Satellite measurements show that the Northern and Southern hemispheres reflect equal amounts of short-wave radiation (“albedo symmetry”), but no theory exists on if, how, and why the symmetry is established and maintained. Ambiguously, climate models are strongly biased in albedo symmetry but agree in the sign of the response to CO₂. We find that mean-state biases in albedo symmetry and surface temperature asymmetry correlate negatively. Similarly, the response of albedo asymmetry to CO₂ forcing correlates negatively with the magnitude of the asymmetry in surface warming. This is true across many and within single climate model simulations: a too warm or stronger warming hemisphere is darker or darkens more than its counterpart. In the 21 years of observations we find the same tendency and hypothesize a) albedo symmetry is a function of the current climate state and b) we will observe an evolution towards albedo asymmetry in coming decades.

The data is processed from standard model output from CMIP5 and CMIP6 models. These are freely available:

https://esgf-node.llnl.gov/search/cmip5/ 

https://esgf-node.llnl.gov/search/cmip6/

Definitions of acronyms can be found at: https://www.wcrp-climate.org/wgcm-cmip/wgcm-cmip6

The observed data are also freely availabe (just copied here) and documented:

Morice, C. P., and Coauthors, 2021: An Updated Assessment of Near-Surface Temperature Change From 1850: The HadCRUT5 Data Set. Journal of Geophysical Research: Atmospheres, 126 (3), e2019JD032 361, doi:https://doi.org/10.1029/2019JD032361.

Loeb, N. G., and Coauthors, 2020: New Generation of Climate Models Track Recent Unprecedented Changes in Earth’s Radiation Budget Observed by CERES. Geophysical Research Letters, 47 (5), e2019GL086 705, doi:10.1029/2019GL086705, URL https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL086705, e2019GL086705 2019GL086705