EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Observationally Constrained Cloud Phase Unmasks Orbitally Driven Climate Feedbacks

Lily Hahn1, Navjit Sagoo2, Trude Storelvmo3, Ivy Tan4, James Danco5, Bryan Raney5, and Anthony Broccoli5
Lily Hahn et al.
  • 1Department of Atmospheric Sciences, University of Washington
  • 2Department of Meteorology, University of Stockholm
  • 3Department of Geosciences, University of Oslo
  • 4Department of Atmospheric and Oceanic Sciences, McGill University
  • 5Department of Environmental Sciences, Rutgers, The State University of New Jersey

The mechanisms that amplify orbitally-driven changes in insolation and drive the glacial cycles of the past 2.6 million years, the Pleistocene, are poorly understood. Previous studies indicate that cloud-phase feedbacks oppose ice sheet initiation when orbital configuration supports ice sheet growth. Cloud phase was observationally constrained in a recent study and provides evidence for a weaker negative cloud feedback in response to carbon dioxide doubling. We observationally constrain cloud phase in the Community Earth System Model and explore how changes in orbital configuration impact the climate response. Constraining cloud phase weakens the negative high latitude cloud phase feedback and unmasks positive water vapor and cloud feedbacks (amount and optical depth) that extend cooling to lower latitudes. Snowfall accumulation and ablation metrics also support ice sheet expansion as seen in proxy records. This indicates that well-known cloud and water vapor feedbacks are the mechanisms amplifying orbital climate forcing.

How to cite: Hahn, L., Sagoo, N., Storelvmo, T., Tan, I., Danco, J., Raney, B., and Broccoli, A.: Observationally Constrained Cloud Phase Unmasks Orbitally Driven Climate Feedbacks, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16726,, 2023.