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G. Chiodo, L. M. Polvani, D. R. Marsh, A. Stenke, W. Ball, E. Rozanov, S. Muthers, and K. Tsigaridis

1. Introduction An accurate quantification of the effects of anthropogenic emissions on the ozone layer is a key step toward making accurate predictions of the future ozone evolution. Assessing the ozone response to anthropogenic forcings is also a step toward improved understanding of the coupling between atmospheric composition and climate ( Isaksen et al. 2009 ). There is robust modeling evidence suggesting that anthropogenic greenhouse gases (GHGs), via their influences on stratospheric

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Jessica M. Loriaux, Geert Lenderink, and A. Pier Siebesma

a reference, we systematically vary the relative humidity, stability, and large-scale vertical velocity. Furthermore, this analysis is repeated under a temperature perturbation, to simulate a warmer climate. Within a convective framework, based on a case study of Loriaux et al. (2016b) , we thus aim to understand how precipitation depends on atmospheric conditions and lateral forcing, and analyze how precipitation is affected by a climate perturbation. To this end, we first present our methods

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Martin Rypdal and Kristoffer Rypdal

1. Introduction When the climate system is subject to radiative forcing, the planet is brought out of radiative balance and the thermal inertia of the planet makes the surface temperature lag behind the forcing. The time constant τ , which is the time for relaxation to a new equilibrium after a sudden change in forcing, has been considered to be an important parameter to determine. The equilibrium climate sensitivity S eq , the temperature rise per unit forcing after relaxation is complete

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Chen Xing, Fei Liu, Bin Wang, Deliang Chen, Jian Liu, and Bin Liu

1. Introduction Large volcanic eruptions provide an important external forcing that has caused significant global surface cooling typically lasting for 3 years ( Crowley 2000 ; Hegerl et al. 2003 ; Mann et al. 1998 ; Robock 2000 ; Sear et al. 1987 ; Timmreck 2012 ). This cooling process starts when a large amount of SO 2 gas injected into the stratosphere reacts with OH and H 2 O to form sulfate aerosols, which can perturb the radiative balance ( Robock 2000 ). For example, the year after

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Ge Shi, Wenju Cai, Tim Cowan, Joachim Ribbe, Leon Rotstayn, and Martin Dix

aerosols seems to be supported by the fact that transient climate model simulations forced only by increased greenhouse gases, without the inclusion of aerosol forcing, have generally not reproduced the observed rainfall increase over northwestern and central Australia. Whetton et al. (1996) compared rainfall changes in five enhanced greenhouse climate simulations that used coupled GCMs with five that used atmospheric GCMs with mixed layer ocean models. The coupled experiments mostly gave a decrease

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Andrew P. Schurer, Gabriele C. Hegerl, Michael E. Mann, Simon F. B. Tett, and Steven J. Phipps

1. Introduction Climate variability originates from two fundamentally different mechanisms: (i) changes in the large-scale (often global) energy budget of the planet due to influences external to the climate system and (ii) chaotic interactions within and between climate system components, which generate substantial variability over a broad range of time scales (e.g., Hasselmann 1976 ) and are unrelated to this external forcing. The externally forced component can be subdivided into that due

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David M. Straus and J. Shukla

the midlatitude seasonal mean circulation associated with El Niño–Southern Oscillation (ENSO) related tropical SST anomalies can be understood primarily in terms of a shift in the classic Pacific–North American (PNA) teleconnection pattern of internal variability of Wallace and Gutzler (1981) , or whether such SST anomalies generate a fundamentally distinct forced response pattern. One school of thought has taken the position that ENSO SST forcing can selectively amplify natural forms of internal

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Vijayakumar S. Nair, S. Suresh Babu, K. Krishna Moorthy, and S. S. Prijith

. It is well known that the spatial gradients (zonal and meridional) in warming by the greenhouse gases are small because of their homogeneous spatial distribution, whereas the heterogeneity in atmospheric forcing due to aerosols significantly influences the regional climate via dynamical/thermodynamical feedbacks ( Matsui and Pielke 2006 ). Recently, Ming and Ramaswamy (2011) have shown that spatially heterogeneous aerosol forcing could alter the regional-scale circulation pattern through

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Hideo Shiogama, Seita Emori, Kiyoshi Takahashi, Tatsuya Nagashima, Tomoo Ogura, Toru Nozawa, and Toshihiko Takemura

1. Introduction Great uncertainty persists in future projections of the hydrological cycle response to global warming, which is caused by anthropogenic emissions of greenhouse gases and aerosols ( Meehl et al. 2007 ). One of the major sources of uncertainty is the large range of potential climate sensitivities of surface air temperature to radiative forcing ( Gregory et al. 2002 ; Forest et al. 2002 , 2006 ; Knutti et al. 2003 ; Murphy et al. 2004 ; Stainforth et al. 2005 ; Meehl et al

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Gerald A. Meehl, Julie M. Arblaster, and William D. Collins

combinations of natural and anthropogenic forcings, as well as globally and seasonally varying distributions of both reflecting and absorbing BC aerosols scaled in time over the twentieth century by global human population increase ( Meehl et al. 2006a ). In previous experiments with another model [the Parallel Climate Model (PCM)], Meehl et al. (2004) documented climate system responses to the individual anthropogenic (GHGs, the direct effect of sulfate aerosols, ozone) and natural (volcanoes, solar

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