Insights from a Refined Decomposition of Cloud Feedbacks

TitleInsights from a Refined Decomposition of Cloud Feedbacks
Publication TypeJournal Article
Year of Publication2016
AuthorsZelinka, Mark D., Zhou Chen, and Klein Stephen A.
JournalGeophys. Res. Lett.
Abstract / Summary

Decomposing cloud feedback into components due to changes in several gross cloud properties provides valuable insights into its physical causes. Here we present a refined decomposition that separately considers changes in free tropospheric and low cloud properties, better connecting feedbacks to individual governing processes and avoiding ambiguities present in a commonly-used decomposition. It reveals that three net cloud feedback components are robustly nonzero: positive feedbacks from increasing free tropospheric cloud altitude and decreasing low cloud cover and a negative feedback from increasing low cloud optical depth. Low cloud amount feedback is the dominant contributor to spread in net cloud feedback, but its anti-correlation with other components damps overall spread. The ensemble mean free tropospheric cloud altitude feedback is roughly 60% as large as the standard cloud altitude feedback because it avoids aliasing in low cloud reductions. Implications for the “null hypothesis” climate sensitivity from well-understood and robustly-simulated feedbacks are discussed.

URLhttp://dx.doi.org/10.1002/2016GL069917
DOI10.1002/2016gl069917
Journal: Geophys. Res. Lett.
Year of Publication: 2016

Decomposing cloud feedback into components due to changes in several gross cloud properties provides valuable insights into its physical causes. Here we present a refined decomposition that separately considers changes in free tropospheric and low cloud properties, better connecting feedbacks to individual governing processes and avoiding ambiguities present in a commonly-used decomposition. It reveals that three net cloud feedback components are robustly nonzero: positive feedbacks from increasing free tropospheric cloud altitude and decreasing low cloud cover and a negative feedback from increasing low cloud optical depth. Low cloud amount feedback is the dominant contributor to spread in net cloud feedback, but its anti-correlation with other components damps overall spread. The ensemble mean free tropospheric cloud altitude feedback is roughly 60% as large as the standard cloud altitude feedback because it avoids aliasing in low cloud reductions. Implications for the “null hypothesis” climate sensitivity from well-understood and robustly-simulated feedbacks are discussed.

DOI: 10.1002/2016gl069917
Citation:
Zelinka, MD, C Zhou, and SA Klein.  2016.  "Insights from a Refined Decomposition of Cloud Feedbacks."  Geophys. Res. Lett..  https://doi.org/10.1002/2016gl069917.