Radiocarbon constraints imply reduced carbon uptake by soils during the 21st century

• DOI: 10.1126/science.aad4273
• Publication Date: 2016-09-22T18:38:11Z
• Authors: Yujie He; Susan E. Trumbore; Margaret S. Torn; Jennifer W. Harden; Lydia J. S. Vaughn; Steven D. Allison; James T. Randerson
• Keywords: Agricultural; 550; Life on Land; General Science & Technology; Forestry Sciences; Veterinary and Food Sciences; Biological Sciences; 15. Life on land; 01 natural sciences; 333; 13. Climate action; Environmental Sciences; 0105 earth and related environmental sciences

Soil is the largest terrestrial carbon reservoir and may influence the sign and magnitude of carbon cycle–climate feedbacks. Many Earth system models (ESMs) estimate a significant soil carbon sink by 2100, yet the underlying carbon dynamics determining this response have not been systematically tested against observations. We used 14 C data from 157 globally distributed soil profiles sampled to 1-meter depth to show that ESMs underestimated the mean age of soil carbon by a factor of more than six (430 ± 50 years versus 3100 ± 1800 years). Consequently, ESMs overestimated the carbon sequestration potential of soils by a factor of nearly two (40 ± 27%). These inconsistencies suggest that ESMs must better represent carbon stabilization processes and the turnover time of slow and passive reservoirs when simulating future atmospheric carbon dioxide dynamics.