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T. M. L. Wigley, S. J. Smith, and M. J. Prather

effect by influencing the abundances of various greenhouse gases. We consider here their effects on methane (CH 4 ), tropospheric ozone (O 3 ) and a range of hydrogenated halocarbons such as hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) ( Shine et al. 1990 ; Johnson and Derwent 1996 ; Fuglestvedt et al. 1996 ), gases that do have direct radiative forcing effects. We do not consider their possible effects on aerosols, whose abundances could be affected by reactive gas

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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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Martin P. Hoerling and Arun Kumar

1999 for 500-hPa heights. The question remains open whether this linear signal constitutes the sole tropically forced teleconnection, or whether there exist additional response patterns to so-called different flavors of tropical SST forcing associated with individual ENSO events, or to some other non-ENSO SST forcing. Understanding the atmospheric response to tropical forcing beyond the linear ENSO signal is an outstanding problem in clarifying the sources and predictability of climate variations

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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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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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Niklas Schneider and Bruce D. Cornuelle

al. 1997 ); North American precipitation, streamflow, and surface temperature anomalies ( Mantua and Hare 2002 ; Dettinger et al. 1998 ; Cayan et al. 1998 ); surface temperature anomalies in northeastern Asia ( Minobe 2000 ); fluctuations of the Asian monsoon ( Krishnan and Sugi 2003 ); and a modulation of El Niño–Southern Oscillation (ENSO) teleconnections ( Gershunov and Barnett 1998 ). This covariation can result from the PDO forcing the atmosphere or from a common forcing of the PDO and

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Hai Lin and Jacques Derome

1. Introduction Numerous studies have been done on the linkage between the anomalous tropical Pacific sea surface temperature (SST) and the interannual variability of the extratropical circulation ( Trenberth et al. 1998 ). The extratropical response to the El Niño forcing is a “Pacific– North American (PNA)” teleconnection pattern ( Wallace and Gutzler 1981 ). This signal accounts for a significant part of the variance of interannual variability in the midlatitude North Pacific and North

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Gabriel Chiodo and Lorenzo M. Polvani

1. Introduction Stratospheric ozone, and its response to anthropogenic forcings, provide an important pathway for the coupling between atmospheric composition and climate ( Isaksen et al. 2009 ). Quantifying the impact of that ozone response on tropospheric and surface climate is a key step toward assessing the importance of an interactive stratospheric ozone chemistry in climate change projections and, more generally, on the role of the ozone layer in the climate system. It has recently been

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Gerald A. Meehl, Warren M. Washington, Caspar M. Ammann, Julie M. Arblaster, T. M. L. Wigley, and Claudia Tebaldi

1. Introduction Previous studies with global coupled models have shown that a specification of the major known forcings that acted on the climate system in the twentieth century [e.g., such as greenhouse gases (GHGs), solar, volcanoes, etc.] can reproduce, to first order, many aspects of the observed time series of globally averaged temperature for that time period ( Stott et al. 2000 ; Meehl et al. 2003 ; Ammann et al. 2003 ; Broccoli et al. 2003 ). It has been assumed in a number of these

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Robert E. Dickinson

1086 JOURNAL OF CLIMATE VOLUME IThe Force-Restore Model for Surface Temperatures and Its Generalizations ROBERT E. DICKINSONNational Center for Atmospheric Research,* Boulder, Colorado(Manuscript received 29 January 1988, in final form 23 June 1988) Atmospheric general circulation models require efficient approximation procedures for including the verticaldiffusion of

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