The Comparision among Four Carbon Footprint Estimation Boundaries of the Sectors Using Chongqing as a Case

International negotiations of reducing CO2 emissions address the question of how to meet commitments with more explicit engagment with subnational action and how to account annual CO2 emissions of each sector of one city. This study is to establish the CO2 inventories focused on four tiers of CO2 emissions form each sector, e.g. agriculture, industry, transportation and tertiary industry. Carbon footprint is chosen to evaluate 28 sectors of Chongqing, from four tiers, including direct emissions, emissions from purchased energy, the total supply chain, supply chain plus industrial process. Results showed that the first two tiers, only cover a small fraction of the total supply chain, especially for industrial sectors. We suggested that desion makers must acquire that tier 3 is intended to aid effective management strategies and climate change policies.