Estimation of national and provincial carbon emissions, terrestrial carbon sinks and their relative contribution to emission reductions during 1980~2020

<p indent="0mm">Global climate change, largely caused by anthropogenic carbon (C) emissions, has been one of the most critical challenges for human society. Reducing fossil fuel C emissions, enhancing the production and utilization of clean energy, as well as strengthening the terrestrial C sinks, are basic pathways for climate change mitigation and C neutrality target. To better support the formulation and the achievement of long-term mitigation pathway for China, this study conducted a systematic assessment of fossil fuel C emissions, emission reductions from clean energy usage, and terrestrial ecosystem C sinks at both national and provincial levels during the past four decades (1980~2020). Additionally, it evaluated the contributions of clean energy and terrestrial C sinks in mitigating C emissions and achieving relative emission reductions (referred to as “emission reduction contribution”, which can be considered a measure of C neutrality status). The results showed that at the national level, both total and per capita C emission increased significantly from 1980 to 2020, while C intensity per unit of GDP witnessed a notable decrease. Similar temporal trends were found in most provinces, though variations in the patterns of emission and relevant characteristics were evident among regions. Following the rapid deployment of clean energy, it has contributed to an emission reduction by approximately to ~20% of national total C emissions in 2020, while the contribution differed substantially by province due to differences in clean energy availability. China’s terrestrial ecosystems functioned as a sizable and increasing C sink, offsetting 15.1% of anthropogenic C emissions during 1980s~2010s. However, the emission reduction contribution of terrestrial ecosystem C sinks (i.e., the ratio of C sinks to C emissions) declined from 30.5% in the 1980s to 12.9% in the 2010s, mainly due to faster growth of C emission compared to the enhancement of C sinks. The size of terrestrial ecosystem C sinks varied substantially among provinces, with the largest sink in Inner Mongolia and the smallest in Shanghai. The average C sink per unit area is <sc>0.22 t C</sc>/(ha yr) during 1980~2020 at national level, with provincial values ranging between 0.04 (Qinghai)~0.68 (Fujian) t C/(ha yr). Our results highlight the following strategic focus areas for formulating long-term mitigation efforts. Improving energy efficiency should be prioritized across the country. Meanwhile, efforts to further explore clean energy potential and sustainable deployment should be strengthened in all provinces to achieve energy system decarbonization. Provincial strategies should also accommodate differing peak C emission timelines. Furthermore, the “three-optimal principles” for ecosystems management—optimizing vegetation goals by region, optimizing species combinations for a given site, and optimizing management for ecosystems based on their characteristics—are crucial to realizing the full potential in China’s terrestrial C sequestration.