Uncertainty in climate–carbon-cycle projections associated with the sensitivity of soil respiration to temperature

Carbon-cycle feedbacks have been shown to be very important in predicting climate change over the next century, with a potentially large positive feedback coming from the release of carbon from soils as global temperatures increase. The magnitude of this feedback and whether or not it drives the terrestrial carbon cycle to become a net source of carbon dioxide during the next century depends particularly on the response of soil respiration to temperature. Observed global atmospheric CO₂ concentration, and its response to naturally occurring climate anomalies, is used to constrain the behaviour of soil respiration in our coupled climate—carbon-cycle GCM. This constraint is used to quantify some of the uncertainties in predictions of future CO₂ levels. The uncertainty is large, emphasizing the importance of carbon-cycle research with respect to future climate change predictions.