China　is　an　important　fossil　fuel　CO2　(CO2ff)　emitter　and　the　international　community　is　thus　concerned　with　quantifying　reductions　in　Chinese　carbon　emissions　in　the　recent　past.　Compared　to　traditional　statistical　method,　radiocarbon　(14C)　offers　a　different　approach　to　quantify　atmospheric　CO2　derived　from　fossil　fuel　emissions.　Here,　we　carry　out　a　multi-year　(2011–2016)　CO2ff　tracing　by　14C　in　Xi＇an,　and　a　three-year　(2014–2016)　CO2ff　tracing　in　15　Chinese　cities.　The　Xi＇an　results　show　that　average　CO2ff　concentrations　fell　35.9　±　6.6%　from　2014–　2016,　compared　to　2011–2013,　and　the　timing　of　this　decrease　coincides　with　the　implementation　of　nationwide　carbon　reduction　measures　in　China,　known　as　the　Action　Plan　on　Prevention　and　Control　of　Air　Pollution.　A　WRF-Chem　forward　modeling　simulation　reveals　that　the　CO2ff　in　Xi＇an　is　mainly　derived　from　local　sources,　and　a　source　apportionment　combined　stable-carbon　isotope　showed　that　the　CO2ff　in　this　city　is　dominated　by　coal　combustion　(72.6　±　10.4%).　Strong　CO2ff　differences　are　found　between　January　and　July　in　most　Chinese　cities.　High　CO2ff　concentrations　often　correspond　to　severe　haze　episodes　and　there　are　generally　positive　correlations　between　CO2ff　and　fine　particulate　(PM2.5)　concentrations.　Our　study　provides　scientific　data　to　understand　the　effects　of　CO2ff　reduction　strategies　in　China　that　can　be　applied　to　other　countries　as　well.　©　2018　Elsevier　B.V.