Effect assessment and policy optimisation of synergy between pollution and carbon reduction in the Yangtze River Delta, based on composite-system co-ordinating-degree model

Context The growth of contemporary industry has led to significant problems with carbon emissions. The Chinese government has set particular emission reduction goals and places a high priority on this issue.Aims Synergy effect of Chinese policies for reducing pollution and carbon emissions are analysed from two subsystems including pollution reduction and carbon reduction, by using the four provinces and cities of the Yangtze River Delta as the research objects.Methods Composite-system co-ordinating-degree model was used to evaluate order degree, internal co-ordinating degree and composite-system co-ordinating degree, with provincial panel data from 2011 to 2020 of four provinces and cities in the Yangtze River Delta being analysed as well.Key results First, the order degree of pollution-reduction and carbon-reduction subsystems in the Yangtze River Delta showed a slow-rising trend; second, the level of internal synergy degree of two subsystems was not readily apparent; and last, but not least, co-ordinating degree of composite system of pollution-reduction and carbon-reduction subsystems were at a low level.Conclusions Overall based on the above research conclusions, we propose several efficiency-enhancing policies, including optimisation of regional target co-ordination, further improvement of regional management-system design, establishment of regional resource-sharing mechanism and technological innovation system.Implications The efficiency-enhancing policies mentioned above contribute to advancing the construction of the national (sic)(sic)(sic)(sic) ['Waste-Free City'] initiative and promoting the realisation of the national (sic)(sic) ['carbon peaking and carbon neutrality'] goals.