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Preparing for climate change: A guide for local government in New Zealand

Introduction

Preparing for Climate Change is a guide to help councils across New Zealand assess the likely effects of projected climate change during the 21st century and plan appropriate responses where necessary. It is designed to summarise the main elements of a comprehensive technical report Climate Change Effects and Impacts Assessment ('the source report') which is available in full at: http://www.climatechange.govt.nz/publications/climate/guidance.html.

Some climate changes are occurring now. Future changes are inevitable. While greenhouse gas emission reductions both globally and locally can help slow the rate of climate change, it cannot be prevented entirely. Changes in a number of key climate parameters, such as temperature, rainfall and sea levels, will occur to differing extents in different parts of New Zealand throughout the 21st century and possibly beyond.

If adequately planned for, some of the effects of climate change will be positive. For example, increased temperatures may allow new types of crops to be grown. However, these benefits may be eroded or reversed if climate changes also bring negative effects such as prolonged drought, increased flood risk, or greater frequency and intensity of storms. In any case, informed and proactive planning now can help maximise benefits and minimise the direct and indirect costs of climate change.

Local government is responsible for a range of functions that may be affected by climate including natural hazards and resource management, land-use planning, building control, and the provision of infrastructure such as stormwater drainage and water supply.

Climate-related risks are not new to local government planners, resource managers and emergency and hazard managers. Generally speaking, climate change is not expected to create new risks, but it may change the frequency and intensity of existing risks and hazards, as well as introduce long-term shifts in climate patterns.

Local authorities have both social and legal obligations to take climate change effects into account in their decision-making. This guide explains these obligations, including those under the Resource Management (Energy and Climate Change) Amendment Act, which came into effect on 2 March 2004.

A key message in the guide is that climate change effects can be broken down into manageable parts and dealt with as part of existing council planning and operational processes. Managing climate change effects does not necessarily require new and additional resources. The guide suggests how councils can carry out simple checks to assess whether climate change effects are likely to be significant for a plan, project or activity. If so, more detailed assessments are recommended. Guidance is provided as to how councils might undertake these.

Although the guide will help councils identify, scope and respond to climate change in their areas, it does not provide standard solutions for specific situations. Each region, district and community will have its own climate-related vulnerabilities and priorities.

The guide does, however, provide some specific tools to help councils identify and respond to climate change impacts including a decision-making framework, case studies and practical checklists.

The guide comprises three distinct parts:

Part One explains the general effects of projected global warming on New Zealand, current climate variability, projected future climate changes both nationally and regionally, and how climate change may change the frequency and intensity of extreme weather events such as floods and storms.

Part Two explains councils' social and legal obligations to take climate change effects into account in their community planning, the key principles that need to be considered in responding to climate change, and how to assess the impact of climate change on council functions. Checklists are provided to help ensure that climate change is considered in various plans.

Part Three outlines how councils can integrate climate change into council decision-making, and qualitatively and, if necessary, quantitatively, assess if/how climate change will affect specific council functions and services.

Part One: Current and future climate

This section covers:

• the general impact of climate change on New Zealand
• the current variability of New Zealand's climate
• projected climate change effects at national level and, where possible, at a regional level
• possible changes in the intensity of extreme weather events such as floods and storms
• the significance of climate change versus natural climate variability.

Climate change impacts

Average global temperatures are projected to increase by between 1.4 and 5.8°C by 2100 if no steps are taken globally to reduce greenhouse gas emissions. The increase is expected to be less in New Zealand than the global average because of delayed warming of the oceans surrounding New Zealand.

Mid-range projections for New Zealand are for an increase in the annual average temperature of 0.6 to 0.7°C from 1990 to the 2030s, and 1.6 to 2.0°C from 1990 to the 2080s. There are likely to be greater increases in winter (meaning that the difference between winter and summer temperatures is expected to decrease) and in the north of the country (meaning the difference in temperature between the north and south is expected to increase).

Mid-range rainfall projections for New Zealand as a whole for the same periods are -5 to +5% and -10 to +15% respectively. Generally, a trend to drier conditions in eastern regions and wetter conditions in the west is expected (meaning that the difference in rainfall between western and eastern regions is likely to further increase).

These and other climate changes are likely to lead to both more floods and more droughts in some parts of the country.

Climate change projections also include:

• fewer frosts
• more episodes of high temperature
• increased frequency of heavy rainfall
• an increase in average sea level.

Current climate variability

New Zealand's climate varies substantially from year to year and from decade to decade, with much of the variation apparently random. Some variations, however, have cyclical elements as shown in Figure 1 below.

Figure 1 shows that, in individual years, annual New Zealand-wide temperatures can deviate from the long-term average by up to 1°C (plus or minus). It also shows that, despite these fluctuations, there has been a long-term increase of about 0.6°C between 1920 and 2000. Annual rainfall, too, can deviate from its long-term average, by about plus or minus 20%. Sea levels have risen by an average of 16 cm between 1900 and 2000, with similar plus or minus 20% year-to-year variations.

Some of the shortest-term temperature fluctuations arise simply because of the natural variability in the weather and its random fluctuations or 'chaos'. However, other changes are associated with large-scale climate patterns over the Southern Hemisphere or the Pacific Ocean. There are a number of key natural processes that operate over timescales of seasons to decades, particularly the El Niño-Southern Oscillation (ENSO) and the Interdecadal Pacific Oscillation (IPO).

The ENSO is a tropical, Pacific-wide oscillation that affects pressure, winds, sea-surface temperature (SST) and rainfall. In the El Niño phase, New Zealand usually experiences stronger than normal south-westerly airflow. This generally results in lower seasonal temperatures nationally with drier conditions in the north-east of the country. The La Niña phase is essentially the opposite, usually creating more north-easterly flows, higher temperatures, and wetter conditions in the north and east of the North Island. Atmospheric pressures in the La Niña phase tend to be higher than normal over the South Island which can lead to lower rainfall and, in turn, drought conditions in the north-east of the South Island. Drought can, therefore, occur in New Zealand in both El Niño and La Niña phases. Because the tropical Pacific SST anomalies persist for up to a year, there is substantial predictability in how ENSO oscillations affect New Zealand's climate. The ENSO cycle varies between about three and seven years with large variability in the intensity of individual oscillations.

The IPO is another, recently identified, source of natural variability in climate. It has cycles that can last over several decades. Three phases of the IPO have been identified during the 20th century: a positive phase (1922-44), a negative phase (1946-77) and another positive phase (1978-98). Looking at the climate in these periods can give some guidance on future climate in the short-term. In a positive phase, SST's around New Zealand tend to be lower and westerly or south-westerly winds stronger. Temperatures in all regions are lower. In the negative phase, airflows from the east and north-east were observed to increase, as did temperatures in all regions. Conditions became wetter in the north of the North Island, particularly in autumn, and drier in the south-east of the South Island, particularly in summer. The increase in New Zealand temperatures around 1950 (see Figure 1) coincides with the change from positive to negative phase IPO at that time. Sea levels around New Zealand are also affected by the IPO. Particularly large increases in sea level have been associated with IPO transitions from the positive to the negative phase.

Natural climate patterns such as the IPO can, therefore, act either to suppress or enhance the effects of climate change over periods of up to two or three decades.

At this stage, it is uncertain to what extent the IPO can be accurately used to predict climate phases or patterns in future decades. More frequent natural climate variations, such as the ENSO, are also difficult to predict very far in advance. For this reason, it is not feasible to project natural variations over the next century. However, analysis of the latest sea temperature data suggests that another negative IPO phase may currently prevail. In this case, more La Niña (and less El Niño) activity could be expected, compared to the 1978-98 period, together with a period of higher temperatures. Weaker westerlies are also likely which goes against the observed trend of increasing westerlies.

Future climate

Predictions of future climate depend on projections of future concentrations of greenhouse gases and aerosols, as well as model assessments of how the global climate system will respond to these changing concentrations. Future greenhouse gas concentrations depend on projections of emissions, which depend in turn on national and international policies, and changes in population, economic growth, technology and energy availability.

The source report on which this guide was based provides technical detail about how the New Zealand projections were developed. The maps below show mid-range projections for temperature and precipitation, each averaged for winter and summer.

Expected climate change in New Zealand

Table 1: Main features of New Zealand climate change projections for 2030s and 2080s

Table 1 qualitatively summarises the main features of New Zealand climate projections and contains the best current scientific estimate of the direction and magnitude of change. The level of confidence in the projections is indicated in brackets (VH = very high, H = high, M = medium, L = low). A higher degree of caution should be employed where investment decisions are based on the 'low' confidence estimates. The figures provided are mid-range, based on a range of climate models and greenhouse gas emission scenarios. For planning purposes, councils should consider the full range of scenarios provided in the source report on which this guide was based. Changes in the return period of heavy rainfall events may vary between different parts of the country and will also depend on the rainfall duration being considered (see Section 2.2.4 of the source report for more detail).

Projected changes by region

Tables 2 and 3 on the next two pages show the projected changes for specific locations, based on the full range of IPCC emission scenarios and using a range of global climate models (see pages 11 and 12 of the source report for more details). To help manage the uncertainty represented by the wide spread of data in many instances, councils may wish to consider the maps in Figure 3 on pages 9 and 10 to identify gradients within a region and to get a sense of mid-range trends for a specific location.

Table 2: Projected changes for each regional council area in seasonal and annual average temperature (in °C)

View projected changes for each regional council area in seasonal and annual average temperature (in °C) (large table)

Table 3: Projected changes (in %) in seasonal and annual precipitation by region (based on selected rainfall stations)

View projected changes (in %) in seasonal and annual precipitation by region (based on selected rainfall stations) (large table)

Extreme weather events

The natural variations described earlier will continue to impact on New Zealand climate in the future and will be superimposed on human-induced long-term climate change trends. Climate change is expected to shift the range of variability and in some instances to alter the patterns of variability. It will not remove this natural variability. Thus, the effects of climate change may be felt both through changes in long-term averages and in terms of the changed frequency and intensity of extreme events (such as heavy rainfall, storm surges, drought, or very high temperatures). It is this combination of underlying mean climate, appropriate global warming adjustments, and natural variations that will provide the extremes that future New Zealand society faces. In many instances, it is the extreme events that cause damage and proactive adaptation requires more conscious action. A small shift in the average climate can cause significant changes in the occurrence of extremes.

A change in extremes of particular importance for local government planning is an increase in the risk of heavy rainfall events. Such an increase is likely to be greatest where mean rainfall increases, but heavy rainfall may increase even in areas where the mean rainfall is projected to decrease.

Significance of climate change versus natural climate variability

Historical records show the national-average temperature can vary by up to about 1°C from year to year, and more than this on a seasonal timescale. Thus, the warmest individual years in the current climate have temperatures lying near the upper end of the projected average (climatological) warming for the 2030s. A current extremely hot year may be the norm by 2030 and a hot year in 2030 is likely to be outside the range of what is experienced today. Projected temperatures for the mid-to-high range of the 2080s are well outside the values experienced by New Zealand in the 20th century. A hot year in 2080 will be more extreme still. Likewise, the mid-range projected rise in sea levels of 30-50 cm by 2100 is higher than any year-to-year variations at present.

Similar comparisons can be made for rainfall, but with opposite trends expected for different parts of the country. Seasonal anomalies today seem comparable to the projected average ranges for 2030. Areas that currently have water management issues could see present extremes (eg, water shortages) become the norm by the 2030s depending on the direction of projected rainfall change for their region, and which emissions scenario and model simulation turns out to be the closest to reality. This will be particularly relevant for drought management in eastern New Zealand.

Further details of the estimated changes in both the average and extremes for each major climate parameter are available on pages 18-26 of the source report.

Part Two - Local government and climate change

This section covers:

• an explanation of the social and legal obligations councils to take climate change effects into account in community planning
• key principles that need to be considered in responding to climate change
• a checklist for considering climate change in plans
• how to assess the impact of climate change on council functions.

Climate-related risk and local government

Local authorities are responsible for a range of functions that may be affected by climate. Climate-related risks are not new to New Zealand local government planners, resource managers, and hazard and emergency managers. The effects of floods, droughts, windstorms and other extreme weather events are already addressed by local government when planning and providing services.

Climate change will not generally create new climate-related risks but it may change the frequency and intensity of existing risks and hazards, as well as introduce some long-term shifts in climate patterns across the country. Managing it will not require a materially different approach to managing natural climate variability.

Local authorities have both social and legal obligations to take climate change effects into account in their community planning. Long-term planning functions therefore need to take account of expected long-term shifts and changes in climate extremes and patterns to ensure future generations are adequately prepared for future climate conditions.

The Resource Management (Energy and Climate Change) Amendment Act that took effect in March 2004 directs councils to "have particular regard to the effects of climate change" when making decisions under the RMA (See: http://www.mfe.govt.nz/laws/rma/energy-climate.html).

Key principles for responding to climate change

Local government is required to operate under a range of principles that are set out in law or have evolved through good practice and case law. Many of those principles are relevant when considering the possible effects of climate change.

The key principles are:

• sustainability
• consideration of the reasonable foreseeable needs of future generations
• avoidance, remedy and mitigation of adverse effects
• adoption of a precautionary/cautious approach
• the ethic of stewardship/prudent stewardship/kaitiakitanga
• consultation and participation
• financial responsibility
• liability.

Sustainability

The concepts of sustainable development under the Local Government Act 2002 and sustainable management of an area's natural and physical resources under the Resource Management Act 1991 (RMA) imply the ongoing ability of communities and people to respond and adapt to change in a way that avoids or limits adverse consequences. In recent years the causes of climate change have been tackled at an international level, while local communities have been encouraged to adopt no- or low-regrets responses to climate change. These responses fit within the concept of sustainability. They involve applying adaptive, and sometimes limiting, responses that will not be regretted, irrespective of the eventual nature and magnitude of climate change effects. Examples are a range of energy efficiency and conservation practices, forest planting, and avoidance of new development in areas already or potentially hazard prone. More recent understanding of climate change has meant a shift to risk-based assessments of its effects and responses by local authorities, prior to decisions being made in the interests of long-term sustainability.

Consideration of the foreseeable needs of future generations

This concept, contained in both the Local Government Act and the RMA, is at the heart of international, national, regional and local responses to climate change. It involves taking into account the interests of future generations, and the direct and indirect costs they may bear, as a result of decisions made today i.e. responsible action in the context of balancing the needs of the present with those of the future. The principle applies even where the need for a climate change response is not yet apparent.

Avoidance, remedy and mitigation of adverse effects

Avoidance, remedy and mitigation of adverse effects under the RMA applies to the preparation of plans by local authorities under that Act, every decision made under that Act, and everyone who carries out an activity or development under the Act. 'Effect' includes temporary or permanent effects, present and future effects, cumulative effects over time, and potential effects of high probability, or of low probability with high potential effects. This means that, through reasonable understanding and analysis of future environmental change, climate change impacts can and should be taken into account when contemplating new activities and developments, since climate change can affect the ability of ecosystems and communities to cope with other non-climatic pressures.

Adoption of a precautionary/cautious approach

This concept is implied in the RMA and in the New Zealand Coastal Policy Statement prepared under that Act, and is directly stated in the Civil Defence Emergency Management Act 2002. It requires an informed but cautious approach to decisions where full information on effects is not available, particularly when there is a high level of uncertainty and where decisions are effectively irreversible. A precautionary approach is also relevant where there are effects of low probability but high potential impact, such as the effects of infrequent but high flood levels in developed flood plain areas. An analysis of plans to consider the risks of 'acting or not acting' in a situation where the adequacy of information is uncertain is provided for under the Resource Management Amendment Act 2003. This is of direct relevance to addressing climate change effects in plans, as well as other situations where a cautious approach may be appropriate.

The ethic of stewardship/prudent stewardship/kaitiakitanga

The Local Government Act and the RMA both contain these concepts. In the Local Government Act, prudent stewardship is to be applied to the efficient and effective use of a community's resources in the interests of the district and region. In the Resource Management Act, the ethic is applied to the wider environment. The principle underpins sound planning decision-making in the interests of the community to avoid or minimise loss of value or quality over time. Its relevance to climate change relates particularly to asset management, land and water care, biosecurity and biodiversity.

Consultation and participation

Principles of consultation with communities and affected people are fundamental to local government decision-making. Consultation implies informed input into decision-making processes. For decisions likely to be influenced by climate change, those being consulted must have sufficient information to understand the likely scenarios and associated risks for their communities. Ensuring adequate information is available within a community for consultation processes to be effective is a responsibility for regional and local government, and will involve the translation of international and national knowledge to local levels, with indications of degree of certainty and uncertainty. Consultation and participation can also be used to raise awareness of risk and appropriate responses e.g. flood risk and how the costs and benefits of flood mitigation efforts should be shared within the community.

Financial responsibility

Local government is expected to act within normal codes of financial responsibility on behalf of the community. In undertaking its own activities, particularly asset provision and management, the Local Government Act sets out requirements to identify in detail the reasons for any changes to current provision, and the cost. For infrastructure enhancements due to future effects of climate change, both evaluation of risks and the costs of different levels of service will need to be expressed in a transparent manner.

Liability

Local government can be financially liable for decisions made despite information that should have led to another decision. This is a difficult area of law, and councils use a range of techniques to reduce the risk of liability. For example, where single property-based decisions are involved, instruments such as covenants or consent notices attached to titles may be used to identify risks. Larger climate-related issues, such as frequency of flooding of a developed area, are less likely to result in direct liability unless areas become uninhabitable as a result. However, community costs in enhancing or retrofitting infrastructure can become considerable. Questions of equity in relation to wider community interests also arise.

Checklists for considering climate change in plans

The checklists below are designed to assist councils to take these principles into account when considering climate change effects in plan development and review.

View checklist for considering climate change effects in plans (large table)

Assessing the impact of climate change on council functions

A number of council functions, services and activities can be affected by climate change. Key factors to take into account when assessing whether climate change is likely to have a critical impact on a particular function or activity include:

Duration of issue being addressed

Consider the period over which the decision will have effect. Generally, climate change should be considered if the effects of the decision will last 30 years or more. Local government decisions have a range of implications in terms of time horizons. For example:

• Approval for a new development area or a coastal reclamation is effectively permanent.
• A building consent assumes new structures have a life of 50 years but many structures are intended to, or do, last much longer.
• Infrastructure decisions generally assume a 50 to 80-year life, but some can be designed to be built on a staged basis to provide extra capacity in response to climate change over time.
• Decisions on structures in rivers, most coastal structures, and infrastructure that involves regional council consents, have a term of 35 years or less, but in reality their lifetime may be much longer (e.g. significant bridges) and they should be recognised as near-permanent.
• Decisions on land care, biodiversity and pest management strategies may be in the context of a three, five or 10-year strategy, but some decisions may have enduring consequences so a long-term view may be appropriate.

Presence of a particular 'driver'

Climate change considerations are particularly important when decisions are required on the likes of infrastructure. Any significant investment in infrastructure should always be preceded by a risk assessment that includes climate change implications and a cost-benefit analysis. When climate change is factored in, the resulting asset 'life-cycle' costs should be less than the additional costs from premature retirement of the asset or later unprogrammed upgrades. In some situations, the design of new infrastructure may 'lock in' resource requirements in a way that makes later upgrading virtually impossible.

Decisions on subdivisions and developments are driven by applications in the private sector. Councils must make decisions relatively quickly. Such decisions need to be made in the context of climate change effects possibly exacerbating natural hazards. If a council thinks an application has inadequate consideration of climate change factors and that such factors are relevant, further information should be sought in preference to making a hasty decision.

Location of issue being addressed

Some locations are more vulnerable than others to climate change effects. For example, all proposals near the coast should be evaluated in terms of expected sea-level rise over the next century, as well as other consequential effects such as increased coastal erosion, salt water intrusion into aquifers and increased flooding. Development in flood plains also needs to take account of the potential for reduced flood return periods and potentially greater peaks.

Extent of issue being addressed

Decisions that involve, for example, a single building or a small part of an infrastructure asset (unless the latter constrains the rest of the system) are less likely to have fundamental and long-term implications than decisions that affect larger areas. The exception is where a small development sets a precedent, leading to acceptance of subsequent applications.

Nature of issue being addressed

The risk assessment process should identify whether the issue is affected by a single climate parameter or whether it is a complex issue with multiple effects and implications over time. The latter needs to be addressed at policy level, with decision-making carried through consistently over time. Relatively general information may be adequate to start policy development and information can be refined over time within a generic policy context. For example, in planning an urban extension, if there are options, low-lying coastal areas should be avoided, and if flood plains are being considered, higher and more frequent floods than in the past should be assumed.

Part Three: Responding to the effects of climate change

This section covers:

• integrating climate change into council decision-making
• qualitatively assessing the influence of climate change on council functions and services
• developing quantitative scenarios of likely effects of climate change
• assessing climate change effects using complex scenarios
• using a full risk assessment process for climate change effects.

Integrating climate change in decision-making

Climate change is relevant to a wide range of local government functions and adds to the many uncertainties that councils must consider in all their planning, risk assessment and decision-making. Every council function or service that relies on, or is affected by, climate parameters such as rainfall, sea level or temperature, including evaporation and water demand, can be affected by climate change.

Climate change considerations are unlikely to drive or initiate local government action on their own. Rather, through the application of risk management processes in assessing and prioritising possible responses to the effects of climate change, they may modify an outcome. Many councils have already taken steps towards integrating climate change in plans. Some examples are summarised on pages 15-17.

The emphasis in this part of the guide is on understanding the scope and variation of climate change, deciding on priorities for action, and assessing risk to work out how best to respond based on the level of risk.

Climate change risk assessment is best undertaken as part of ongoing council activities, not as a separate issue. It is not necessary to address the impacts of climate change on all functions and services at once. It is a matter of prioritising i.e. focusing on activities where climate change may have a material effect and may require a response in the near future, undertaking an initial assessment and embarking on more detailed study if this assessment indicates it is warranted.

Generally, councils can use a series of steps of increasing complexity to assess whether climate change is relevant to a particular council function, how significant its impact might be, and the appropriate response.

The first step is to identify qualitatively whether a specific council function or service could be affected by climate change or, more generally, which council functions are vulnerable to climate variability and, therefore, to climate change. If this process identifies a possible climate change effect, an initial quantitative assessment or 'screening' analysis should be undertaken. This consists of using a range of scenarios for climate change and other drivers to test quantitatively the likely significance of climate change, and whether existing planning and management provisions have a sufficient safety margin to cover any resulting change in risk or resource availability.

If it appears that existing provisions do not adequately cover the future change in risk, a more complex scientific and technical risk assessment should be undertaken followed by an analysis of response options to manage the risk over appropriate timeframes.

Because of the complexity of the relationship between coastal hazards and climate change, a full risk assessment using independent expertise is usually required when considering activities in coastal areas. A simple screening analysis is not generally appropriate for such a task. For further details, see Coastal Hazards and Climate Change on http://www.climatechange.govt.nz/publications/climate/guidance.html.

Qualitative assessment of the impact of climate change

When assessing the possible effects of climate change on a particular council function or service it may be helpful to consider the extent to which council functions and services, and natural resources and hazards managed by councils, depend on climate parameters.

Tables 4 and 5 on the next three pages are designed to help council staff understand and qualitatively determine the role of climate, and hence climate change, for a wide range of council functions and services.

Table 4 looks at specific council functions, assets and activities and how they could be affected by climate change. Table 5 looks at natural resources that are managed by councils and their sensitivity to climate and climate change.

If you already know which council function or service you are dealing with, you may find Table 4 useful. If you are concerned with natural resource or hazard management, and your council's responsibilities in these areas, Table 5 may be more appropriate.

In using these tables, remember that climate change and its effects should be considered relative to other changes because climate change will not occur independently of natural climate variability, and future social and economic changes. This guide does not provide guidance on how to make projections of future socio-economic changes - councils will generally have their own resources to estimate future population change and development projections, and the infrastructure requirements to accommodate these.

Table 4: Local government functions and possible climate change effects

View local government functions and possible climate change effects (large table)

Table 5: Sensitivity of natural resources to present climate and climate change

View sensitivity of natural resources to present climate and climate change (large table)

Deciding on the need for quantitative assessment

Having qualitatively determined that climate change could affect a council function or service, a decision has to be made as to whether the impact warrants a more quantitative analysis.

Quantitative assessment is most likely to be required:

• Whenever infrastructure is upgraded anyway or major developments are undertaken. Some infrastructure and developments have a lifetime of more than 30 years. Is their design consistent with climate predictions?
• Whenever council plans come up naturally for review. If the topic is dependent on climate and the plan regulates long-term actions, it may be affected by climate change.

The following principles are also important in deciding on quantitative assessment:

• Future generations need to be able to respond to risks caused by a changing climate. Avoid locking the community into a situation of increasing risk with limited risk-mitigation options.
• The risk from climate change varies over time. Defer analysis and action on climate change only if its effects are likely to be negligible compared to other pressures, or if a future generation is likely to able to respond equally well or better than the present generation to the specific risk.

Other questions that need to be asked include:

• Is there an existing problem that may be exacerbated by climate change e.g. recurrent inundation?
• Is there a foreseeable problem that may be caused or exacerbated by climate change?
• Is the issue complex e.g. locating a new suburb versus one house?
• Is the location sensitive to climate change e.g. flood plain versus bedrock hillside?
• Is it a permanent long-term change e.g. locating a new suburb versus permitting a campsite?
• Does it involve a lot of infrastructure and are services provided e.g. urban area versus remote rural location.

Quantitative assessment of the impact of climate change

Quantitative assessment of the effects of climate change can be carried out at relatively low cost and effort at the design and planning stages of a major project because it can be integrated into project development. Separate analyses later are likely to be more costly and less effective, as is action to reduce future risk after the project has been completed.

Screening analysis of the significance of climate change

Table 6 on the next page provides guidance on developing scenarios for initial screening and for more detailed study. It provides suggestions, not firm scientific predictions, for scenario analyses. Predictions, especially those for strong winds and heavy rainfall, are likely to be revised as science and modelling develop further.

The table is designed to provide planners and engineers with useful ball-park figures to test the likely significance of climate change on specific council functions and services in an initial screening assessment. This initial risk assessment can usually be undertaken with relatively low investment of resources and may not require independent expertise. It can be carried out as part of a larger planning exercise at minimal cost.

For initial screening purposes, the second column in the table outlines how to obtain region-specific values of climate parameters based largely on figures provided in Part One of this guide. The emphasis is on mid-range climate projections. If they indicate possible material climate change effects, more detailed analysis is recommended. If they do not suggest significant effects, it is advisable to repeat the assessment exercise using the upper range figures. It may also be useful to examine historical data. This could involve a statistical analysis or use of past events (floods, droughts, hot years etc) with additional changes in the underlying average climate as analogues for the future.

More detailed study of the effects of climate change may require a more complex physical or statistical modelling approach, using detailed analyses of current climate statistics in a location and covering the high and low extremes of predicted climate change over the timeframes relevant to the particular function or natural resource being addressed.

Table 6: Values or sources of climate parameters suggested for use in scenario analysis

View values or sources of climate parameters suggested for use in scenario analysis (large table)

Consideration of heavy rainfall in assessing the effects of climate change

Table 7 below reflects the fact that heavy rainfall is a key variable in infrastructure planning and design. The table shows, for screening assessment scenario purposes, recommended percentage adjustments per degree of warming to apply to extreme rainfalls, for various average recurrence intervals (ARIs) and for rainfall durations from less than 10 minutes up to 72 hours. As indicated in Table 5, current extreme rainfall rates for selected locations, durations and ARIs can be obtained from analysis of historical rainfall data sets from particular sites or from the High Intensity Rainfall Design System (HIRDS) CD-Rom (available from NIWA). For temperature, use the projected changes in annual mean temperature from the right hand columns of Tables 2 and 3 of this guide.

At least two screening calculations should be undertaken for low and high temperature change scenarios. A worked example of the application of this information is provided in Appendix 4 of the source report. In carrying out such site-specific analyses, note the uncertainties in return period estimates for the present climate. In many places rainfall records only cover a past period of a few decades, so that design rainfall estimates for 50 or 100-year ARIs contain statistical assumptions and data-based uncertainties.

Table 7: Factors for use in deriving extreme rainfall information for preliminary scenario studies (screening assessments)

This table recommends percentage adjustments to apply to extreme rainfall per degree Celsius of warming for a range of average recurrence intervals (ARIs). The percentage changes are mid-range estimates per degree Celsius and should only be used in a preliminary scenario study. The entries in this table for durations of 24, 48 and 72 hours are based on results from a regional climate model driven by an equilibrium climate model, and will be updated once regional model runs driven by transient climate models are available for New Zealand. The entries for 10-minute duration are based on the theoretical increase in the amount of water held in the atmosphere for a 1°C increase in temperature (8%). Entries for durations between 10 minutes and 24 hours are based on logarithmic (in time) interpolation between the 10-minute and 24 hour rates.

If the use of the range of figures provided above indicates that climate change could significantly affect a council function or service, and this function or service is of sufficiently large scale or importance to warrant attention, a full risk assessment using more complex scenarios may need to be undertaken.

Assessing climate change effects using complex scenarios

Because of the uncertainties involved in climate change, a mixture of quantitative and qualitative information should be used. Assessing the effects of climate change on council functions and services can be approached in any one of three main ways:

• Modelling: computer-generated scenarios of climate change, using either existing models and data, or historical data such as past flood events to determine possible effects in the future.
• Expert opinion: expert advice on plausible scenarios of climate change in a particular region. If, for example, flooding was used in a modelling approach, quantitative analysis could be combined with expert opinion. Lack of data and modelling capability may increase reliance on expert opinion.
• Monitoring: the real effects of climate change will only emerge through ongoing monitoring and, in some cases, may be the only way that effects can be quantified over time.

In selecting which approach to take, judgment will be required as to which is most applicable to the specific problem or issue. Considerable capability - in terms of expertise, data and quantitative models - already exists for assessing physical impacts. For example, there is a strong capability in New Zealand for predicting river flows but there is generally a much lower capability for quantitative assessment of biological and social/human impacts. In areas such as asset management, where investment in infrastructure is required, quantitative modelling is the recommended principal approach. A combination of approaches, especially monitoring, might be used for addressing biodiversity issues.

Uncertainties or assumptions will be inherent in whichever approach is selected. These need to be taken into account, together with the uncertainties in projections of future climate, when assessing climate change effects.

Illustrated below are three different scenarios of varying complexity which have been used in climate change risk assessment.

Scenario case studies

Example 1: Southland water resources

Environment Southland identified three main drivers of change that would affect Southland's fresh water environment in future:

• Environmental: the greatest change has been an increase in the average minimum temperature over the past 40 years. The daily temperature range is decreasing faster than elsewhere in New Zealand.
• Population: the populations of both urban and rural areas have been declining since the late 1970s.
• Economic: agriculture accounts for 82% of the total land area in the region that is not conservation land. Agricultural activities are the largest contributor of nutrients, microbiological and other contaminants to fresh water resources.

Changes in land use can have a major effect on resultant environmental pressures. Over the past decade there has been a rapid expansion of dairy farming and associated industry infrastructure. Tourism is among other economic activities that could increase pressure on fresh water resources.

Thus, if Environment Southland intended studying the possible effects of climate change on Southland's fresh water environment, it would need to consider changes in these key drivers over the next 30 to 100 years. This would require some consideration of alternative scenarios for each driver, as outlined below.

Table 8: Examples of possible alternative scenarios for key drivers affecting Southland fresh water resources

Example 2: Water resource changes in three river catchments

A study was undertaken to quantify the potential change in agricultural water usage and availability due to climate change, and to assess the implication of these changes on the potential pressures on water sources and water allocation issues.

Changes in three river catchments were studied: Rangitata in South Canterbury, Motueka in Nelson and Tukituki in Hawke's Bay.

Environmental (climate and river flow changes) and economic (land use changes) scenarios were developed, though the latter were generated principally by the former.

The main steps in the development of climate and river flow change scenarios were:

• gathering of historical climate and river flow data for 1971-95 for selected sites in each catchment
• generation of two climate change scenarios for 2050, and site changes (monthly) for precipitation, maximum temperature, minimum temperature, dew point temperature and wind
• use of a weather generator to synthesise 30 years of daily climate data for 2050 for key sites
• river flow scenarios.

Land use changes in each of the three catchments were determined by calculation of changes in mean monthly degree-days, combined with local knowledge.

Current economic trends for different crops and farming systems were applied, on the basis that they would hold for 2050. The general pattern presented was for more intensive land use. The scenarios of climate, river flow and land use change were then brought together to quantify possible changes in water demand and supply, using an irrigation scheme simulation model.

Example 3: Stormwater and wastewater effects in North Shore City

A study by North Shore City Council on its wastewater system included examination of the possible effects of climate change on future wet weather overflows.

Existing system performance was translated into expected future performance based on changing rainfall (extreme events) using a statistically established relationship between existing rainfall patterns and existing system performance.

Key aspects of the development of scenarios included:

• the use of 17-year historical rainfall records to determine the existing condition of the receiving environment
• the use of NIWA studies showing likely increases in temperature and rainfall due to global warming
• estimation of storm characteristics in 2050 from the historical records and historical and predicted future rainfall.

The study acknowledged that, although climate change is accepted worldwide as inevitable, its effect on North Shore's wastewater system was based on a number of simplified assumptions with inherent uncertainties associated with modelling the effects of global warming. The results, therefore, should be used to assess trends more than to provide absolute values.

Using a full risk assessment process for climate change effects

A sound risk assessment process is fundamental to ensuring that climate change is appropriately factored into planning and decision-making processes.

The purpose of risk assessment, in the context of climate change, is to identify risks caused or exacerbated by climate change and to evaluate their effects and likelihood. This also allows climate change risks and responses to be prioritised with confidence and compared equitably with other risks, resource availability and cost issues.

Risk assessment has two key steps:

1. A screening level assessment, as explained earlier, to determine whether a formal risk assessment is necessary for the issue being considered.
2. A formal risk assessment process to identify and evaluate risks for any one issue, though it can also be applied to the local authority's operations as a whole. This is explained over the next few pages and is generally warranted if the initial screening analysis has shown that climate change could have a significant effect on an important council function or service.

While the latter process refers only to the risks associated with climate change, these risks are best assessed together with risks from other hazards and climate variability where possible i.e. not in isolation. The process outlined is not the only one that can be used. If a local authority has an existing risk assessment process, climate change can simply be added in.

The long-term nature of climate change means that the lifetime of a development, service or infrastructure must be considered when assessing risk. The risk may not exist now, but may evolve due to climate change.

This risk assessment, therefore, recognises the time evolution of risks by introducing a planning horizon and considering the risk at various steps along the way. For a lifetime of 100 years the risk may be evaluated as it is now and as it will be in 25, 50, 75, and 100 years, giving options for responses over time.

Conclusion

Local authorities are responsible for a range of functions, services and assets that may be affected by climate change. Each community will have its own climate-related vulnerabilities and priorities.

This guide has emphasised the need to assess the potential effects of climate change on council activities and has provided a framework for doing so. A key recommendation is that councils consider climate change effects - and the additional risks and opportunities they may bring - as part of existing planning, risk assessment and operational processes. Generally speaking, councils can also respond to climate change effects via existing processes.

Decisions as to whether a climate change response is necessary should include consideration of legislative frameworks (including hazard management responsibilities, liability and existing use right considerations), community expectations for the present and the future, and the relative costs and risks of delaying action.

A distinguishing feature of climate change-related risks is that the underlying risks themselves change over time. It is important to consider whether future generations will be in a position to adequately address these changing risks if the present generation defers action.

In all cases, it is recommended that councils monitor and record local climate variables in order to better inform risk assessment and associated decision-making in their area.

By responding now to climate change impacts, councils can improve the resilience of their communities to existing natural hazards and, in so doing, enhance the prosperity and sustainability of present and future generations.