On the impact of Urbanisation on CO2 Emissions
We use a globally consistent, time-resolved data set of CO2 emission proxies to quantify urban CO2 emissions in 91 cities. We decompose emissiontrends into contributions from changes in urban extent, population density and per capita emissions. We find that urban CO2 emissions areincreasing everywhere but that the dominant contributors differ according to development level. A cluster analysis of factors shows that developingcountries were dominated by cities with rapid area and per capita CO2 emissions increases. Cities in the developed world, by contrast, show slow area and per capita CO2 emissions growth. China is an important intermediate case with rapid urban area growth combined with slower per capita CO2 emissions growth. For many developed countries, urban per capita emissions are often lower than their national average suggesting that urbanisation may reduce overall emissions. However trends in per capita urban emissions are higher than their national equivalent almost everywhere suggesting that urbanisation will become a more serious problem in future. An important exception is China whose per capita urban emissions are growing more slowly than the national value. We also see anegative correlation between trends in population density and per capita CO2 emissions, highlighting a strong role for densification as a tool toreduce CO2 emissions.