Allocation of pollution and carbon emission reduction targets for city clusters: Empirical evidence from China's Yangtze River Delta city cluster based on cost optimization

The rational allocation of pollution and carbon emission reduction targets for city clusters, particularly the Yangtze River Delta (YRD), which has the largest economic scale in China, is critical for fostering regional economic growth, facilitating coordinated emission reductions, and improving environmental quality. This study integrates the principles of fairness, capacity, and efficiency. It utilizes the stochastic impacts by regression on population, affluence, and technology (STIRPAT) model and planning models to develop the lowest-cost allocation scheme for pollution and carbon emission reduction based on the reduction targets for the YRD city cluster. The results indicate the following. (1) The integrated air pollutant emissions in the YRD city cluster exhibit a fluctuating upward trend, with population size having the greatest impact. (2) Regional development within the YRD city cluster is uneven, with coastal cities generally exhibiting higher maturity than inland cities. Shanghai has the highest maturity, while Chizhou exhibits the lowest. (3) The emission reduction targets for the city cluster and the high, medium, and low maturity groups are 2,200,753 tons of equivalent, 1,035,610 tons of equivalent, 572,800 tons of equivalent, and 592,343 tons of equivalent, respectively. Although the use of the maturity indicator causes an allocation of more emission reduction tasks to cities in the high maturity group, most cities in the low maturity group require a larger proportion of emission reductions. The research findings have significant policy importance for establishing a fair and effective emission reduction target allocation mechanism, achieving regional total emission control, and stimulating collaborative emission reduction efforts.