Are larger or denser cities more emission efficient? Exploring the nexus between urban household carbon emission, population size and density

Considering the high impact of urbanization on climate change , it is pertinent to explore the nexus between household carbon emissions (HCEs), urban population size and population density in Indian cities so as to test whether larger or denser cities are carbon emission efficient. In this study, the statistical significance and variations of mean per capita HCEs are evaluated across six classes of Indian cities classified on the basis of population size and, five classes based on population density by conducting analysis of variance followed by post-hoc test. The results clearly demonstrate that larger or denser cities are not emission efficient. In addition to that, by revisiting scaling laws, it is analytically deducted that for a city to qualify for exhibiting simultaneous emission efficiency in relation to population size and density, population size exponent (α) must lie between 0 and 0.5 and the value of density exponent (β) must be greater than α and lower than unity. By quantifying, comparing and tracking carbon emission efficiencies of cities based on population size and density parameters, the findings of this study potentially provide new insights to policy makers towards approaching the highly ambitious decarbonization goals stated in India's Panchamrit commitment, 2070. • Emission efficiency index covering all Indian cities across six classes. • Larger or denser cities in India are not emission efficient. • Population size exponent (α) must lie between 0 and 0.5 for emission efficiency. • Density exponent (β) must lie between (α) and unity for emission efficient cities.