INTERNATIONAL JOURNAL OF CLIMATOLOGY Int. J. Climatol. (2012) Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/joc.3580 Assessment of climate change in Europe from an ensemble of regional climate models by the use of K¨ oppen–Trewartha classification Clemente Gallardo, a * Victoria Gil, b Edit Hagel, b C´ esar Tejeda b and Manuel de Castro a,b a Instituto de Ciencias Ambientales, Universidad de Castilla-La Mancha, Toledo, Spain b Instituto Meteorol´ ogico Regional de Castilla-La Mancha, Toledo, Spain ABSTRACT: Through the use of the climatic classification of K¨ oppen–Trewartha (K-T), the ability to reproduce the current climate of Europe has been shown for an ensemble of 15 regional climate model simulations nested in six global climate models. Depending on the simulation, between 55.4 and 81.3% of the grid points are in agreement with observations regarding the location of climate types in current climate simulations (1971 – 2000). In this respect, the result of the ensemble of 15 simulations is better than that of any individual model, with 83.5% of the grid points in agreement with observations. K-T classification has also been used to analyse the projected climate change over the 21 st century under the SRES-A1B emissions scenario. It was found that 22.3% of the grid points in the domain change their climate by the period 2021–2050 compared to current climate and 48.1% change by 2061–2090. The climate shifts affecting the biggest extensions are projected in Central Europe and Fennoscandia, but other smaller areas suffer more intense changes which potentially are more dangerous to vegetation and ecosystems. Generally, these changes occur at a sustained rate throughout the century, reaching speeds of up to 90 × 10 3 km 2 decade −1 in the retreat or expansion of some climates. Copyright  2012 Royal Meteorological Society KEY WORDS climate classification; climate change; regional climate models; ensemble Received 21 February 2012; Revised 15 July 2012; Accepted 30 July 2012 1. Introduction A climate-vegetation scheme, like the K¨ oppen climate classification (K¨ oppen, 1936) or its improvements (Tre- wartha and Horn, 1980) is a complex system of climates, which is based on the two variables most frequently used in climate studies: precipitation and temperature. The categories or types of these classifications are not only related to the different climates that exist on the Earth, but they are structurally related to the potential vegetation of each zone, and are also indirectly related to the feasible crops and ecosystems. These relationships allow us not only to establish a projection of the future changes in the climate, but also to give a basic estimation of the possible effects on the natural vegetation, crops and ecosystems. AK¨ oppen-like climate classification has two additional advantages. First, it can be applied practically everywhere on the planet, as the temperature and precipitation data are available almost anywhere over the globe. Second, these variables are also part of the standard output of global climate models (GCMs) and regional climate models (RCMs). Owing to these properties, the K¨ oppen methodology can be applied to track past and future ∗ Correspondence to: C. Gallardo, Instituto de Ciencias Ambientales, Universidad de Castilla-La Mancha, Avda. Carlos III s/n, 45071 Toledo, Spain. E-mail: clemente.gallardo@uclm.es changes in the climate, using the observations that have been gathered over the last 100 years or so, and the outputs of the climate models for past, present or future periods. Within the field of the study of climate change, the K¨ oppen climate classification and its variants have been used by several authors. Lohmann et al. (1993) used the K¨ oppen classification to check whether a GCM was able to reproduce the present day climate and to analyse how the main climate regions could change as a result of global warming. Leemans et al. (1996) analysed the global biome distribution by applying the K¨ oppen method to the output of four GCMs. Kleidon et al. (2000) estimated the effect of vegetation on the global climate by performing several climate model simulations and then applying the K¨ oppen classification to illustrate the differences among them. Jylh¨ a et al. (2010) used the traditional K¨ oppen classification to study climate trends in Europe with a set of 19 GCMs. Feng et al. (2012) assessed current and future climate changes in the Arctic from the output of 16 GCMs. The K¨ oppen classification has also been applied to the output of RCMs in order to evaluate climatic refuge for the People’s Republic of China (Baker et al., 2010), assess the possible increase of aridity caused by the late 21 st century climate change in the Mediterranean region (Gao and Giorgi, 2008), quantify the potential impact of climate change on ecosystems of the Barents Sea Region Copyright  2012 Royal Meteorological Society