Uncertain Changes of Vegetation Greenness Interannual Variability on Half of the Global Vegetated Surface

Abstract

Changes in the interannual variability (IAV) of vegetation greenness and carbon sequestration are key indicators of the stability and climate sensitivities of terrestrial ecosystems. Recent studies have examined the changes in the vegetation IAV using atmospheric CO2 observations and dynamic global vegetation models (DGVMs), however, reported different and even contradictory trends of IAV. Here, we investigate the changes in the IAV of vegetation greenness, quantified as coefficient of variability (CV), over the past few decades based on six long-term and three short-term satellite remote sensing products. Our results suggested that on half of the global vegetated surface, CV trends were uncertain (i.e., inconsistent CV trends when using different satellite remote sensing products). Meanwhile, we found that 22.20% and 28.20% of the global vegetated surface (i.e., mostly in the non-tropical land surface) show significant positive and negative CV trends (p ≤ 0.1), respectively. Regions with higher air temperature and greater aridity tend to have increasing CV trends, whereas greater vegetation greening trend and higher nitrogen deposition lead to smaller CV trends. Our study provides a remote sensing-based examination of the changes in the IAV of global vegetation greenness, and highlights the potential issues in studying the response of terrestrial ecosystems to climate change.