The Accelerating Land Carbon Sink of the 2000s May Not Be Driven Predominantly by the Warming Hiatus

Abstract

Recent studies attributed the accelerating land carbon sink (SLAND) 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 SLAND 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 conceptual 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 SLAND. Instead, the roles of alternative drivers on the accelerating SLAND seem to be important.

Have Synergies Between Nitrogen Deposition and Atmospheric CO2 Driven the Recent Enhancement of the Terrestrial Carbon Sink?

“…Our analysis suggests that climate variations weakened the carbon sink over the recent period. The response of the biosphere to recent variations in climate is, however, uncertain with conflicting conclusions about the magnitude of change in the post‐2000 carbon sink (Ballantyne et al, ; Zhu et al, ).…”

“…The findings of this study are contrary to the conclusions of Ballantyne et al (), who argue that relatively cool surface temperatures (over 1998–2012—warming hiatus) reduced soil respiration, inducing a carbon sink. However, this warming hiatus hypothesis itself has been called into question because the changes in seasonal land sink trends between warming (1982–1998) and hiatus (1998–2014) periods do not match the changes in seasonal temperature trends (Zhu et al, ), and so changes in seasonal temperature are unlikely to be drivers of reduced annual ecosystem respiration. Thus, following contradictory studies, the mechanism(s) behind the increased terrestrial carbon sink since 2000 remain elusive.…”

Lower land-use emissions responsible for increased net land carbon sink during the slow warming period

“…Keenan et al 1 suggest increasing photosynthesis and decreased respiration, whereas Ballantyne et al 2 suggest decreasing photosynthesis and thus reduced respiration being the only mechanism through which RLS increased during the hiatus. Furthermore, the seasonal and spatial patterns of changes in land carbon sink do not match with those of temperature changes 17 . Of note is the fact that systematic errors in land use emissions 7 directly transfer as bias of RLS 5,18 .…”

Towards a feasible and representative pan-African research infrastructure network for GHG observations

“…Although significant knowledge has been derived from specific African regions such as Kenya (i.e. Arias-Navarro et al 2016, Jacobs et al 2017, Ortiz-Gonzalo et al 2018, Owuor et al 2018, there is a general lack of ground-based observations to constrain both continental (Valentini et al 2014) and global GHG budgets (Marcolla et al 2017, Zhu et al 2018.…”