01 December 2016

Climate Feedback Variance and the Interaction of Aerosol Forcing and Feedbacks

Science

Aerosols can influence cloud radiative effects and may alter interpretation of how Earth’s radiative budget responds to climate forcing. Three ensemble experiments with CESM using different greenhouse gas and aerosol scenarios are used to analyze the role of aerosols in climate feedbacks and their spread.

Impact

The standard deviation of feedbacks across ensemble members is small, typically 0.02 W m−2 K−1. Feedbacks from high (8.5 W m−2) and moderate (4.5 W m−2) radiative forcing cases are nearly identical. An aerosol kernel is introduced to remove effects of aerosol-cloud interactions that contaminate estimates of cloud feedbacks. Adjusted cloud feedbacks indicate an “aerosol feedback” due to increased sea-salt emissions, mostly in the Southern Ocean.

Summary

These two effects are also seen in aquaplanet simulations with varying fixed drop number. Thus aerosols can be a significant modifier of cloud feedbacks, and different representations of aerosols and their interactions with clouds may contribute to multimodel spread in climate feedbacks and climate sensitivity in multimodel archives.

 

Contact
Brian Medeiros
National Center for Atmospheric Research (NCAR)