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Missing feedbacks, asymmetric uncertainties, and the underestimation of future warming
Author(s) -
Torn Margaret S.,
Harte John
Publication year - 2006
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2005gl025540
Subject(s) - greenhouse gas , gcm transcription factors , environmental science , climatology , climate change , global warming , general circulation model , atmospheric sciences , range (aeronautics) , climate sensitivity , climate model , geology , oceanography , materials science , composite material
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 CO 2 and CH 4 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 CO 2 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.