Marcel Küttel

Chapter 1 Mediterranean climate variability over the last centuries: A review

Publisher Summary This chapter discusses a necessary task for assessing to which degree the industrial period is unusual against the background of pre-industrial climate variability. It is the reconstruction and interpretation of temporal and spatial patterns of climate in earlier centuries. There are distinct differences in the temporal resolution among the various proxies. Some of the proxy records are annually or even higher resolved and hence record year-by-year patterns of climate in past centuries. Several of the temperature reconstructions reveal that the late twentieth century warmth is unprecedented at hemispheric scales and is explained by anthropogenic, greenhouse gas (GHG) forcing. The chapter discusses the availability and potential of long, homogenized instrumental data, documentary, and natural proxies to reconstruct aspects of past climate at local- to regional-scales within the larger Mediterranean area, which includes climate extremes and the incidence of natural disasters. The chapter describes the role of external forcing, including natural and anthropogenic influences, and natural, internal variability in the coupled ocean–atmosphere system at subcontinental scale.

Climate Change in Poland in the Past Centuries and its Relationship to European Climate: Evidence from Reconstructions and Coupled Climate Models

We investigate the winter temperature and precipitation evolution over Poland over the last half millennium in comparison with the European average in reconstructions/instrumental data and in the ECHO-G and HadCM3 models and discuss the physical processes behind those variations. Results indicate very good agreement between European land and Polish winter temperatures in reconstructions and in the models. Colder winter conditions were found within the ‘Little Ice Age’ and temperatures at the turn of the twenty first century are very likely the warmest in the context of the past. The strong agreement between Polish winter temperature and European mean conditions is of major interest since some of the longest European proxy information stem from Poland and therefore can improve European temperature reconstructions significantly. Precipitation results indicate that reconstructions over Poland agree well with those of the rest of Europe, though the agreement is poorer between the reconstruction and the models. The role of the large-scale atmospheric circulation dynamics/forcing connected with the observed Polish winter temperature/precipitation changes is investigated in the reconstructions and in the model world. The most important atmospheric circulation pattern for winter temperature variability is the North Atlantic Oscillation (NAO). The Scandinavian (SCAND) and to a lesser degree also the NAO and East Atlantic/Western Russia (EA/WRUS) are of relevance for winter precipitation variations in Poland. Canonical Correlation Analysis (CCA) results show that the leading circulation modes responsible for dry/wet and warm/cold Polish winter conditions are in good agreement in the reconstructions and models. These results suggest that the models are able to reproduce the links in instrumental and proxy data and also that the large- to regional-scale relationships are robust during the last centuries. The stability of the large- to regional-scale links is relevant for downscaling approaches and also for palaeoclimate reconstructions.