Influencing factors of carbon emission intensity and spatiotemporal heterogeneity in shrinking region of Northeast China’s three provinces during 2005–2023

Introduction Global warming is progressing, and China is under great pressure to reduce carbon dioxide emissions. The three northeastern provinces belong to the country’s powerful industry regions. They not only produce a large amount of carbon emissions but also suffer from city shrinkage. These two facts strongly indicate that China should progress toward low-carbon development. Methods Using data from the province-level cities in the three northeastern provinces in 2005, 2010, 2015, 2020, and 2023, this study explores their city shrinkage and carbon emission intensity spatial and time frames, and further explores how urban shrinkage affects the mechanisms of carbon emission intensity. Results Results show that core cities have little contraction and some are even still growing, while edge cities face stronger contraction. Over time, the overall level of contraction has gradually weakened. From 2005 to 2023, the average carbon emission intensity decreased from 4.54 to 2.87, with the standard deviation narrowing from 3.25 to 1.86. Regions with higher economic development generally showed a downward trend in carbon emission intensity, while resource-based cities showed more fluctuations. The relationship between urban shrinkage and carbon emission intensity in the three northeastern provinces improved each year but differed across regions, presenting a spatial pattern of high coordination in core cities and low coordination in peripheral areas. Among the influencing factors, GDP had a clear positive effect on carbon emission intensity with the highest explanatory power ( q = 0.404). The shares of human capital and per capita road area showed big spatial and temporal differences in their effects on carbon emissions, where the inhibitory effect of human capital gradually diminished and the promoting effect of road area intensified. Discussion This study provides theoretical references and decision-making support for formulating differentiated low-carbon planning strategies and achieving high-quality revitalization in old industrial bases facing urban shrinkage.