Mapping carbon sinks in megacity ecosystem: accuracy estimation coupling experiment and satellite data based on GEE

Accurate monitoring of carbon sinks at individual, community, green space, and urban scales is critical to understanding and modeling urban ecosystem carbon balance and their sensitivity to climate change. However, research results of different sizes and scales differ greatly, resulting in difficulties in the measurement and accounting of carbon sinks. Take the experimental data as the standard value, the scale effect of multi-source remote sensing data in the improved Carnegie–Ames–Stanford approach was analyzed, and the data meeting the best spatial analysis was selected to realize month-by-month dynamic monitoring of carbon sinks from city, district and park scales. Based on the comparison of Google earth engine calculation and sample measurement, the accuracy of carbon sinks was obtained. The study concluded that: (1) Tianjin’s carbon sink is highest in the northwest, decreasing towards the central city and Binhai New Area. (2) Tianjin’s highest carbon sink (11.78–22.69 g/m²) is in September, and its lowest (0.36–0.83 g/m²) in February. (3) The accuracy for the 10 m scale is around − 10%, the 30 m scale is − 90%, and the 250 m scale is more than − 99%. Based on the comparative analysis under different space sizes, this study quantifies the error range, which can contribute to the accurate quantization of green space cross-scale research and support multi-scale urban green space planning.