Earth & Environmental Sciences

As the second-largest terrestrial carbon (C) flux, soil respiration (R_S) has been stimulated by climate warming. However, the magnitude and dynamics of such stimulations of soil respiration are highly uncertain at the global scale, undermining our confidence in future climate projections. Here, we present an analysis of global R_S observations from 1987-2016. R_S increased (P < 0.001) at a rate of 27.66 g C m^-2 yr^-2 (equivalent to 0.161 Pg C yr^-2) in 1987-1999 globally but became unchanged in 2000-2016, which were related to complex temporal variations of temperature anomalies and soil C stocks. However, global heterotrophic respiration (R_h) derived from microbial decomposition of soil C increased in 1987-2016 (P < 0.001), suggesting accumulated soil C losses. Given the warmest years on records after 2015, our modeling analysis shows a possible resuscitation of global R_S rise. This study of naturally occurring shifts in R_S over recent decades has provided invaluable insights for designing more effective policies addressing future climate challenges.