The efficient, the intensive, and the productive: Insights from urban Kaya scaling

Abstract

Urban areas play an unprecedented role in potentially mitigating climate change and supporting sustainable development. In light of the rapid urbanisation in many parts on the globe, it is crucial to understand the relationship between settlement size and CO 2 emission efficiency of cities. Recent literature on urban scaling properties of emissions as a function of population size have led to contradictory results and more importantly, lacked an in-depth investigation of the essential factors and causes explaining such scaling properties. Therefore, in analogy to the well-established Kaya Identity, we develop a relation combining the involved exponents. We demonstrate that application of this Urban Kaya Relation will enable a comprehensive understanding about the intrinsic factors determining emission efficiencies in large cities by applying it to a global dataset of 61 cities. Contrary to traditional urban scaling studies which use Ordinary Least Squares (OLS) regression, we show that the Reduced Major Axis (RMA) is necessary when complex relations among scaling exponents are to be investigated. RMA is given by the geometric mean of the two OLS slopes obtained by interchanging the dependent and independent variable. We discuss the potential of the Urban Kaya Relation in main-streaming local actions for climate change mitigation.

Effects of changing population or density on urban carbon dioxide emissions

“…We note that the models of Eqs. (5) and (20) provide significantly lower values when compared with all other models; however, no significant difference is observed between these two models. It is worth noting that these coefficients include a penalty term that depends on the number of parameters, allowing a fair comparison among models with different number of parameters.…”

“…, the full translog model of Eq (20). does not improve the goodness of the fit when compared with Eq.…”

“…This fact assigns cities a central role in pursuing solutions and mitigation strategies for the global climate change problem. Because of that, researchers from several disciplines have investigated the effects of urbanization on CO 2 emissions [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] . The question of whether urbanization promotes or mitigates climate change is ubiquitous among these works, and the approaches to probe such issues differ, but can be roughly organized into two groups.…”

Space-based quantification of per capita CO2 emissions from cities

“…Studies focusing on urban agglomeration and carbon emissions have increased in number within the past few decades. Some have related total carbon emissions to total population (Fragkias et al 2013, Oliveira et al 2014, Gudipudi et al 2019 while others used per capita emissions versus population density (Gately et al 2015, Gudipudi et al 2016. The conversion between these two scaling relations requires an assumption of urban area when converting population density to total population or E pc to total emissions (SI appendix, text B).…”

“…To address the impact on emissions from competing factors, Fragkias et al (2013) and Gately et al (2015) examined their emission-population relationship with additional factors such as per capita personal income, job density, and population growth rate. Recent efforts have been made towards overcoming the possible confounding effects from urban area, GDP, and energy consumption, using sophisticated frameworks further inspired by the economic theory of production or the Kaya Identity (Gudipudi et al 2019, Ribeiro et al 2019.…”