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Updated: Jul 9, 2025

Measuring Carbon-based Contaminant Mineralization Using Combined CO2 Flux and Radiocarbon Analyses
Published on: October 21, 2016
State dependence of CO2 forcing and its implications for climate sensitivity
Haozhe He1, Ryan J Kramer2,3, Brian J Soden1
1Rosenstiel School of Marine, Atmospheric and Earth Science, University of Miami, Miami, FL, USA.
Instantaneous radiative forcing from carbon dioxide (CO2) doubling is not constant. Its dependence on the climate base state, particularly stratospheric cooling, impacts climate sensitivity and model discrepancies.
Area of Science:
- Climate science
- Atmospheric physics
- Radiative transfer
Background:
- Current climate models assume constant instantaneous radiative forcing (IRF) for CO2 doubling.
- Variations in climate sensitivity are attributed to radiative feedbacks and their base-state dependence.
Purpose of the Study:
- To investigate the assumption of constant IRF.
- To determine the impact of base-state dependence on IRF and climate sensitivity.
- To explain intermodel spread in climate sensitivity.
Main Methods:
- Analysis of radiative forcing calculations.
- Examination of climate model outputs.
- Assessment of base-state effects on IRF.
Main Results:
- IRF is not constant; it depends on the climatological base state.
- IRF increases by ~25% per CO2 doubling.
- IRF has risen ~10% since the preindustrial era due to stratospheric cooling.
- Base-state dependence explains ~50% of intermodel spread in IRF.
Conclusions:
- The non-constant nature of IRF challenges existing climate sensitivity assumptions.
- Stratospheric cooling is a key factor influencing IRF and climate sensitivity.
- Addressing base-state dependence is crucial for reducing climate model uncertainty.
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