The Accelerating Land Carbon Sink of the 2000s May Not Be Driven Predominantly by the Warming Hiatus
Geophysical Research Letters
Recent studies attributed the accelerating land carbon sink (S LAND ) during the 2000s to respiration decrease induced by the warming hiatus. We used two long-term atmospheric inversions, three temperature data sets, and eight ecosystem models to test this attribution. Our results show that the changes in seasonal S LAND trend between the warming (1982-1998) and hiatus (1998-2014) periods do not track evidently the changes in seasonal temperature trends at both global and regional scales. A
... eptual model of the annual/seasonal temperature response of respiration suggests that changes in seasonal temperature during this period are unlikely to cause a significant decrease in annual respiration. The ecosystem models suggest that trends in both gross primary production and terrestrial ecosystem respiration slowed down slightly, but the resulting slight acceleration in net ecosystem productivity is insufficient to explain the increasing trend in S LAND . Instead, the roles of alternative drivers on the accelerating S LAND seem to be important. Plain Language Summary Understanding the mechanisms controlling changes in the land carbon sink is of great importance for projecting future climate. Recent studies attributed the accelerating land sink during the 2000s to the respiration decrease induced by the warming hiatus. By analyzing changes in seasonal and regional trends in the observed CO 2 fluxes and temperature, we show that the seasonal/spatial trend changes of temperature are not consistent with patterns of the land sink. The ecosystem model simulations also suggest that the slight increase in terrestrial ecosystem carbon sink cannot explain the significant enhancement of land sink during the warming hiatus. These results collectively showed that the warming hiatus could not explain the accelerating land sink and other processes should be reevaluated.