View all publications

Executive summary

This Guidance Manual is designed to help local governments identify and quantify opportunities and hazards that climate change poses for their functions, responsibilities and infrastructure. This is the second edition of the Guidance Manual, and it supersedes the first edition published in 2004. It follows the updated assessment of the science of climate change produced by the Intergovernmental Panel on Climate Change (IPCC) in its Fourth Assessment in 2007.

Why plan now for climate change?

Climate-related risks are not new to New Zealand local government planners, or 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 contribute to our resilience to natural fluctuations in climate, such as El Niño, which often leads to dry conditions in northern and 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 standard work programmes, rather than done in isolation.

Local government is responsible for a range of functions that 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 that may be vulnerable to climate change effects.

In 2007, the IPCC concluded that most of the observed increase in global average temperatures since the mid-20th century is very likely a result of the observed increase in anthropogenic greenhouse gas concentrations. The panel’s assessment of data collected since 1970 showed it is likely that anthropogenic warming has had a discernable influence on many physical and biological systems. It concluded that the continued emission of greenhouse gases at or above current rates would cause further warming and induce many changes in the global climate system during the 21st century, that would very likely be larger than those observed during the 20th century.

Thus, councils and communities should be giving serious consideration to the potential future impacts of climate change on their functions and services. Particularly important are infrastructure and developments that will need to cope with climate conditions in 50–100 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 (eg, 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

  • compares these projections with present climate extremes and variations

  • identifies potential effects on local government functions and services

  • outlines methods for assessing the likely magnitude of such effects

  • explains how this information can be applied to assess the risk associated with various climate change impacts

  • provides guidance on incorporating climate risk assessment into local government regulatory, assessment and planning processes.

Most users of this Guidance Manual will concentrate on the parts that help them fulfil their own responsibilities. To help users find the information relevant to their needs, the manual provides two ‘roadmaps’ (pages xvii–xviii), that set out the steps involved in typical assessments and show where to find key guidance for these steps.

Introduction (Chapter 1):

How to make assessing climate change manageable

Chapter 1 summarises key issues for councils and outlines approaches to identifying effects and adapting to changes. An incremental approach to risk assessment is recommended, which should begin with an initial screening assessment. This assessment uses simple initial estimates of how the relevant climate factors may change, 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 justified only 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 across all of a council’s activities.

Councils already address extreme weather events and climate variations as they develop plans and provide services. Climate change effects should be considered 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 the impacts of climate change, but it is vital to integrate climate change into standard considerations to ensure that council activities are ‘future-proofed’ and remain sustainable for future generations.

Projections of Future New Zealand climate change (Chapter 2):

New projections based on the IPCC Fourth Assessment, 2007

Projected changes in New Zealand’s climate are given for six scenarios of greenhouse gas emissions. Changes are specified for 2040 (actually the 2030–2049 average), and for 2090 (the 2080–2099 average), relative to the climate of 1990 (1980–1999 average). Most of this information is derived from statistical downscaling of output from 12 global climate models, and is supplemented by initial analyses from two simulations using NIWA’s regional climate model.

New Zealand temperatures are expected to increase by about 1°C by 2040, and 2°C by 2090. However, there is a wide range in the projected future warming owing to the different emission scenarios and differences in climate model sensitivities.

Projected changes in mean rainfall and wind patterns show a more marked seasonality than was evident in models from the IPCC Third Assessment, 2001. The latest results suggest increased westerlies in winter and spring, along with more rainfall in the west of the North and the South Islands and drier conditions in the east and north. Conversely, in summer and autumn, the models suggest decreased frequency of westerly conditions, with drier conditions in the west of the North Island and possible rainfall increases in Gisborne and Hawke’s Bay.

Other changes expected are: decreased frost risk, increased incidence of high temperatures, increased frequency of extreme daily rainfalls, a possible increase in strong winds, and decreases in average snow cover.

Relationship to Current Climate Variability and Change (Chapter 3):

Natural variations will be superimposed on a long-term warming trend, and together they will create extremes

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). Whether the deviation will be above or below the average will depend on whether it is a La Niña or an El Niño year, and will also depend (for precipitation) on geographic location.

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 the predictability of the IPO and its local climatic impacts. There was a shift to the ‘negative phase’ of the IPO around 1999, so more La Niña (and less El Niño) activity may be expected compared to 1978–1998, with a period of higher temperatures for New Zealand. This is likely to favour reduced westerlies and southwesterlies, rainfall reductions in the southwest of the country but increases in the northeast, and faster rises in air temperature and sea level. These conditions could last for the next 20–30 years.

These natural variations will be superimposed on human-induced long-term climate changes, and together they will give us the extremes to which future New Zealand society will have to adapt. 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 to be warmer than anything we experience at present.

Effects on Local Government Functions and Services (Chapter 4):

How to identify what will be materially affected

Climate changes of the magnitude projected in this report 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 impact is wide. It includes 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 are likely to 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 the Scenarios (Chapter 5):

Tools for initial screening and more detailed studies

A definitive single quantitative prediction of how much a particular climatic element (eg, heavy rainfall intensity) will change over coming decades is not feasible. This is because the rate 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 uncertainty in projections for the future.

Consequently, ‘scenario analysis’ is one of the most appropriate tools for assessing the likely effects of climate change. Climate, social and economic scenarios are formulated that span the likely range of future conditions. These are used in conjunction 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.

Chapter 5 provides guidance on undertaking scenario analyses, including tables of values and sources of climatic information for use in both initial screening assessments 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):

Factor in the evolution of climate-related risk over time

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 procedure in the context of climate change, outlining methods that are already familiar to most local authorities, with the addition of an initial screening-level assessment for an issue to determine whether a full risk assessment is warranted.

Integrating Climate Change Risk Assessment into Council Decisions (Chapter 7):

Legal requirements

Key principles for local government to keep in mind when dealing with climate change effects include: sustainability, provision for the needs of future generations, avoidance and mitigation of adverse effects, adoption of a cautious or precautionary approach, prudent stewardship and kaitiakitanga, consultation, financial responsibility and liability.

Case law that has developed to date, particularly through the Resource Management Act 1991, 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.