Sydney Science Park: Summer Air and Soil Temperatures 2023-24

Transforming open, vegetated space to new settlements results in warmer microclimates. This is because the introduction of materials with a low solar reflectivity and high capacity to store and re-emit solar energy leads to warmer air and surface temperatures. Waste heat from anthropogenic activities further adds to warming. In a climate change era, it is necessary to plan and develop settlements that will keep cool in increasingly hotter summers. Yet, the apparent lack of detailed information about microclimate conditions of an area prior to development (i.e., ante constructio) limits our capacity to quantify the amount of warming caused by development and subsequent changes to its design to reduce these warming effects. It is the lack of ‘before-after’ microclimate data that prevents evidence-based planning and design of cooler settlements. Here we establish a baseline of summer air and soil temperatures across the Sydney Science Park before the site is developed. This project demonstrates leadership towards data-based urban planning and design that informs the construction of cooler settlements. Microclimatic variability across the 420-hectare site was documented from 1 December 2023 to 29 February 2024. More than 560,000 measurements – 524,160 of air temperature and 37,308 of soil temperature – were collected. Key findings: - The average variation of air temperatures among 29 measurement locations spanning the entire site was 1.2°C (22.9-24.1°C) - Maximum daytime air temperature differences across the site were as high as 8°C. - The northwest of the site was cooler during the day than the southeast. - Being close to water reduced day- and nighttime air temperatures. - The Cottage site had the warmest microclimate. - The area in the southeast that will be developed first had the highest air temperatures during an extreme heat event. - Like air temperature, soil temperature was lower in the western section of the site compared to the east, despite having more water bodies in the east. Transforming the site from pastures to thriving urban spaces will require extensive landscaping and extensive planting of trees. Optimal air and soil temperature for plants growing in temperate climates are between 20°C and 30°C. Mean soil temperatures at the Sydney Science Park ranged from 24°C to 26°C, however daily maximum temperature of topsoil regularly exceed 30°C. Keeping topsoils cool will assist in maintaining tree health and thus speed up canopy cover across the site. This project has established the microclimate baseline of the Sydney Science Park prior to development activities. Identical data collections should be repeated on a regular basis (i.e., every 3 years) to develop a refined understanding of the temperature dynamics introduced by urban development. The site offers a unique opportunity to quantify the thermal impacts of land use change in Western Sydney and assess the efficacy of a wide range of urban heat mitigation strategies using blue-green infrastructure, climate-responsive design and cool materials.