随着我国经济从高速发展转向高质量发展，我国提出“加快构建以国内大循环为主体、国内国际双循环相互促进的新发展格局”，强调畅通国内生产、分配、流通、消费整个循环过程，提高国际循环质量，打通国内国际双循环衔接，推动我国经济高质量发展。与此同时，随着“双碳”目标的提出，我国在碳减排方面也面临着更大的挑战。城市是我国对外开放、参与国际循环的重要窗口，也是应对气候变化，实现双碳目标的关键。目前从价值链视角分析我国城市尺度隐含碳和增加值流动，解析国内地区在国内国际两个循环过程中的角色及相应的环境和社会经济影响的研究仍然缺失。在这样的背景下，本研究采用多区域投入产出模型、价值链研究框架、复杂网络等方法，分析内循环、外循环及内外双循环嵌入视角下的我国城市尺度的碳排放与增加值格局，解析国内大循环中的城市分工及其伴随的碳排放转移和增加值影响、我国参与外循环的主要方式及相应的碳排放和增加值、国内国际双循环嵌套对我国城市碳排放和增加值的影响。

本研究结果显示，城市间内循环对我国碳排放和增加值的贡献远超国际循环。我国城市间内循环过程中产生的碳排放和增加值在不同环节存在不同的地区间差异特征：产品生产阶段的隐含碳循环主要集中于北方地区，增加值主要集中于胡焕庸线以东地区；产品销售和使用阶段的隐含碳循环主要集中于华北、中部和南部地区，增加值则集中于长三角城市群及其周边，长三角城市群在我国内循环格局中扮演着重要角色。我国高收入城市的碳排放强度与前向价值链参与度之间存在显著正相关关系；中低收入城市的碳排放强度则与价值链前后向参与度均显著相关。国内循环产生的碳排放和增加值在不同部门之间存在巨大差异，大部分碳排放集中于传统制造业和电力热力的生产和供应两个部门，服务业对国内增加值的贡献高于其他所有部门的总和，但从最终产品拉动隐含碳和增加值循环的角度来看，建筑和服务业产品的主导作用更为明显。从国家尺度来看，我国参与外循环的主要方式是传统贸易，但是从城市尺度来看，我国在双循环格局中的隐含碳和增加值流出主要通过复杂价值链实现。我国最重要的贸易伙伴是美国，其次是欧盟，日韩和东南亚，长三角、珠三角、山东半岛和京津冀城市群是我国参与国际循环、实现国内国际循环嵌入的最主要地区。实现内外双循环嵌入的贸易路径对我国碳排放和增加值的贡献呈现增长趋势，主要通过复杂价值链实现。实现我国内外双循环嵌入的城市群拉动的国内碳排放和增加值流动大部分发生在城市群内部。双循环视角下国内城市的价值链参与度高于单纯国内循环视角下的参与度，内外双循环的嵌入拉动了我国城市参与地区间分工的程度。

基于上述结果，本研究建议我国各地区减排目标和措施的制定和实施应加强地区间协作，从降低碳足迹的角度促进全产业链的深度脱碳；深入促进通信电子设备、服务业等环境成本低、经济收益高的产业的发展，促进我国全球价值链地位的提升；加强与东盟地区的经贸往来与合作，同时注重国际出口和投资的低碳化、清洁化。

As China's economy shifts from high-speed development to high-quality development, Chinese government proposed to "accelerate the construction of a new development pattern with domestic circulation as the main part while domestic and international dual circulation promoting each other", emphasizing the unimpeded circulation of production, distribution, circulation and consumption. At the same time, with the carbon peaking and carbon neutrality goals proposed, China is also facing greater challenges in carbon emission reduction. Cities are important nodes for China to open up and participate in the international circulation, and they are also key to realizing the goal of carbon reduction. However, there is still a lack of city-scale research implied carbon flow in China which covers both domestic and international circulation processes. Therefore, this study adopts Multi-Regional Input-Output model, Global Value Chain framework, complex network and other methods to analyze the internal circulation pattern of carbon emissions and value added of Chinese cities, as well as the pattern of China's participation in the external circulation and the internal-external embedded circulation.

The results show that the contribution of domestic intra-city circulation to China's carbon emission and value added is far greater than that of international circulation. The carbon emissions and value added generated in the domestic circulation have different regional differences in different stage. The embodied carbon circulation of the production stage is mainly concentrated in the northern region, and the value added is mainly concentrated in the east of Hu Huanyong line. The embodied carbon circulation of product sales and use stage is mainly concentrated in North China, central and southern regions, while the value added is concentrated in the Yangtze River Delta city cluster and its surrounding areas. The Yangtze River Delta city cluster plays an important role in domestic circulation. There is a significant positive correlation between carbon emission intensity and forward value chain participation of high-income cities in China, while the carbon intensity of low - and middle-income cities is significantly correlated with both forward and backward participation in the value chain. The carbon emissions and value added of domestic circulation vary greatly among different sectors. Most of the carbon emissions are concentrated in the traditional manufacturing sector and the production and supply of electricity and heat sector, while the contribution of the service sector to domestic value added is higher than that of all other sectors combined. From the perspective of country scale, the main way of China's participation in external circulation is traditional trade, but from the perspective of city scale, the embodied carbon and value added outflow from Chinese cities is mainly realized through complex value chains. China's most important trading partner is the United States, followed by the European Union, Japan and South Korea, and Southeast Asia. The Yangtze River Delta, the Pearl River Delta, the Shandong Peninsula and the Beijing-Tianjin-Hebei city cluster are the most important regions in China that participate in the international circulation and realize the embedment of domestic and international circulation. Most of the intra-city embodied carbon and value added flow in China driven by export occurred in the exporting city cluster. The forward and backward participation of Chinese cities in the value chain from the perspective of dual circulation is higher than that from the perspective of simple domestic circulation, which means that the embedding of domestic and international circulation drives the participation of Chinese cities in the inter-regional division of labor.

Based on the results, this study suggests that the formulation and implementation of emission reduction targets and measures in various regions in China should strengthen regional cooperation, and promote the deep decarbonization of the whole industrial chain from the perspective of reducing carbon footprint. Promote the development of industries with low environmental costs and high economic returns, such as communications electronic equipment and service industries, which can also help the promotion of China's position in the global value chain. In addition, it is recommended to strengthen economic and trade exchanges and cooperation with Southeast Asia, while focusing on low-carbon and clean international exports and investment.