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Minimizing Urban Carbon Emissions and Heat Island Intensity: A theoretical study
Fabian Reitemeyer1,2, Fabiano L Ribeiro3, Jan Schwarz4
1District Office Friedrichshain-Kreuzberg, Organizational Unit Climate and International, Berlin, Germany.
Plos One
|September 3, 2025
Summary
Optimizing city size is complex; while higher density reduces carbon emissions, it intensifies the urban heat island (UHI) effect. For German cities, a simultaneous optimum for both is not feasible, suggesting the population-area scaling is the true optimum.
Area of Science:
- Urban planning and environmental science
- Socio-economic geography
- Sustainable urban development
Background:
- Cities present a trade-off between agglomeration benefits and environmental impacts.
- Urban density influences both carbon emissions and the urban heat island (UHI) effect.
- A balanced approach is needed to mitigate these competing urban challenges.
Purpose of the Study:
- To investigate the relationship between city population, spatial extent, carbon emissions, and UHI intensity.
- To derive a theoretical optimal city size that minimizes both carbon emissions and UHI intensity.
- To validate the theoretical model using German city data and existing UHI literature.
Main Methods:
- Defining a combined objective function for carbon emissions and UHI intensity.
- Establishing a constraint based on the scaling relation between city area and population.
- Deriving a theoretical expression for optimal city size.
- Analyzing carbon emission data from German cities.
- Incorporating UHI intensity parameters from scientific literature.
Main Results:
- For German cities, simultaneously minimizing carbon emissions and UHI intensity through optimal city sizing is not physically achievable.
- The existence of an optimal city size depends critically on UHI intensity parameters and the population-area scaling exponent.
- The study suggests that the observed scaling relation between population and area in cities may represent an inherent optimum.
Conclusions:
- Current urban scaling relationships may reflect a natural optimum rather than a target for optimization.
- Policy and planning should consider the inherent trade-offs and scaling laws governing urban form and environmental impact.
- Further research could explore alternative urban configurations or technological solutions to mitigate environmental challenges.
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