# Effects of changing population or density on urban carbon dioxide emissions

## TL;DR

This paper introduces a comprehensive framework to analyze how population and area, along with their interactions, influence urban CO2 emissions, revealing that population changes have a greater impact than density variations.

## Contribution

It develops a generalized model considering population, area, and their interactions, improving emission predictions and uncovering the coupled effects of urban metrics.

## Key findings

- Population changes have a greater effect on emissions than density changes.
- Larger cities show a higher impact of population or density variations on emissions.
- The model accounts for initial values of population and area in emission variations.

## Abstract

The question of whether urbanization contributes to increasing carbon dioxide emissions has been mainly investigated via scaling relationships with population or population density. However, these approaches overlook the correlations between population and area, and ignore possible interactions between these quantities. Here, we propose a generalized framework that simultaneously considers the effects of population and area along with possible interactions between these urban metrics. Our results significantly improve the description of emissions and reveal the coupled role between population and density on emissions. These models show that variations in emissions associated with proportionate changes in population or density may not only depend on the magnitude of these changes but also on the initial values of these quantities. For US areas, the larger the city, the higher is the impact of changing its population or density on its emissions; but population changes always have a greater effect on emissions than population density.