Physics

Geology

Climate change

Meteorology

Cloud top

Cloud fraction

Shortwave

Lidar

Performance art

Cloud albedo

Atmospheric sciences

Operating system

Optics

Astronomy

Oceanography

International Satellite Cloud Climatology Project

Climate model

Satellite

Albedo (alchemy)

Coupled model intercomparison project

Programming language

Cloud cover

Computer science

Climatology

Art history

Reflection (computer programming)

Cloud computing

Environmental science

Remote sensing

Radiative transfer

Geophysical Research Letters

Over the Southern Ocean (SO, 40°S–70°S), climate models have consistently underestimated solar reflection. Here we evaluate the relationship between cloud profiles, cloud phase and radiation over the SO in Coupled Model Intercomparison Project Phase 6 (CMIP6) models against Clouds and the Earth's Radiant Energy System and Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations. We find that the lack of solar reflection is slightly improved in CMIP6 models compared to CMIP5's, attributable to a better representation of cloud fraction and phase. We show that clouds have a different vertical structure and radiative effect south and north of where the 0°C isotherm meets the surface (∼55°S). Although the models capture the greater vertical extent of clouds south of 55°S, they fail to reproduce the observed increase in solar reflection, which we pinpoint to cloud phase biases. Increasing CMIP6 supercooled liquid cloud opacity should help reduce their persistent shortwave biases.

Southern Ocean Solar Reflection Biases in CMIP6 Models Linked to Cloud Phase and Vertical Structure Representations