Structural evolution of China's intersectoral embodied carbon emission flow network.

Mount of embodied carbon emissions flow along industrial chains and form a complex network. In order to reveal the structure and evolution characteristics of embodied carbon emission flow network among China's industrial sectors, this study applies a complex network theory to construct six embodied carbon emission flow networks with 30 sectors on the basis of China's input-output tables from 2002 to 2015. Through the analysis of complex network technology indicators, the overall structural characteristics of the network, the key sectors, and the key flow paths are analyzed. Main results show that six embodied carbon emission flow networks all have the small-world characteristics; there is an industrial cluster phenomenon in the network. During the study period, construction, manufacturing, and service-related industry community are the absorption sites for embodied carbon emissions. Coal- and petroleum-related industry communities are the divergent sites for embodied carbon emissions; moreover, electric and heat power and fuel processing are the important "suppliers" of embodied carbon emissions; construction and other service are the important "consumers" of embodied carbon emissions. Non-metallic products are the important "transmitters" of embodied carbon emissions. Metal smelting and chemical industry are at the core of the network because of their high weighted degree and betweenness centrality. The central effect of key sectors continues to increase over time; furthermore, the distribution of embodied carbon emission flows in the six networks all have long-tail characteristics, and this characteristic became more prominent over time. There are key edge-weights in the networks. About 11 to 15% of the edges carry 80% of the embodied carbon emissions. Further based on edge-weight analysis, this study identifies the key paths of embodied carbon emission flow in the six networks, and most key paths pass through construction. Thus, such key sectors and key flow paths should receive more attention when making carbon emission reduction policies.