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1 Introduction

Key points:

  • The climate is changing. It is internationally accepted that further changes will result from increasing amounts of greenhouse gases in the atmosphere. Climate change effects over the next decades are predictable with some level of certainty, and will vary from place to place throughout New Zealand.

  • The climate will also change from year to year and decade to decade owing to natural processes. For example, some parts of the country often have dry summers and autumns when an El Niño climate pattern is present. Both natural fluctuations and human-induced climate changes need to be considered when developing adaptation plans and policies.

  • 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 regulatory, assessment and planning activities. It is not necessary to develop a whole new set of procedures for dealing separately with effects and impacts of climate change. Rather, they can be built into existing practices.

  • Responding to climate change is an iterative process. It will involve keeping up-to-date with new information, monitoring changes and reviewing the effectiveness of responses.

1.1 Local government and climate change

Climate change effects due to the increase in greenhouse gases in the atmosphere will be felt over time at regional and local levels, differently in various parts of New Zealand.

In the last two decades, there has been a rapid growth in understanding of both the cause and impacts of climate change due to human-induced greenhouse gas emissions. Local authorities need to keep aware of these changes so that they can plan adequately for their own communities’ needs, and avoid liability for decisions where climate change may result in subsequent costs in the private sector.

Local government has a range of functions and responsibilities relating to managing climate change effects under the Local Government Act 2002, the Resource Management Act 1991 and its subsequent amendment, and other legislation. These may include, for regional councils: management of water resources, air resources and land resources where there are regionally significant management issues, 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. As well as having an overall planning and management role, regional and district councils own community assets (such as stormwater systems, water supply, or council-owned roads and bridges) that may be vulnerable to climate change effects.

Local government already addresses many effects of extreme weather and climate variations. This Guidance Manual outlines how climate change effects can be addressed as part of these existing regulatory, assessment and planning activities. Early planning may not only prevent a community from being locked into an inflexible response, but may also result in considerable savings if remediation work is avoided.

Many of the effects of climate change will be negative, but some parts of New Zealand will experience changes that, if planned for, can result in positive outcomes for areas and communities. Opportunities to benefit from aspects of climate change, such as the increased temperatures that some areas will experience, will be maximised if councils identify and plan for such benefits in advance. Integrated planning may well be needed as, for example, opportunities to grow new types of crops may be maximised if a community also plans ahead for the management of its water resources to meet the needs of new crops. However, the availability of water resources themselves may be affected by climate change, which must be taken into account in forward planning.

1.2 Who is the Guidance Manual for?

Everyone has a stake in climate change. However, this Guidance Manual is particularly directed at people who advise local government decision-makers. These are most likely to be:

  • strategic and policy planners who need to evaluate and advise on long-term strategies and policy for the district and region

  • asset managers charged with planning future asset needs for communities and solving existing and emerging problems

  • engineers charged with designing infrastructure that is adapted to meet foreseeable risks

  • people handling resource, and in some cases, building consent applications

  • people responsible for council databases, particularly those that provide information on hazards and risks to private landowners and other agencies

  • those responsible for emergency management and ‘lifelines’.

Box 1.1: Climate change complexity

It is tempting to consign climate change to the ‘too hard basket’. The message of this Guidance Manual is that the issues can be broken down into manageable parts, and dealt with as part of normal council planning and management activities. The approach for considering climate change effects on a particular council function or asset (eg, stormwater drainage systems) is illustrated in Figure R1, and includes the following common-sense steps:

  • Consider whether the particular function or service is important to your council and influenced by climate, so you can prioritise action.

  • Pay particular attention to long-lived infrastructure and developments that will need to cope with climate conditions in 50 to 100 years’ time.

  • Start with an initial ‘screening’ assessment, using simple estimates of how climate factors relevant to a particular function may change, and expert judgement or simple calculations of likely impacts of these changes.

  • It is necessary to embark on a more detailed study of climate change effects on the function or activity, utilising more staff or consultant time, only if the screening assessment indicates possible problems or opportunities.

There are increasingly robust findings about the directions climate changes will take. This Guidance Manual provides ranges (low and high limits) for the expected magnitudes of many of the most important climate changes. These ranges can be used to develop scenarios for climate impacts. The projected range of impacts can be taken into consideration now, when designing long-lived infrastructure or planning land use. This strategy will often be less expensive and disruptive than trying to remedy ignored problems later. And, it will usually have the added bonus of making the council’s activities and the community more resilient to present climate extremes.

1.3 The IPCC Fourth Assessment, 2007

The Intergovernmental Panel on Climate Change (IPCC) is the body established by the United Nations to organise impartial expert assessments of climate change knowledge.

Approximately once every six years since 1988, it has produced a full assessment of the current state of scientific knowledge on climate change and what it means for us. These reports synthesise evidence and analyses published either in peer-reviewed journals or other credible sources.

The IPCC Fourth Assessment Report1 involved over 1,200 scientific authors and over 2,500 expert reviewers from more than 130 countries. These people are not employed by the IPCC; most work for independent scientific research organisations.

The Fourth Assessment Report broadly supports the direction of the Third Assessment on which the previous edition of this Manual was based. In most areas, however, the scientific conclusions are now more certain.

Nevertheless, there remain uncertainties in predicting the detail of future climate changes and their effects. These uncertainties range from difficulties in predicting future greenhouse gas emissions (which depend on social and economic development around the world), through to scientific and modelling uncertainties. The approach used to address these global uncertainties is to consider a range of scenarios, which span plausible future emissions and incorporate the uncertainty ranges of the models employed.

The IPCC developed 40 different future emissions pathways or scenarios (referred to as the ‘SRES’ scenarios2), which fall into four families (A1, A2, B1, B2). Each family envisages a different future, with different levels of technological development and global economic integration. While some scenarios are more environmentally sustainable than others, none includes any climate-specific international action, such as the Kyoto Protocol.

There are six SRES ‘illustrative’ scenarios, each broadly representative of its ‘family’3 and spanning a reasonable range of plausible futures. From lowest to highest in terms of temperature projections for this century, they are: B1, A1T, B2, A1B, A2 and A1FI. A more detailed description of these scenarios is contained in Appendix 1.

For the most part, the guidance in this manual takes account of all six SRES ‘illustrative’ scenarios but focuses on the ‘middle-of-the-road’ A1B scenario. The manual also presents results from NIWA regional climate modelling for the B2 and A2 scenarios, which flank the A1B scenario.

1.4 What’s new in this edition

This is the second edition of the Guidance Manual, and it supersedes the first edition published in 2004. The Manual has been updated throughout to incorporate the findings of the IPCC Fourth Assessment Report, with many other ancillary changes. The key differences are:

  • The New Zealand scenarios are completely new, based now on downscaling of simulations from 12 climate models. (The first edition used six models to mid-century, with only four continuing to 2100.)

  • The same statistical downscaling approach is used as previously, but now derived from high-resolution gridded data for temperature and precipitation, instead of from climate stations.

  • Very recent results from NIWA’s regional climate modelling are presented for IPCC emission scenarios A2 and B2. The results allow a more physically based calculation of changes in extremes such as: high and low daily temperatures, snow, winds and heavy rainfall.

  • The adjustment factors for how return periods of heavy rainfall are expected to be affected by global warming (see Table 5.2) have been revised. The adjustments are based on an analysis of rainfall changes simulated by the NIWA regional climate model.

1.5 Reasons for identifying climate change impacts and adapting to them now

Amongst other things, the IPCC Fourth Assessment, 2007 finds:

  • Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.

  • A global assessment of data obtained since 1970 has shown that it is likely that anthropogenic warming has had a discernable influence on many physical and biological systems.

  • 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.

  • Anthropogenic warming and sea-level rise would continue for centuries owing to the time scales associated with climate processes and feedbacks, even if greenhouse gas concentrations were to be stabilised.

Given these findings, the IPCC4 concluded that:

Adaptation will be necessary to address impacts resulting from the warming which is already unavoidable due to past emissions.

It also stated that:

A wide array of adaptation options is available, but more extensive adaptation than is currently occurring is required to reduce vulnerability to future climate change.

The Fourth Assessment Report provides climate projections5 based on scenario analysis for the period 2090–2099 relative to 1980–1999. The projections include:

  • Temperature: The best estimates of global average surface warming are 1.8°C (lowest individual scenario) to 4.0°C warming (highest individual scenario) for the six SRES illustrative scenarios. (The likely6 ranges for these lowest and highest SRES illustrative scenarios are 1.1–2.9°C, and 2.4–6.4°C, respectively.)

  • Rainfall: Increases in annual rainfall are projected for some regions and decreases for others (depending on latitude among other factors). For the A1B scenario, which is one of the ‘middle-of-the-road’ SRES illustrative scenarios, these changes are projected to be up to 20%.

  • Snow cover: It is projected to contract.

  • Sea level: No best estimate or upper bound is provided because of limited understanding of some important effects driving sea level. However, a projected global mean sea-level rise ranging from 0.18 m to 0.59 m, corresponding to the temperature range above, is estimated from models that do not include uncertainties in climate–carbon cycle feedbacks or the full effects of changes in ice sheet flow.

The IPCC also identifies a range of beneficial and adverse effects on both environmental and socioeconomic systems. It concludes that the impacts of climate change will vary regionally but, aggregated and discounted to the present, that they are very likely to impose net annual costs, which will increase over time as global temperatures increase.

Projecting regional and local climate changes across New Zealand from these global projections requires further ‘downscaling’, since the global average does not necessarily apply to a given location in New Zealand. Chapter 2 summarises the region-specific climate projections across New Zealand associated with the IPCC emission scenarios. It explains that as well as uncertainties in global greenhouse gas emissions and concentrations, local and regional uncertainties also arise because of prediction differences between different regional climate models.

Given these uncertainties, it might be tempting to defer any actions to adapt to local climate change, but New Zealand is already experiencing climate changes. These include:

  • increasing temperatures (about 0.9°C over the period 1908–2006)

  • reduced frost frequency over much of the country

  • retreat of South Island glaciers and snowlines

  • reduced alpine snow mass

  • rising sea level (estimated at 0.16 m during the 20th century7).

Natural fluctuations in climate are also experienced from year to year and decade to decade, such as the changes in rainfall, droughts, sea level and coastal erosion associated with El Niño or La Niña conditions described in chapter 3. The recommended approach is to take action now to identify and adapt to the significant effects of both natural climate variations and climate change. As a signatory to the United Nations Framework Convention on Climate Change, New Zealand has commitments to formulate and implement national and regional programmes containing ‘measures to facilitate adequate adaptation to climate change’.8

Despite remaining uncertainties about the magnitude of regional climate changes, certainty is growing as to the direction of expected changes over the coming century. These directions include:

  • increasing temperatures over the whole country

  • increasing annual average rainfall in the west of the country and decreasing annual average rainfall in Northland and many eastern areas

  • reductions in frosts

  • increasing risk of dry periods or droughts in some eastern areas

  • increasing frequency of heavy rainfall events

  • rising sea level.

The robustness of these findings, and the long-term and inexorable nature of climate changes, means that councils and communities do need to consider and plan for climate change. Of particular importance are infrastructure and developments with a long lifetime, which 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. Remedying problems with long-lived infrastructure later on is often going to be more expensive and disruptive to communities than taking future changes into account at the planning and design stage.

1.6 Methods

Risk assessment is central to the approach promoted in this Guidance Manual. We draw particularly on AS/NZS4360:2004 (Risk Assessment) (Standards New Zealand 2004), SNZ HB 4360:2000 (Risk Management for Local Government) (Standards New Zealand 2000), and the Ministry of Civil Defence and Emergency Management’s Guidelines for Developing a CDEM Group Plan (Ministry of Civil Defence and Emergency Management 2002). These procedures are already well known within local government, and allow the effects of climate change to be considered as part of existing planning, assessment and regulatory activities.

Because climate change does not occur in isolation, this Guidance Manual strongly advocates to make planning for climate change an integral part of councils’ standard work. Every function or service that relies on, or is affected by, climate parameters such as rainfall, sea level or wind, has potential to be affected by climate change. Standard methods used to consider the effects of climate on a council’s responsibilities generally provide a good platform to consider the effects of climate change as well, and ensure that the consideration of climate change is done efficiently and at least cost while being relevant to the problem in question.

For climate change effects, this Guidance Manual suggests an additional ‘initial screening assessment’ step in standard risk assessment procedures. Screening analysis uses simple initial estimates of how relevant climate factors will change, together with expert judgement or simple calculations of likely impacts of these changes, to test their significance to a council’s activities. This approach can be applied either to one particular issue (such as the impacts of changed heavy rainfalls on stormwater systems), or to prioritising the relative importance of various climate change impacts. Further analysis for climate change is needed only when the screening assessment suggests that there may be a significant issue, and/or that there is clearly inadequate information to make a judgement based on a simple analysis.

A series of ‘real-life’ case studies have been undertaken to showcase good practice in planning for climate change events. Reports from these studies can be found here (3 April 2008).


1  IPCC 2007a, 2007b, 2007c.

2  ‘SRES’ refers to the report, The IPCC Special Report on Emissions Scenarios, in which the scenarios are presented.

3  The reason there are six illustrative scenarios, despite there being only four families, is that the first ‘family’ (A1) is subdivided into three scenario groups (A1T, A1B, A1FI).

4 IPCC 2007b.

5  In IPCC terminology, a climate projection describes a potential future evolution of the climate in response to an emission or concentration scenario of greenhouse gases and aerosols, and is often based on a simulation by a climate model.

6  The ‘likely’ range is the band within which the authors of the Fourth Assessment Report consider there is a greater than 66% likelihood of an outcome or result.

7  Hannah 2004.

8  Article 4.1(b), United Nations Framework Convention on Climate Change.