Climate of the Past www.clim-past.net 1814-9324 1814-9332 8 1 2012 10.5194/cp-8-25-2012 http://www.clim-past.net/8/25/2012/ http://www.clim-past.net/8/25/2012/cp-8-25-2012.html http://www.clim-past.net/8/25/2012/cp-8-25-2012.pdf 25 36 2012-01-04 Internal and external variability in regional simulations of the Iberian Peninsula climate over the last millennium J. J. Gómez-Navarro J. P. Montávez montavez@um.es P. Jiménez-Guerrero S. Jerez R. Lorente-Plazas J. F. González-Rouco E. Zorita Departamento de Física, Universidad de Murcia, Spain Departamento de Astrofísica y CC. de la Atmósfera, Universidad Complutense de Madrid, Madrid, Spain Helmholtz-Zentrum Geesthacht, Geesthacht, Germany In this study we analyse the role of internal variability in regional climate simulations through a comparison of two regional paleoclimate simulations for the last millennium. They share the same external forcings and model configuration, differing only in the initial condition used to run the driving global model simulation. A comparison of these simulations allows us to study the role of internal variability in climate models at regional scales, and how it affects the long-term evolution of climate variables such as temperature and precipitation. The results indicate that, although temperature is homogeneously sensitive to the effect of external forcings, the evolution of precipitation is more strongly governed by random unpredictable internal dynamics. There are, however, some areas where the role of internal variability is lower than expected, allowing precipitation to respond to the external forcings. In this respect, we explore the underlying physical mechanisms responsible for it. 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