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Synte Peacock

1. Introduction An ensemble of climate simulations has been carried out using the Community Climate System Model, version 4 (CCSM4), which included a 1300-yr-duration 1850 preindustrial “control” run, six ensemble members of the twentieth-century climate (1850–2005), six ensemble members for the “low emissions” representative concentration pathway (RCP; RCP2.6) scenario, six ensemble members for the “medium-low emissions” (RCP4.5) scenario, six ensemble members for the “medium-high emissions

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C. M. Bitz, K. M. Shell, P. R. Gent, D. A. Bailey, G. Danabasoglu, K. C. Armour, M. M. Holland, and J. T. Kiehl

1. Introduction Equilibrium climate sensitivity (ECS) is an often used metric to evaluate the climate response to a perturbation in the radiative forcing. It is specifically defined as the equilibrium change in global mean surface air temperature that results from doubling the concentration of carbon dioxide (CO 2 ) in the atmosphere ( IPCC 1990 ). In this study we investigate how the new Community Climate System Model, version 4 (CCSM4) responds to doubling CO 2 compared to the previous

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Ernesto Muñoz, Wilbert Weijer, Semyon A. Grodsky, Susan C. Bates, and Ilana Wainer

the tropical Atlantic Ocean are analyzed, expanding on the CCSM3 analysis of the tropical Atlantic by Deser et al. (2006) and other CCSM3 studies. The model simulations, the observations, and the methodology used are described in section 2 . We provide some standard diagnostics for CCSM4 comparison to the CCSM3 and to observations, and evaluate how well the CCSM4 is able to simulate the tropical Atlantic seasonal cycle (in section 3 ), including the Atlantic warm pools. We then discuss how the

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Samuel Levis, Gordon B. Bonan, Erik Kluzek, Peter E. Thornton, Andrew Jones, William J. Sacks, and Christopher J. Kucharik

especially midwestern North America, where corn, soybean, and temperate cereals exist in higher concentrations than elsewhere. Past work has identified sensitive regions of potentially strong land–atmosphere coupling in North America (e.g., Koster et al. 2004 ). We do not address physical climate effects from crops on the global scale or in remote regions through teleconnections. From midwestern North America to the global scale we do evaluate the model’s simulation of carbon fluxes. Lokupitiya et al

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William H. Lipscomb, Jeremy G. Fyke, Miren Vizcaíno, William J. Sacks, Jon Wolfe, Mariana Vertenstein, Anthony Craig, Erik Kluzek, and David M. Lawrence

ice sheets in the CESM land surface component, the Community Land Model (CLM), along with infrastucture for coupling CLM to Glimmer-CISM ( Fig. 1 ). Work to date has focused on simulating and validating the SMB and steady-state geometry of the Greenland Ice Sheet as a step toward fully interactive ice sheet–climate modeling. This paper describes the model implementation and evaluates the ice sheet response to CESM surface forcing. Two companion papers ( Vizcaíno et al. 2013a , b ) analyze the GIS

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Christine A. Shields, David A. Bailey, Gokhan Danabasoglu, Markus Jochum, Jeffrey T. Kiehl, Samuel Levis, and Sungsu Park

performance statistics is presented to highlight the major cost savings associated with T31x3. This paper is not intended to be a comprehensive paper documenting all aspects of the T31x3 (or the FV2x1) simulation. Rather, it simply shows that the T31x3 is an alternative to the more costly FV2x1 by presenting a sample of basic climate state and variability metrics in comparison with available observations. 2. Model description and physics differences from standard CCSM4 CCSM4 is a fully coupled, global

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Richard B. Neale, Jadwiga Richter, Sungsu Park, Peter H. Lauritzen, Stephen J. Vavrus, Philip J. Rasch, and Minghua Zhang

( Peterson and Vose 1997 ). A comprehensive description of the observational datasets used is provided by NCAR's climate data guide ( http://climatedataguide.ucar.edu/ ). 4. Dominant impacts of individual model changes a. Finite volume dynamical core Lauritzen et al. (2010) carefully compare the performance of CAM3 and CAM4 dynamical cores in dry idealized experiments. However, it is difficult to directly address the impact on the climate simulation of changing from the spectral to the FV dynamical core

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Alicia R. Karspeck, Steve Yeager, Gokhan Danabasoglu, Tim Hoar, Nancy Collins, Kevin Raeder, Jeffrey Anderson, and Joseph Tribbia

in NHT between the equator and 30°N. This highlights the danger of using metrics that rely on correctly simulating the currents and temperatures of the abyssal ocean, where there are almost no observations, as a means of evaluating model or assimilation performance. The DWBC, which carries cold, recently ventilated waters from the far North Atlantic down the coast of North America, is thought to be the primary pathway of the deep southward flow of the overturning circulation. Modeling studies

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Jennifer E. Kay, Marika M. Holland, Cecilia M. Bitz, Edward Blanchard-Wrigglesworth, Andrew Gettelman, Andrew Conley, and David Bailey

. 4. Discussion This study explains the equilibrium Arctic response to increased greenhouse gases in climate models with different atmospheric components (CAM4, CAM5) and different degrees of ocean coupling (mixed layer ocean, full-depth ocean). The main strengths of this study are that it evaluates all factors thought to be important to the modeled Arctic 2 × CO 2 climate response and that it isolates the influence of atmospheric physics and ocean model complexity. The most significant finding

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C. Kendra Gotangco Castillo, Samuel Levis, and Peter Thornton

applications. More broadly, this study proposes an approach for comparing the effects of interactive nitrogen versus dynamic vegetation. Although certain results from the present evaluation are model specific, this approach can be used in other intercomparison studies to draw more general conclusions regarding the performance of carbon-only models versus models with interactive carbon and nitrogen, or models with static versus dynamic vegetation. Acknowledgments Computing resources were provided by the Oak

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