Urban carbon flow and structure analysis in a multi-scales economy

With the increasing threat of global climate change, carbon emissions reductions in cities have aroused the concern of the world. Carbon flow is one of the profiles that is closely connected to the urban metabolic system. Here, a global environmentally extended multi-scale input-output model was employed to accurately trace the carbon flow in a multi-scales economic system from production and consumption perspectives. Beijing was selected as the case, and the results were as follows: Beijing is typically a net importer of carbon flow (net consumer), which is consistent with Beijing's profile as a consumer metropolis. Further, all seven domestic regions in China were net producers corresponding to Beijing, supporting nearly 96.56% of the net carbon inflows driven by Beijing's final demand. Beijing mainly imports carbon flows from domestic regions and developing areas around the world, while exporting little to developed countries. Aside from the Mining (S2), Nonmetallic (S9), and Transport (S17) sectors, all other industrial sectors were net inflows of carbon for Beijing in 2010. In addition, Beijing is located at the bottom of the global production supply chain, transferring the embodied carbon flow to the origin by domestic and international imports. These results indicate that regional coordination and regional trade structure adjustment should be the main measures to tackle global climate change in the future.