National clusters and carbon emissions based on “N + 3E” framework: insights from global carbon source and sink

In the global pursuit of carbon neutrality, nature’s unique ability to store carbon is often overlooked, despite its significant implications for achieving this goal. First, carbon sinks were measured using net primary productivity (NPP), and NPP was calculated for 70 major countries, using remotely sensed data. Next, the “N + 3E” system was developed to assess the interplay of carbon sinks, energy, economy, and environmental, and then used to cluster the countries accordingly. Finally, per capita carbon dioxide (CO₂) emissions trends for the resulting country clusters were analyzed using the Mann–Kendall model. The findings showed that: (1) Based on the “N + 3E” system, the 70 countries can be classified into five categories: high carbon sink—less developed countries (H-LDC), medium carbon sink—economy priority countries (M-EPC), high carbon sink—low carbon transition countries (H-LCTC), medium carbon sink—developed countries (M-DC),and low carbon sink—high energy consumption affluent countries (L-HECAC). (2) Carbon sink levels vary significantly across these categories: NPP is highest in H-LCTC, followed by H-LDC, then M-DC. M-EPC have the fourth-highest NPP, while L-HECAC have the lowest. (3) Energy affluence is 30, 94, 96, 100, and 100% for H-LDC, M-EPC, H-LCTC, M-DC, and L-HECAC, respectively. (4) Per capita carbon dioxide emissions of the five categories mentioned above increase sequentially, while emission trends exhibit the opposite pattern. The number of countries with decreasing CO₂ trend is zero for H-LDC, few for M-EPC, more for H-LCTC, and all for M-DC. This paper highlights the role of carbon sinks in different country types, offering insights for developing tailored emission reduction strategies.