Projected soil carbon loss with warming in constrained Earth system models

Area of Science:

• Earth System Science
• Climate Science
• Soil Science

Background:

• Soil carbon-climate feedback is a major uncertainty in global warming projections.
• Understanding soil carbon turnover is crucial for accurate climate modeling.

Purpose of the Study:

• To analyze intrinsic soil carbon turnover times across different biomes.
• To evaluate the accuracy of Earth system models in simulating soil carbon dynamics.
• To project the future role of soils in the global carbon cycle.

Main Methods:

• Assembled data from long-term, temperature-controlled soil incubation studies.
• Compared empirical turnover times with Earth system model estimations.
• Quantified potential carbon loss from soils under various emission scenarios.

Main Results:

• Arctic and boreal soils exhibit the shortest intrinsic carbon turnover times; tropical forests have the longest.
• Earth system models overestimate intrinsic soil carbon turnover time by 30% on average.
• Soils are projected to shift from a carbon sink to a source, losing 0.22–0.53 PgC/year by 2100.

Conclusions:

• Global soils are likely to exert a strong positive feedback on warming.
• This soil carbon feedback significantly reduces the remaining carbon budget for 1.5°C and 2°C targets.
• Climate change mitigation will be considerably more challenging due to soil carbon dynamics.