Carbonyl sulfide: a new tool for understanding the response of the land biosphere to climate change.

The global climate is changing mostly because of the anthropogenic emission of greenhouse gases, especially CO2, into the atmosphere. The rate of atmospheric CO2 growth in the future will depend on the balance between emissions and sink strengths. The importance of land photosynthesis in dampening the CO2 increase in the atmosphere is now well recognized and both climate and global carbon (C) models incorporate photosynthesis- climate feedbacks. However, we still lack robust tools for partitioning different component fluxes (e.g. photosynthesis, respiration, decomposition) and for assessing the effects of climate change and atmospheric CO2 increase on the C-sequestration potential of the biosphere. The paper by Stimler and coworkers in this issue of New Phytologist (pp. 869-878) shows that carbonyl sulfide (COS) represents a useful tracer of gross photosynthesis. This offers the perspective of an additional independent tool to study the terrestrial C cycle and to investigate ecosystem responses to global change.