This is a companion to DOI:10.1029/2005GL025044.
Missing feedbacks, asymmetric uncertainties, and the underestimation of future warming
Article first published online: 26 MAY 2006
Copyright 2006 by the American Geophysical Union.
Geophysical Research Letters
Volume 33, Issue 10, May 2006
How to Cite
2006), Missing feedbacks, asymmetric uncertainties, and the underestimation of future warming, Geophys. Res. Lett., 33, L10703, doi:10.1029/2005GL025540., and (
- Issue published online: 26 MAY 2006
- Article first published online: 26 MAY 2006
- Manuscript Accepted: 24 MAR 2006
- Manuscript Revised: 17 MAR 2006
- Manuscript Received: 19 DEC 2005
 Historical evidence shows that atmospheric greenhouse gas (GhG) concentrations increase during periods of warming, implying a positive feedback to future climate change. We quantified this feedback for CO2 and CH4 by combining the mathematics of feedback with empirical ice-core information and general circulation model (GCM) climate sensitivity, finding that the warming of 1.5–4.5°C associated with anthropogenic doubling of CO2 is amplified to 1.6–6.0°C warming, with the uncertainty range deriving from GCM simulations and paleo temperature records. Thus, anthropogenic emissions result in higher final GhG concentrations, and therefore more warming, than would be predicted in the absence of this feedback. Moreover, a symmetrical uncertainty in any component of feedback, whether positive or negative, produces an asymmetrical distribution of expected temperatures skewed toward higher temperature. For both reasons, the omission of key positive feedbacks and asymmetrical uncertainty from feedbacks, it is likely that the future will be hotter than we think.