might expect over 30-50 years. This means that what currently is an unusually warm year could be the norm in 30-50 years, while an unusually warm year in 30-50 years' time is very likely be warmer than anything we experience at present.

Effects on local government functions and services (Chapter 4)

Studies already carried out in New Zealand show that climate changes of the magnitude projected in this report for the 2030s and 2080s could have significant effects on various council functions and activities. These effects will often be different in different parts of the country, and may be negative, positive or mixed. For example, increasing temperatures may make some parts of the South Island more suitable for horticultural development, which in turn may place increasing demands on water for irrigation. The availability of water for irrigation may itself be affected by climate changes.

The range of local and regional functions, services and activities on which climate change could potentially impact (Table 4.1) is wide, including strategic and land use planning, water supply and irrigation, stormwater and flood management, roading, coastal infrastructure, management of terrestrial and aquatic ecosystems, civil defence and emergency management, and biosecurity. Chapter 4 provides information and guidance that will help individual councils identify which of their functions will be materially affected. It summarises data, sources of information, models, and specialist expertise available in New Zealand. It also provides some examples of work that some local authorities have already undertaken.

Developing scenarios for use in effects assessment (Chapter 5)

A definitive quantitative prediction of exactly how much a particular climatic element (e.g. heavy rainfall intensity) will change over coming decades is not feasible. This is because rates of climate change will depend on future global emissions of greenhouse gases, which in turn depend on global social, economic and environmental policies and development. Incomplete scientific knowledge about some of the processes governing the climate, and natural year to year variability, also contribute to future uncertainty.

This leads to "scenario analysis" as an appropriate tool for assessing likely effects of climate change. Climate, social and economic scenarios are formulated which span the likely range of future conditions. These are used together with expert knowledge and models of the sensitivity of natural or managed systems to climate, to deduce a range of possible climate impacts on selected council activities and functions.

The first recommended step is an initial screening assessment for a particular council function, activity or asset. This uses simple initial estimates of how much relevant climate factors may change (usually either a single mid-range value, or a plausible upper and lower end of the scale), together with expert judgement or simple calculations of likely impacts. Further detailed analyses are only justified if the screening assessment suggest a material impact on the activity or service is possible, for at least the upper end of the scale of potential future changes.

Chapter 5 provides guidance on undertaking scenario analyses, including tables of values and sources of climatic information for use in both screening and more detailed studies. Examples are provided covering water resources (Southland), changes in agricultural water usage and resources in three river catchments (Rangitata, Motueka and Tukituki), and effects on stormwater and wastewater systems (North Shore City).

Risk assessment (Chapter 6)

Local government organisations have to make long-term decisions for the community, including decisions on asset management and planning. Resources are often limited, and priorities must be set for where to apply them. Risk assessment methodology provides a systematic process for identifying risks associated with climate change, comparing them against other risks, prioritising them, and developing adaptation plans or making specific decisions. Chapter 6 describes the overall risk assessment process in the context of climate change, outlining methods which are already familiar to most local authorities, with the addition of a screening level assessment for an issue first to indicate whether a full risk assessment is warranted.

Integrating climate change risk assessment into council decisions (Chapter 7)

Chapter 7 describes how to incorporate knowledge about climate change risks and opportunities into council planning. Key principles for local government to keep in mind when dealing with climate change effects include: sustainability; the needs of future generations; avoidance and mitigation of adverse effects; a cautious or precautionary approach; prudent stewardship and kaitiakitanga; consultation; financial responsibility and liability.

Case law which has developed to date, particularly through the Resource Management Act, covers the following issues of relevance to local authorities:

  • recognising the reality of climate change
  • clarifying the respective roles of regional and territorial authorities
  • indicating principles of hazard avoidance
  • indicating time scales over which to consider effects
  • clarifying the relationship between resource and building consents.

Chapter 7 describes the relevance of climate change to local government management and planning responsibilities, and discusses existing use rights, resource consent decisions, and building consents. It recommends long term monitoring of climate change and its effects, as a basis for ongoing adaptation to change. A checklist is provided (Appendix 5) for addressing climate change in plans developed under the Local Government Act 2002, the Resource Management Act 1991, the Civil Defence and Emergency Management Act 2002, and other legislation.

This final chapter is particularly important, since the Guidance Manual will only have succeeded if councils build consideration of climate change effects into policy development and decision-making for relevant functions and services.