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Internal Variability and Disequilibrium Confound Estimates of Climate Sensitivity From Observations
Author(s) -
Marvel Kate,
Pincus Robert,
Schmidt Gavin A.,
Miller Ron L.
Publication year - 2018
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 - 10.1002/2017gl076468
Subject(s) - climate sensitivity , coupled model intercomparison project , climate model , climatology , environmental science , disequilibrium , radiative forcing , forcing (mathematics) , atmospheric sciences , proxy (statistics) , climate change , cloud feedback , geology , oceanography , medicine , machine learning , computer science , ophthalmology
An emerging literature suggests that estimates of equilibrium climate sensitivity (ECS) derived from recent observations and energy balance models are biased low because models project more positive climate feedback in the far future. Here we use simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to show that across models, ECS inferred from the recent historical period (1979–2005) is indeed almost uniformly lower than that inferred from simulations subject to abrupt increases in CO 2 radiative forcing. However, ECS inferred from simulations in which sea surface temperatures are prescribed according to observations is lower still. ECS inferred from simulations with prescribed sea surface temperatures is strongly linked to changes to tropical marine low clouds. However, feedbacks from these clouds are a weak constraint on long‐term model ECS. One interpretation is that observations of recent climate changes constitute a poor direct proxy for long‐term sensitivity.