The evolution of carbon footprint in the yangtze river delta city cluster during economic transition 2012-2015

•The top 10 megacities account for more than 60% of the carbon footprint in the Yangtze River Delta city cluster.•Although the whole carbon intensity in YRD declined on the production side, it increased carbon footprint due to an increase in the carbon intensity of part sectors.•The production structure change has promoted emission reduction in the Yangtze River Delta city cluster but promoted emission increases in service-based cities and light industry cities.•Industrial transfer from the Yangtze River Delta city cluster highlights the challenge of carbon leakage.•The economic recession raises the carbon intensity of value-added due to declined industrial profitability.