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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

of Shell et al. (2008) . We use the adjusted cloud radiative forcing to estimate cloud feedback following Soden et al. (2008) . The cloud component can be further broken down into shortwave and longwave feedbacks ( and ) according to their influence on Δ Q and Δ F separately. The same is true for λ w ; however, the shortwave component of the water vapor feedback is nearly always the same so the longwave component accounts for most of the range in λ w . Table 3 lists the global annual

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Esther C. Brady, Bette L. Otto-Bliesner, Jennifer E. Kay, and Nan Rosenbloom

λ LWCLR is reduced by positive feedbacks from longwave cloud forcing λ LWCF , shortwave clear-sky λ SWCLR , and shortwave cloud λ SWCF processes. These component feedbacks are computed as follows ( Table 5 ): The clear-sky longwave feedback (7a) has a similar magnitude for all simulations, and the longwave feedback from clouds (7b) is a relatively minor component. Thus, the longwave component feedbacks do not explain the smaller λ and hence higher sensitivity found in LGMCO 2

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Gijs de Boer, William Chapman, Jennifer E. Kay, Brian Medeiros, Matthew D. Shupe, Steve Vavrus, and John Walsh

. Bailey , 2012 : The influence of local feedbacks and northward heat transport on the equilibrium Arctic climate response to increased greenhouse gas forcing . J. Climate , in press . Klein , S. , and Coauthors , 2009 : Intercomparison of model simulations of mixed-phase clouds observed during the ARM mixed-phase arctic cloud experiment. Part I: Single-layer cloud . Quart. J. Roy. Meteor. Soc. , 135 , 979 – 1002 . Lawrence , D. , A. Slater , and S. Swenson , 2012 : Simulation of

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Gerald A. Meehl, Warren M. Washington, Julie M. Arblaster, Aixue Hu, Haiyan Teng, Jennifer E. Kay, Andrew Gettelman, David M. Lawrence, Benjamin M. Sanderson, and Warren G. Strand

2005 to 2100 produces a net positive forcing of between +0.8 and +1.2 W m −2 , removing most of the anthropogenic cooling. Further discussion of the regional effects of aerosols is given in section 5 below. Table 1. Table of estimates of radiative fluxes from atmosphere-only model experiments. For each RCP, shown are global mean estimates of the changes (Δ) between simulations with 2100 and 2005 emissions for cloud radiative effect (CRE), top-of-atmosphere (TOA) radiation change minus the net

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Semyon A. Grodsky, James A. Carton, Sumant Nigam, and Yuko M. Okumura

. , and Coauthors , 2006b : The formulation and atmospheric simulation of the Community Atmosphere Model version 3 (CAM3) . J. Climate , 19 , 2144 – 2161 . Compo , G. P. , and Coauthors , 2011 : The Twentieth Century Reanalysis Project . Quart. J. Roy. Meteor. Soc. , 137 , 1 – 28 . Cronin , M. F. , N. A. Bond , C. W. Fairall , and R. A. Weller , 2006 : Surface cloud forcing in the east Pacific stratus deck/cold tongue/ITCZ complex . J. Climate , 19 , 392 – 409 . Danabasoglu

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Keith Oleson

column and water is removed from each soil layer. Heat emissions produced by anthropogenic activities (wasteheat) are a contributor to the UHI. Globally this flux is small compared to greenhouse gas forcing, one estimate is that it is on the order of 0.03 W m −2 ( Flanner 2009 ), however, within cities it can be a significant and even dominant component of the local urban energy budget ( Ichinose et al. 1999 ). Sources of wasteheat include human metabolism, vehicles, commercial and residential

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David M. Lawrence, Keith W. Oleson, Mark G. Flanner, Christopher G. Fletcher, Peter J. Lawrence, Samuel Levis, Sean C. Swenson, and Gordon B. Bonan

model; the biogeophysical impact of transient land cover and land use change; the radiative forcing of aerosol deposition onto snow; terrestrial carbon fluxes and their evolution due to land use, wildfire, and net ecosystem production; the improved representation of permafrost; and the impact of prognostic vegetation state on climate variability. A discussion and summary of the strengths and weaknesses of the surface climate simulation within CCSM4 and ways in which CLM4 can be improved and expanded

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David M. Lawrence, Andrew G. Slater, and Sean C. Swenson

described and assessed in Gent et al. (2011) . For the twenty-first-century simulation, ensembles were completed for four different representative concentration projections (RCPs; Moss et al. 2010 ): RCP2.6, RCP4.5, RCP6.0, and RCP8.5, where the numerical value of each RCP indicates the approximate radiative forcing in the year 2100 (i.e., RCP8.5 has specified greenhouse gases and aerosol trajectories consistent with a radiative forcing of 8.5 W m −2 in the year 2100). The atmosphere and land

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Laura Landrum, Marika M. Holland, David P. Schneider, and Elizabeth Hunke

Antarctic sea ice variability and mean state in the absence of transient forcings, we analyze model output for 500 yr of a 1300-yr preindustrial integration (simulation years 701–1200 of the 1850 control run). The 1850 control run is a fully coupled land–ocean–ice–atmosphere run that is forced at constant 1850 conditions (constant trace gases, land use and plant functional types, orbital parameters and solar irradiance, and aerosols), and described in more detail by Gent et al. (2011) . Output from the

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Peter J. Lawrence, Johannes J. Feddema, Gordon B. Bonan, Gerald A. Meehl, Brian C. O’Neill, Keith W. Oleson, Samuel Levis, David M. Lawrence, Erik Kluzek, Keith Lindsay, and Peter E. Thornton

–2100 projected transient climate experiments; and 4) investigates the historical biogeophysical impacts of land use and land cover change in the absence of and in combination with other climate forcing, such as increased atmospheric CO 2 , increased deposition of airborne sources of nitrogen, increased aerosols, and other sources of transient climate change. 2. Data and methods a. CMIP5 specified annual land cover change and wood harvest The CMIP5 experimental design protocol specifies transient land cover

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