Background
The authors write that "ecosystem carbon (C) storage strongly regulates climate-C cycle feedback and is largely determined by both C residence time and C input from net primary productivity (NPP)." However, they indicate that "spatial patterns of ecosystem C storage and its variation have not been well quantified in earth system models (ESMs)," which failed feat is extremely significant, as its accomplishment is considered to be "essential to predict future climate change."

What was done
Yan et al. say they (1) "aimed to evaluate spatial variation in ecosystem C storage capacity simulated by ESMs included in CMIP5" and to (2) "examine sources of multi-model variability in the results associated with MRT [mean residence time] and/or C inputs."

What was learned
The four researchers report that (1) "model intercomparison indicated that NPP was simulated relatively well by most models", but that "MRT was substantially underestimated by most of the models," that (2) "underestimation of MRT resulted in lower estimates for ecosystem C storage capacity," and that (3) "large spatial variations in MRT and NPP resulted in large variations in ecosystem C storage capacity, particularly at high latitudes and in sparsely vegetated regions."

What it means
Yan et al. end their paper by saying their results "indicate that more research should be conducted in the future to estimate C partitioning and transfer coefficients among C pools so that ecosystem C residence time and storage capacity can be accurately simulated," which feat, as they note in the introduction to their study (and as we repeat here for emphasis), is considered to be "essential to predict future climate change."