Multiple greenhouse-gas feedbacks from the land biosphere under future climate change scenarios

• Published in: Nature climate change 2013-07, Vol.3 (7), p.666-672
• Main Authors: Stocker, Benjamin D., Roth, Raphael, Joos, Fortunat, Spahni, Renato, Steinacher, Marco, Zaehle, Soenke, Bouwman, Lex, Xu-Ri, Prentice, Iain Colin
• Format: Article
• Language: English
• Subjects: 704/106/35; 704/158; Albedo; Animal and plant ecology; Animal, plant and microbial ecology; Anthropogenic factors; Biological and medical sciences; Biosphere; Carbon cycle; Carbon dioxide; Climate Change; Climate Change/Climate Change Impacts; Climatology. Bioclimatology. Climate change; Earth, ocean, space; Environment; Environmental Law/Policy/Ecojustice; Exact sciences and technology; External geophysics; Fundamental and applied biological sciences. Psychology; Greenhouse gases; Land use; letter; Meteorology; Methane; Synecology; Terrestrial ecosystems; Terrestrial environments
• ISSN: 1758-678X; 1758-6798
• DOI: 10.1038/nclimate1864

The sensitivity of the terrestrial biosphere to changes in climate constitutes a feedback mechanism with the potential to accentuate global warming. Process-based modelling experiments now indicate that under a business-as-usual emissions scenario the biosphere on land is expected to be an increasingly positive feedback to anthropogenic climate change, potentially amplifying equilibrium climate sensitivity by 22–27%. Atmospheric concentrations of the three important greenhouse gases (GHGs) CO 2 , CH 4  and N 2 O are mediated by processes in the terrestrial biosphere that are sensitive to climate and CO 2 . This leads to feedbacks between climate and land and has contributed to the sharp rise in atmospheric GHG concentrations since pre-industrial times. Here, we apply a process-based model to reproduce the historical atmospheric N 2 O and CH 4  budgets within their uncertainties and apply future scenarios for climate, land-use change and reactive nitrogen (Nr) inputs to investigate future GHG emissions and their feedbacks with climate in a consistent and comprehensive framework 1 . Results suggest that in a business-as-usual scenario, terrestrial N 2 O and CH 4  emissions increase by 80 and 45%, respectively, and the land becomes a net source of C by AD 2100. N 2 O and CH 4  feedbacks imply an additional warming of 0.4–0.5 °C by AD 2300; on top of 0.8–1.0 °C caused by terrestrial carbon cycle and Albedo feedbacks. The land biosphere represents an increasingly positive feedback to anthropogenic climate change and amplifies equilibrium climate sensitivity by 22–27%. Strong mitigation limits the increase of terrestrial GHG emissions and prevents the land biosphere from acting as an increasingly strong amplifier to anthropogenic climate change.