Analysis of the latest census data for 2000 and 2010 shows that 88 out of 336 Chinese municipalities suffered combinations of total, urban and hukou population loss. A general ordered logit model examines the ways manufacturing decline, services growth and demographic vitality interact in a specifically Chinese context of population control, contributing empirically and theoretically to studies of city shrinkage. Chinese experience shows that while some cities act as growth engines in emerging economies, others may shrink, and this process may happen before the completion of a rural–urban transition. These findings call for a modification of China’s growth-oriented urban policy.

Continuous urbanisation, rising energy usage, and CO₂ emissions challenge global sustainability. Current understanding is fragmented due to regional research differences and conflicting data sources. We used RS and GIS technologies to create a comprehensive dataset on global urban CO₂ emissions (2000−2020). Besides population and density, we included land area size and physical compactness. Our findings indicate that higher population density may reduce emissions, physical compactness can increase them, and land area size influences emissions more than population size. Thus, strategic planning is essential for emission reduction. We found varied relationships between per capita emissions and population density and between emission intensity and compactness. Different cities face unique challenges based on location and development stage. Developing economies, especially in Africa, face significant challenges as emission scaling shifts from sublinear to superlinear with urbanisation. Large cities should reduce fossil fuel use and adopt eco-friendly technologies, while smaller cities should enhance emission efficiency.