The world’s population is now over 50 % urban, and cities account for the majority of greenhouse gas (GHG) emissions. Many cities are developing strategies to reduce their emissions. Here we show how and why emissions differ between cities. By including upstream emissions in our analysis, we show that GHG emissions attributable to cities exceed those reported in current city inventories. Our study of 10 global cities shows how a balance of geophysical factors (climate, access to resources and gateway status) and technical factors (power generation, urban design and waste processing) determine the GHGs attributable to cities. Within the overall trends, however, there are differences between cities with more or less public transit, as well as in heating (building characteristics). Our findings should help foster inter-city learning on reducing GHG emissions.
Christopher Kennedy1*, Julia Steinberger2, Barrie Gasson3, Yvonne Hansen4, Timothy Hillman5 , Miroslav Havránek6, Diane Pataki7, Aumnad Phdungsilp8, Anuradha Ramaswami9, Gara Villalba Mendez10
1. Dept. of Civil Engineering, University of Toronto, Canada (35 St. George Street, Toronto, M5S 1A4; [email protected]; +1 416 978 5978).
2. IFF/Social Ecology, Austria (Schottenfeldgasse 29, A-1070, Wien; [email protected]; ++43-1-5224000-411).
3. School of Architecture and Planning, University of Cape Town, South Africa (7701 Rondebosch, Cape Town; [email protected]; +27 21 650-2366).
4. African Centre for Cities, University of Cape Town, South Africa (7701 Rondebosch, Cape Town; [email protected]; +27 21 650 5903)
5. Dept. of Civil Engineering, University of Colorado Denver, USA (Campus Box 113, P.O. Box 173364, Denver, CO 80217-3364; [email protected]; 303 556-4734 ).
6. Charles University Environment Center, Czech Republic (U Krize8, 15000 Prague; [email protected] ; +420251080351)
7. Dept. of Earth System Science and Dept. of Ecology & Evol. Biology, University of California, Irvine, USA (Irvine, CA 92697-3100; [email protected]; +1 949-824-9411).
8. Dept. of Energy Management, Dhurakij Pundit University, Thailand (110/1-4 Prachachuen Rd., Laksi, Bangkok 10210, [email protected]; +662 954 7300 Ext. 587).
9. Dept. of Civil Engineering, University of Colorado Denver, USA (Campus Box 113, P.O. Box 173364, Denver, CO 80217-3364; [email protected]; 303 556-4734 ).
10. Institut de Ciència i Tecnologia Ambientals, Autonomous University of Barcelona (Edifici Cn 08193 Bellaterra; [email protected]; +93.581.24.88).