###### Abstract  
Global climate change has significantly affected terrestrial carbon sinks. Net ecosystem production (NEP) plays a critical role in the global carbon cycle. However, interannual variability (IAV) of the NEP and its regional contributions and climate attributions are not well-understood on a global scale. This study used a diagnostic model driven by remote sensing leaf area index (LAI) to investigate the NEP IAV and analyze regional and climate contributions on a global scale from 1982 to 2016. We found large NEP IAV during the study period, with the NEP detrended anomaly ranging from \(-\)2.3 Pg C in 1998 to 1.6 Pg C in 2013 at a global scale. Furthermore, 63.7% and 34.1% of the areas showed positive and negative contributions to NEP IAVs globally, respectively. Evergreen broadleaf forest (EBF) contributed the most (31.1%) to NEP IAV, followed by cropland (21.7%) and grassland (20.8%). Temperature played the most critical roles in the global NEP IAV, with a contribution of 45.5%. However, the partial correlation between NEP and temperature was negative, and the correlation with precipitation was positive in most areas of the globe, indicating that global warming is not conducive to the global carbon sink, but abundant rainfall is important for the global carbon cycle. This study suggests that, to increase the global carbon sink, we should pay more attention to tropical forests (EBFs) and highlight the importance of water availability. global climate change; interannual variability (IAV); net ecosystem production; regional contribution; climate attribution +
Footnote †: journal: Remote Sensing  
0000-0001-939X/0000-00001-939X/00000-00001-939X/00000-00001-939X/00000-00001-939X/0000001-939X/000001-939X/000001-939X/00001-939X/000001-939X/000001-93  
Global land carbon sink has had a significant upward trend over recent decades, but shows large IAV [1; 9]. Global climate change and climate variability could influence related physiological and biogeochemical processes and significantly affect the IAV of global NEP [10; 11; 12]. For example, warmer temperatures could promote plant growth and thus could be regarded as one main reason for enhanced vegetation productivity over northern higher latitudes [13; 14]. Photosynthesis could sharply drop off when an ecosystem becomes water-limited [15]. However, there is still a lack of studies on the climate factors' attribution on the IAV of NEP at a global scale. For mitigating global warming, regions dominating the global NEP are more effective for carbon uptake on a long-time scale [16]. Investigating the IAV of global NEP and exploring regional contributions are of great significance for ecosystem management and climate policymaking [17]. Studying global and regional IAV of NEP relies on ecosystem models. Terrestrial biosphere models can be classified into two main types depending on how leaf area index (LAI) is obtained: diagnostic and prognostic models [18]. Prognostic models use climatic and graphic conditions to simulate vegetation structure and the carbon cycle [1]. However, the simulated results have varied in prognostic models [19]. The biggest uncertainty of the prognostic models is in simulating temporal variations in vegetation structural parameters such as LAI. Compared to simulating LAI by the prognostic model, LAI based on satellite observations can better reflect the changes in vegetation growth. Diagnostic models that use remotely sensed LAI are effective tools to simulate the global historic carbon dynamics [20]. The Boreal Ecosystem Productivity Simulator (BEPS) is a diagnostic model driven by remote sensing LAI, and could perform better than the prognostic model in simulating the carbon sink for long-time series and large regional scale in the past [20]. The BEPS model has been adopted for all ecosystems over the globe [21; 22]. Here, we used the BEPS model to simulate spatiotemporal variations in global terrestrial ecosystems' NEP and investigate their regional contributions and climate attributions during 1982-2016.