Arnold, Nathan P.Branson, MarkBurt, Melissa A.Abbot, Dorian S.Kuang, ZhimingRandall, David A.Tziperman, Eli2019-09-222014Arnold, N. P., M. Branson, M. A. Burt, D. S. Abbot, Z. Kuang, D. A. Randall, and E. Tziperman. 2014. “Effects of Explicit Atmospheric Convection at High CO2.” Proceedings of the National Academy of Sciences 111 (30): 10943–48. https://doi.org/10.1073/pnas.1407175111.0027-84240744-28311091-6490http://nrs.harvard.edu/urn-3:HUL.InstRepos:41384983The effect of clouds on climate remains the largest uncertainty in climate change predictions, due to the inability of global climate models (GCMs) to resolve essential small-scale cloud and convection processes. We compare preindustrial and quadrupled CO2 simulations between a conventional GCM in which convection is parameterized and a "superparameterized" model in which convection is explicitly simulated with a cloud-permitting model in each grid cell. We find that the global responses of the two models to increased CO2 are broadly similar: both simulate ice-free Arctic summers, wintertime Arctic convection, and enhanced Madden-Julian oscillation (MJO) activity. Superparameterization produces significant differences at both CO2 levels, including greater Arctic cloud cover, further reduced sea ice area at high CO2, and a stronger increase with CO2 of the MJO.en-USJournal Article2019-09-2210.1073/pnas.1407175111