Fig. 4: Framework for tracking urban physical and virtual carbon metabolism.

To capture the broader carbon impact of an urban economy, we combine physical carbon account and fossil fuel-derived virtual carbon account within a consistent framework of carbon metabolism. First, we track the physical carbon appropriated by a city as goods or raw materials imported from outside (IM), local supply from urban ecosystems (LS), or recycling of materials (RE), and how this carbon is distributed within the urban economy and become part of household storage (HS), changes in stock industrial sectors (SC), gaseous emissions (GE), solid waste (SW), or physical exports as goods (EX). Second, we model the virtual carbon emissions manipulated by a city through its import of products and further allocate them to local (household and government) consumption (HG), capital formation (CF), and exports as final demand (EP).