Executive Summary

Urban heat risk is a growing concern for Auckland. Rising temperatures, urban expansion, and socioeconomic vulnerabilities are expected to increase heat-related impacts for its citizens. This includes not only heat-related illnesses and deaths but also other significant effects such as reduced productivity, strain on infrastructure and critical services, and indirect issues like ecological and environmental deterioration, similar to what has been observed in other cities globally.

Auckland Council commissioned Arup to produce a heat dataset, which would provide insight into how temperatures vary across Auckland, including the Auckland urban area and the wider Auckland region encompassing rural areas; referred to as the Area of Interest (AOI) in this assessment. The intention of the dataset is to support communication on heat related hazards and to inform decision making for Auckland Council. Furthermore, there is potential for this heat dataset to find synergies in heat and carbon mitigation solutions, for example implementing nature-based solutions in hotspots, etc. The data can also inform climate change risk assessment for Auckland.

Method

Arup have used a novel approach to deliver this dataset, involving the coupling of two state-of-the-art climate modelling tools: WRF (weather research and forecasting) and UHeat.
- WRF enabled the regional variation in climate across Auckland to be incorporated, particularly wind, which can significantly affect the urban heat island effect. Due to the large geographical area and Auckland's specific geographical and topographical characteristics, representing large scale climate was important in producing an accurate dataset.

- UHeat predicts the urban heat intensity across cities at a high resolution, accounting for the parameters that influence the urban environment such as land surface cover, building massing, heat emissions and albedo.

Key Findings

This resulting dataset consists of temperature predictions near street level (2m above ground) for the period from November 2021 to March 2022 (Auckland’s hottest summer on record to date) at a high resolution of 300 x 300m for the AOI. The data has been aggregated in this report to show how daily minimum, average and maximum temperatures vary across the AOI providing insights into the climate variations across the region as well as the magnitude of the urban heat island (UHI) effect in the city centre.

Key insights from the UHeat modelling:
- Auckland’s city centre experiences an UHI effect. A nighttime UHI effect is predicted, with temperatures up to 3°C warmer than rural areas.
- Daytime cooling of the city centre. The data shows this area is sometimes cooler than some surrounding regions during the day, likely due to local wind patterns.
- Temperature variation in the Auckland city centre area. Up to a 3°C variation was predicted within different locations in the city during a peak temperature day.

Conclusions

The UHI effect, as demonstrated by the dataset, combined with increasing urbanisation and the impacts of climate change indicate the need for heat planning and adaptation for Auckland to ensure present and future resilience.

This project has provided a valuable first step for both short and long-term planning in response to the potential impacts of heat and extreme temperatures for Auckland. The dataset can be utilised in a number of ways:

- Publications and data sharing: Make the data publicly available for stakeholders like public bodies, private sector, and the community. An interactive web portal can enhance accessibility.

- Data layering to understand risk: Combine the heat dataset with other data to create detailed heat risk maps, aiding decision-making.
- Community engagement: Use the data to inform and support communication on heat-related hazards and resilience, involving the community in mitigation strategies.
- Gaining insights: Further analyse the data to understand hot and cool spots and the potential for heat mitigation.
- Planning and development: Use the dataset to inform adaptation programmes, targeting areas most affected by heat to improve climate resilience .

There are also several avenues that can be explored to build on this work. Key follow-up steps include:
- Incorporating updates to understanding change: Use the latest geospatial data to refine the analysis and evaluate changes with time.
- Producing heat stress maps: Create detailed maps highlighting areas most affected by heat stress, accounting for other contributing environmental factors.
- Scenario testing: Evaluate the effectiveness of various heat mitigation strategies.
- Climate change projections: Integrate climate change projections to inform adaptation planning.

Beyond this project, Auckland can review adaptation measures and heat mitigation solutions other cities have successfully implemented to establish their own programmes. The challenge is to identify the most effective strategies for Auckland, focusing on heat mitigation and holistic benefits. The heat dataset produced in this project is crucial for prioritising efforts, communicating with stakeholders, and driving action on heat.

This report provides a detailed overview of the methodology, a summary of the results from the UHeat model, and further discussion about use of the dataset and potential next steps.

See also: Summary

Auckland Council, October 2024