title: Effects of explicit atmospheric convection at high CO2.
abstract: 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.
authors.affiliation: Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138; eli@eps.harvard.edu nathan@atmos.colostate.edu randall@atmos.colostate.edu.
authors.forename: Nathan P
authors.initials: NP
authors.lastname: Arnold
authors.affiliation: Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523;
authors.forename: Mark
authors.initials: M
authors.lastname: Branson
authors.affiliation: Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523;
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Burt
authors.affiliation: Department of Geophysical Sciences, The University of Chicago, Chicago, IL 60637; and.
authors.forename: Dorian S
authors.initials: DS
authors.lastname: Abbot
authors.affiliation: Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138;School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138.
authors.forename: Zhiming
authors.initials: Z
authors.lastname: Kuang
authors.affiliation: Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523; eli@eps.harvard.edu nathan@atmos.colostate.edu randall@atmos.colostate.edu.
authors.forename: David A
authors.initials: DA
authors.lastname: Randall
authors.affiliation: Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138;School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138 eli@eps.harvard.edu nathan@atmos.colostate.edu randall@atmos.colostate.edu.
authors.forename: Eli
authors.initials: E
authors.lastname: Tziperman
mesh_terms: D001110:Arctic Regions; D001272:Atmosphere; D002245:Carbon Dioxide; D057231:Climate Change; D007053:Ice; D008962:Models, Theoretical
chemical_list: D007053:Ice; D002245:Carbon Dioxide
keywords: climate projections; climate sensitivity; global warming