EO4NBS

Summary

Nature-Based Solutions (NBS) are increasingly being implemented in urban areas as part of broader climate adaptation strategies, but challenges remain to determine their cooling effects, partly due to lack of reliable baseline measurements and long-term monitoring.

EO4NBS will use Earth Observation data, including long-term records of Essential Climate Variables (ECVs) to “fingerprint” the effects of NBS, determine which EO products can be used to inform those effects, and make longitudinal studies in use-case cities to determine local climatic effects before and after implementation of NBS. This will be followed by a pan-European study and roadmap for upscaling.

EO4NBS will directly contribute to the Global Goal on Adaptation indicators by working on remote-sensing solutions that point towards consolidated guidance on what best practices can be adopted in NBS planning and design.

Project background

Rising temperatures and more frequent extreme heat events are emerging as one of the most urgent climate-related risks to human health, particularly in rapidly urbanising areas. Episodes of extreme heat, especially in cities, are now recognised as a major driver of excess mortality and morbidity in Europe, disproportionately affecting vulnerable groups and increasingly stressing public health systems (EUCRA, 2024).

While originally promoted primarily for managing hydrological risks (Sørup & Arnbjerg-Nielsen, 2021), Nature Based Solutions (NBS) are now expected to deliver a range of co-benefits, including urban cooling, enhanced ecosystem services, and improved wellbeing (Viti et al., 2023; 2024). Among these, heat mitigation and associated health benefits have a strong theoretical foundation and are widely cited as key arguments for investing in NBS (Kabisch et al., 2017; Kumar et al., 2024).

However, despite growing policy interest, empirical quantitative evidence of the realised cooling effects of implemented NBS remains limited. This is partly due to the methodological challenges of measuring localised temperature reductions using traditional ground-based instrumentation, as intra-urban weather station networks are scarce and, when available, often rely on short-lived research projects with limited temporal coverage. At the same time, many cities are implementing NBS at an unprecedented pace (CONCITO, 2024) with limited long-term monitoring systems or management plans, which limits the opportunity to learn from previously implemented projects and inform future decision-making.

Earth Observation (EO) has the potential to close this critical data gap. Satellite-derived vegetation indices can monitor changes in urban greening, tree cover and green space over time, while remote sensing products describing land surface temperature can support assessments of air temperature, relative humidity and population heat exposure in dense urban areas affected by the Urban Heat Island (UHI) effect.

Important knowledge gaps nevertheless remain in using EO to assess adaptation to urban heat. As Connors et al. (2025) highlight, accurate and context-specific baselines are essential for attributing post-intervention changes and require the integration of EO with in-situ, socio-economic and modelling data. Only with pre-intervention data built on sufficiently complete input data (spatially and temporally) it is possible to attribute subsequent temperature changes to the intervention rather than to interannual climate variability or other confounding factors (including behavioural changes).

Therefore, this project will utilise long time series of relevant Essential Climate Variables (ECVs) and other long term EO datasets to establish baseline local climate conditions before NBS implementation and compare them with recent local climate conditions, enabling a more robust assessment of the realised effects of NBS.

Project aims and objectives

The EO4NBS project will:

• Fingerprint the expected effects of NBS, and determine which ESA CCI ECVs (or other EO products) can potentially be used to inform those effects. EO4NBS will make longitudinal studies of relevant ECVs and EO products in use-case cities to determine local climatic effects before and after implementation of NBS at the:
  • Resolution level of the data product; i.e. what can be measured at the grid cell where the NBS is located vs. in a grid cell where no change has taken place?
  • Neighbourhood level; how much an effect can be measured as one moves away from the NBS, and what is the expected area of effect and the characteristic effect within this area?
  • City level; can the combined effects of all implemented NBS be measured at the city scale to a degree where it can help inform politicians on expected effects of implementing NBS as part of climate change adaptation strategies?
• Use the case result to make fingerprints of commonly seen NBS strategies across relevant ECVs and EO products at the local to city scale
• Test the fingerprints in a pan-European setting combining relevant databases on implemented NBS to fingerprints calculated at the city scale from actual measurement.
• Use the fingerprint test to lay out a roadmap for upscaling to the continental and possible global scale.

The project will implement three case studies focusing on urban implementation of NBS:

1. A Danish case study will use local high-resolution data products for validation. It will include a component where the DestinE’s Climate Change Adaptation Digital Twin will be used to evaluate effects in a changed climate.
2. A Swedish case study will likewise utilize existing high-resolution heat models for validation.
3. A pan-European study will focus on city-level fingerprinting and validate against global-scale alternatives where possible.

All case studies will carry out formal uncertainty propagation and quantification work, with the last focusing on uncertainty propagation in relation to upscaling.

The project adopts the IPCC risk assessment framework, which defines climate risk as the result of interactions between hazard, exposure, and vulnerability, each influenced by both climatic and non-climatic drivers. This structured approach provides a consistent basis for assessing the impacts of urban heat, understanding the differentiated risks across city neighbourhoods, and identifying where adaptation interventions, including NBS, can effectively reduce heat-related health impacts.

Project plans

Towards the goals described above, the project work is structured into five Work Packages (WP):

• WP1000: Review of the state-of-the-art and Scientific Requirements
  This WP will perform a state-of-the-art review and initial mapping of relevant ESA CCI ECV datasets and translate this into a coherent set of scientific and technical requirements for the project. The insights from the literature review and the engagement with CCI teams provide a basis for identifying which ECV datasets, auxiliary EO products, and derived indicators are most suitable for supporting a longitudinal, pre-/post-NBS assessment across different spatial scales.

• WP2000: Development of the methodology, data creation and tool preparation
  This WP will focus on establishing an initial version of the data pipeline required to support both the NBS assessment and the application of the temperature downscaling model. Furthermore, this WP will employ the machine-learning–based temperature downscaling models derived from methodologies developed in projects such as CLIM4cities, DeltaTwin and CLIM4health, to address historical assessment of changes and onward looking climate scenarios.

• WP3000: Scientific Analysis and Case Studies

1. Danish case study: focused on the greater Copenhagen metropolitan area, as well as the two to three largest cities outside this area. These exhibit clear urban heating effects and have been extensively studied in other contexts, providing ample opportunity to validate the findings against previous results.
2. Swedish case study: focused on the cities of Malmö and Norrköping, both of which have long-standing climate adaptation strategies and a diverse portfolio of implemented NBS. Together, the two cities represent distinct urban sizes and climate conditions, enabling a broader assessment of how NBS performance varies across different Northern European contexts.
3. Pan-European case study: the goal is to develop an EO-based indicator that captures the threshold or scale of urban greening required to produce a measurable difference in urban thermal signals in cities with population greater than 50,000 in Europe where NBS has been implemented, and to validate them with the vegetation index indicators.

• WP4000: Roadmap Development
  Based on the case studies, this WP will set forward a path for upscaling. The Danish and Swedish case studies will inform what can realistically be measured at what scales, while the pan-European study provides insight into the operationalisation challenges associated with large-scale upscaling. Uncertainty propagation experiences will be used to discuss challenges regarding data input and uncertainties.

• WP5000: Communication and Outreach
  This WP covers the administrative and financial management to ensure timely delivery of project results and smooth collaboration. It oversees communication and outreach activities, including local stakeholder outreach, website content, attendance to workshops and conferences, and scientific publications.