## 1 Introduction  
With the in-depth implementation of the new urbanization strategy, China's urbanization has entered a stage of rapid development. The urbanization rate reached 53.73% in 2013, which is close to the world average level, while there are still some gaps when compared with the developed countries with about 80% urbanization rate. The rapid acceleration of urbanization has caused increasingly serious ecological problems. As the world's largest carbon emitter, China has an inescapable responsibility in reducing carbon emissions [1]. To this end, the Chinese government has solemnly promised: by 2020, China's carbon emissions will be 40% to 45% lower than in 2005. This is also the responsibility of China as a responsible big country. Studying carbon emissions from the perspective of urbanization is not only conducive to the coordinated development of China's economy, population, resources, and environment, but it is also conducive to the scientific formulation of carbon emission reduction policies and the smooth realization of carbon emission reduction targets. Therefore, exploring the impact of urbanization on carbon emissions has important practical and theoretical implications. In view of this, this paper will locate the research area in the Yangtze River Delta urban agglomeration (all the administrative areas of Shanghai, Zhejiang, and Jiangsu, the specific situation is shown in Figure 1) and analyze how the path and difference in regional urbanization development affect carbon emissions, with a view of providing reference for China's new urbanization development and carbon emission reduction targets. Existing studies generally believe that the level of urbanization has an important impact on regional carbon emissions [2; 3]. Some scholars found that \"a linear relationship between urbanization and carbon emissions\" [4; 5], while some scholars believe that \"the direct relationship, between urbanization and carbon emissions, is not just a simple linear relationship. Urbanization has both driving and braking effects on carbon emissions\" [6; 7; 8]. When urbanization is in its infancy, the population of urban areas is growing rapidly. The proportion of the primary industry has gradually declined, the proportion of the secondary and tertiary industries has gradually increased, and people's lifestyles are also gradually becoming more carbonized [9; 10; 11]. At this time, the scale and the agglomeration effects of the towns have not yet formed, and the combination of these factors, the driving effect of urbanization on carbon emissions, is greater than that of the braking effect, which is reflected in the positive effect of urbanization on carbon emissions [12; 13; 14]. However, when urbanization develops to a certain level, the scale and agglomeration effects of urbanization and the effect of technology diffusion gradually appear. Together, these factors cause the braking effect of urbanization on carbon emissions to be greater than the driving effect, which is manifested in the negative impact of urbanization on carbon emissions. [15; 16; 17; 18]. Some scholars, such as [PERSON] and [PERSON]. [19], believe that the impact of urbanization on carbon emissions is insignificant. With the deepening of research, some scholars have gradually realized that there are still major obstacles to establish a clear and direct link between urbanization and carbon emissions. Because the impact of urbanization on carbon emissions is a complex issue that involves many levels, many other factors also impact on carbon emissions, which is the result of the combination of urbanization and other factors. Accordingly, most of the studies have combined urbanization with other relevant factors to examine its impact on carbon emissions--the combined effect.