A fine spatial resolution modeling of urban carbon emissions: a case study of Shanghai, China

International audienceQuantification of fossil fuel carbon dioxide emissions (CEs) at fine space and time resolution is a critical need in climate change research and carbon cycle. Quantifying changes in spatiotemporal patterns of urban CEs is important to understand carbon cycle and development carbon reduction strategies. The existing spatial data of CEs have low resolution and cannot distinguish the distribution characteristics of CEs of different emission sectors. This study quantified CEs from 15 types of energy sources, including residential, tertiary, and industrial sectors in Shanghai. Additionally, we mapped the CEs for the three sectors using point of interest data and web crawler technology, which is different from traditional methods. At a resolution of 30 m, the improved CEs data has a higher spatial resolution than existing studies. The spatial distribution of CEs based on this study has higher spatial resolution and more details than that based on traditional methods, and can distinguish the spatial distribution characteristics of different sectors. The results indicated that there was a consistent increase in CEs during 2000-2015, with a low rate of increase during 2009-2015. The intensity of CEs increased significantly in the outskirts of the city, mainly due to industrial transfer. Moreover, intensity of CEs reduced in city center. Technological progress has promoted the improvement of energy efficiency, and there has been a decoupling between the economic development and CEs in the city was observed during in 2000-2015. Greenhouse gas emissions, such as carbon dioxide, contribute to global warming 1 , which is a threat for humans 2,3. Studies have shown that urban areas account for 2% of the total land area, but produce 80% of the greenhouse gas emissions 4,5. In 2014, the urban population exceeded 65% of the global population 6. Cities are the main areas of human activity and greenhouse gas emissions 7. To cope with global climate change and protect the environment, greenhouse gas emissions have drawn increasing attention 8. However, urban expansion and population growth have driven increasingly intensified carbon dioxide emissions (CEs) in cities, particularly in China 9. In recent decades, China has experienced rapid economic growth, environmental damage, and massive energy consumption. In 2014, the CEs of China were 10.29 billion tons, 4.21 times that in 1990, far higher than those of the United States (5.25 billion tons) and other developed countries (https:// data. world bank. org). To date, extensive validation of CEs and their environmental effects have been conducted 10,11 , and measuring CEs from energy consumption has received increasing attention 12-14. For example, Lu 15 quantified and analyzed the impact of CEs from fossil fuel consumption at the national level. Wang 16 analyzed the driving factors of CEs in China. Numerous studies have been conducted on carbon dioxide accounting. Methods of measuring CEs from various processes are developed. Three methods are widely used for carbon accounting: bottom-up, topdown, and hybrid approaches 17-19. The top-down method is mainly a production-based accounting approach and is extremely useful for quantifying energy flows between regions and countries 4. Although the top-down method requires less time and labor, it is not suitable for carbon accounting of small systems. The bottom-up method is used for a consumption-based accounting method, which is based on resource consumption at each step of human activity and life cycle analysis (LCA) 4. The bottom-up method has a relatively high accuracy, but time-consuming and requires a large amount of data 4. The hybrid method includes the synthesis of bottom-up