Abstract Aerosol‐cloud interactions (ACI) in warm clouds are the primary source of uncertainty in effective radiative forcing (ERF) during the historical period and, by extension, inferred climate sensitivity. The ERF due to ACI (ERFaci) is composed of the radiative forcing due to changes in cloud microphysics and cloud adjustments to microphysics. Here, we examine the processes that drive ERFaci using a perturbed parameter ensemble (PPE) hosted in CAM6. Observational constraints on the PPE result in substantial constraints in the response of cloud microphysics and macrophysics to anthropogenic aerosol, but only minimal constraint on ERFaci. Examination of cloud and radiation processes in the PPE reveal buffering of ERFaci by the interaction of precipitation efficiency and radiative susceptibility.
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Radiative and Precipitation Processes Make it Easier to Match the Temperature Record and Harder to Constrain Future Warming
Abstract By examining the historical temperature record during the industrial era, we can infer the climate's sensitivity to radiative perturbations, given knowledge of historical forcings. Energy conservation enforces a negative correlation between the climate feedback and historical forcing for a given change in global‐mean temperature. Here, we examine the negative correlation between the radiative forcing due to aerosol‐cloud interactions and the shortwave cloud feedback to warming that appears in a perturbed parameter ensemble (PPE). The PPE is not tuned to match the historical record, yet a negative correlation emerges over the extratropics due to the combined effects of liquid cloud precipitation efficiency and radiative saturation in the shortwave. Using an energy balance model, we argue that these processes combine to push Earth System Models to yield a temperature record in keeping with observations, but also limit our ability to constrain future warming posterior with the temperature record.
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- Award ID(s):
- 2441832
- PAR ID:
- 10662875
- Publisher / Repository:
- Geophysical Research Letters
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 52
- Issue:
- 24
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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