Effects of explicit atmospheric convection at high CO2

• Published in: Proceedings of the National Academy of Sciences
• Main Authors: Arnold, Nathan P., Branson, Mark, Burt, Melissa A., Abbot, Dorian S., Kuang, Zhiming, Randall, David A., Tziperman, Eli
• Format: Article in Journal/Newspaper
• Language: English
• Published: National Academy of Sciences 2014
• Subjects: Arctic; Climate change; Sea ice
• Online Access: http://nrs.harvard.edu/urn-3:HUL.InstRepos:41384983; https://doi.org/10.1073/pnas.1407175111

The 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. Version of Record