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Timothy Andrews

1. Introduction Radiative forcings have long been used to quantify and rank the drivers of climate change (e.g., Hansen et al. 1997 ; Shine and Forster 1999 ). In climate models, radiative forcings can help us understand why different models differ in their simulations of the past and future. For example, Forster et al. (2013) found the intermodel spread in the global surface temperature change across phase 5 of the Coupled Model Intercomparison Project (CMIP5) ( Taylor et al. 2012

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Amy H. Butler, David W. J. Thompson, and Ross Heikes

1. Introduction There is increasing evidence that anthropogenic forcing has driven and will drive several robust changes in the extratropical circulation. Among the most robust changes are poleward shifts in the extratropical storm tracks consistent with positive trends in the northern and southern annular modes of variability. Observations reveal robust positive trends in the southern annular mode (SAM) during austral spring/summer that are consistent with forcing by the Antarctic ozone hole

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Hiroki Ichikawa, Hirohiko Masunaga, Yoko Tsushima, and Hiroshi Kanzawa

1. Introduction The radiative effect of clouds, often called cloud radiative forcing (CRF), associated with convective activity largely controls the radiative balance–imbalance at the top of the atmosphere (TOA) over the tropics through the horizontal extension of high clouds that accompany deep convection ( Ramanathan and Collins 1991 ; Lindzen et al. 2001 ; Hartmann et al. 2001 ). The response of CRF associated with convective activity to an imposed climate perturbation is thus fundamental

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Michael P. Meredith, Alberto C. Naveira Garabato, Andrew McC. Hogg, and Riccardo Farneti

help to evaluate changes in the overturning. In this paper, we investigate an ocean at (or close to) the eddy-saturated limit, and evaluate how the overturning circulation will behave at this limit. The overall response of the overturning circulation in the Southern Ocean to changes in wind stress forcing will depend on the differing responses of the Eulerian mean and eddy-induced components ( Fig. 1 ). The magnitude of the Eulerian mean overturning is reasonably expected to be linear with wind

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Jiapeng Miao, Tao Wang, Huijun Wang, Yali Zhu, and Jianqi Sun

. This is partly caused by suppressed ENSO-associated tropical Indo–western Pacific sea surface temperature (SST) variability, reduced EAWM interannual variability, and northward-retreating EAWM signals. The EAWM intensity is also regulated by the Arctic Oscillation (AO) on the interannual time scale ( Gong et al. 2001 ; Wu and Wang 2002 ). Furthermore, the Arctic amplification and sea ice loss may affect the EAWM ( Wang and Liu 2016 ; Zhou 2017 ). Both anthropogenic forcings [e.g., greenhouse

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Haijun Yang and Lu Wang

the tropical ocean also tend to be shallow and symmetric to the equator under the symmetric extratropical forcing. Quantitative assessment of the extratropical impact on the tropical Atlantic has yet to be clarified. There are lots of observational and modeling studies on how the climate changes in the northern North Atlantic affect the tropical Atlantic ( Curry et al. 1998 ; Zhang and Delworth 2006 ; Sutton and Hodson 2007 ; Chang et al. 2008 ; Zhang et al. 2011 ). The thermal or freshwater

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Barbara Winter and Michel S. Bourqui

forcing in the polar vortex and thus an increased Brewer–Dobson circulation, with associated reduced vortex strength and higher temperatures in the polar lower stratosphere ( Rind et al. 1998 ; Sigmond et al. 2004 ; Braesicke and Pyle 2004 ; Butchart et al. 2006 ; Olsen et al. 2007 ; Winter and Bourqui 2010 ). The question has then been asked whether the stratosphere in such experiments is responding to the radiative effect of the increased greenhouse gas loading throughout the atmosphere or to

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Qigang Wu

dependent on lag and seasons. When SST leads Z500, about 80%–85% of the TSC is explained by the first MCA mode. The coupled patterns associated with the first MCA mode when SST and Z500 is assigned at DJF and JFM (not shown) indicate the forcing of atmosphere in the extratropics by the SST associated with conventional ENSO events in the tropical Pacific. The ENSO signature of extratropical atmospheric variability is very similar to that in the SVD analyses conducted between the seasonal mean Z500 and

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Tim Woollings, Abdel Hannachi, Brian Hoskins, and Andrew Turner

the mean flow forcing of transient eddies. As described by Ambaum et al. (2001) , it is clearly separated from the subtropical jet that is developing over the subtropical North Atlantic. On negative NAO days, in contrast, the two jet streams have merged to form one broad, continuous jet across the Atlantic. Several studies have suggested that these jet stream variations arise as a result of mean flow forcing associated with the breaking of transient, synoptic-scale Rossby waves (e.g., Benedict

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Ryan J. Kramer, Brian J. Soden, and Angeline G. Pendergrass

the surface radiative changes across models have received less attention. The forcing-feedback framework for understanding top-of-atmosphere (TOA) radiative changes (e.g., Sherwood et al. 2015 ) can also be applied to radiative changes at the surface ( Andrews et al. 2009 ; Colman 2015 ). A change in a forcing agent, such as CO 2 concentration, causes an instantaneous radiative perturbation at the surface, herein referred to as an instantaneous surface radiative forcing (ISRF). Rapid radiative

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