Providing climate change advice for New Zealand

National-scale climate change projections

Following the release of the Fifth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC), in 2016 NIWA developed national-scale climate change projections for the Ministry for the Environment. These projections were updated in 2018 with the addition of results from a report on very extreme rainfall (the HIRDS report; Carey-Smith et al., 2018).

You can download these national-scale projections from the Ministry for the Environment’s website.

The following report distils and interprets information relevant to Aotearoa New Zealand from the Working Group 1 contribution to the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report titled ‘The Physical Science Basis’, published in August 2021:

Aotearoa New Zealand climate change projections guidance: Interpreting the latest IPCC WG1 report findings

Regional variation in climate change impacts across New Zealand

The impacts of climate change will vary across different parts of New Zealand. For example, the west coast of the South Island is projected to experience more rainfall than at present, while the east of the South Island is projected to experience reductions in rainfall. Similar variations are expected for other aspects of climate – such as average temperatures, hot days, frost days, humidity and wind.For this reason, regional-scale climate change projections can be more useful for New Zealand's local and regional councils. Regional-scale projections can help with assessing local risks from a changing climate and preparing communities for future impacts.

Regional-scale climate change projections

NIWA has provided regional-scale high resolution (5 km x 5 km) maps and detailed reports to a number of New Zealand local government bodies (regional, district, and city councils).

These maps show projections for a large range of climate variables at 2040 and 2090 and for two different climate change scenarios (based on the trajectory of greenhouse gas concentrations in the future).

Along with descriptions of the projected future changes to different climate variables, these reports have been tailored to each region following discussions about sectors of concern. These may include impacts of climate change on aspects including biodiversity, biosecurity, river flows, aquaculture, agriculture, storm surges and groundwater, among others. Climate variables that were mapped include temperature, precipitation, wind, humidity, soil moisture, and solar radiation. Indices and threshold information has also been produced (e.g. changes to the numbers of ‘hot days’ or days above 25 degrees per year). GIS layers of the climate projections have also been provided so that the councils may use them in their planning and decision making processes.

Find out more

You can read more about climate change scenarios under the IPCC’s Fifth Assessment Report and NIWA’s work in developing national-scale climate change projections.

Links to NIWA reports for local government (listed alphabetically)

Auckland Council

Bay of Plenty Regional Council

Full technical report (2019)

Environment Canterbury

Full technical report (2020)

Environment Southland, Gore District Council, Invercargill City Council, and Southland District Council

Full technical report (2018)

Greater Wellington Regional Council

Gisborne District Council and Hawke's Bay Regional Council

Full technical report (2020)

Horizons Regional Council

Tasman District Council

Waimakariri District Council

Forecasting impacts from extreme weather

Published:

16 November 2023

This research project aims to establish connections between weather and river flow forecasting, inundation prediction, and the associated risks to people and assets, using the RiskScape platform.

Its objective is to better understand and forecast potential impacts from extreme weather events and provide richer information to support effective decision making for Aotearoa New Zealand.

The initial focus will be on flooding as a hazard and researchers will engage with emergency managers and relevant staff in regional and local councils.

Workstream one: Weather forecasting

Improve representation of complex terrain in NIWA’s weather models to better capture the impact of topography on rainfall.
Verify the skill and value of new AI (artificial intelligence)-driven Neural Weather Models (NWMs) over New Zealand. While data-driven weather models have made significant advancements globally, their applicability and operational challenges in a New Zealand context remain unverified. The project will develop a 20-year ensemble hindcast of NWMs, followed by validation to build confidence in the modelling system.
Semi automate process of running a sub-km weather model ahead of extreme events. NIWA has existing capability to run sub-km domains. We will develop automatic systems to identify potential extreme weather in our deterministic and ensemble output and (semi-) automatically run the appropriate sub-km domain.

Workstream two: Hydrology and inundation forecasting

Design and implement an operational ensemble river forecast suite based on a dynamical weather ensemble (NZEns).
Improve river flood forecasts by creating a post-processing river forecast method that uses statistical techniques and machine learning. A hindcast of ensemble river forecasts for the previous years will be generated to produce training and testing datasets.
Enhance a machine-learning approach to interpolate a library of look-up scenario flood depth and extent maps for rapid inundation ensemble forecasts. This will involve designing and implementing an ensemble inundation forecasting suite to produce ensemble inundation flood depth and extent maps.

Workstream three: Hazard and risk forecasting

Design flood impact models to estimate impacts to people and property. For example, physical damage, threats to human safety, disruption.
Create real time property exposure workflow, connecting LINZ exposure information to flood impact models.
Implement a pilot flood impact forecast. The case study will focus on Westport and use ensemble maps.

Page last updated:

7 December 2023

NIWA

Providing climate change advice for New Zealand

National-scale climate change projections

Regional variation in climate change impacts across New Zealand

Regional-scale climate change projections

Find out more