INTERNATIONAL JOURNAL OF CLIMATOLOGY Int. J. Climatol. 24: 1759–1776 (2004) Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/joc.1106 CLASSIFICATION AND ANALYSIS OF PAST CLIMATE INFORMATION BASED ON HISTORICAL DOCUMENTARY SOURCES FOR THE CARPATHIAN BASIN JUDIT BARTHOLY, a, * RITA PONGR ´ ACZ a and ZS ´ OFIA MOLN ´ AR b a Department of Meteorology, E¨ otv¨ os Lor´ and University, Budapest, Hungary b Regional Center of Northern Hungary, Hungarian Meteorological Service, Miskolc, Hungary Received 4 February 2003 Revised 17 January 2004 Accepted 23 February 2004 ABSTRACT In order to cover a millennium-long period in climatological studies, several types of information must be taken into consideration. Beyond the regular meteorological observations, historical documentary data may serve as a basic source for the past centuries. For the Carpathian basin, R´ ethly collected historical documents containing meteorology-related information. In order to facilitate the analysis of this documentary collection, a special code system using hierarchical subclasses has been defined and applied to approximately 15 000 collected climatological items. The spatial and temporal distributions of temperature- and precipitation-related climate events and extremes have been evaluated using settlement and subregional scales. Also, the geographical distribution of extreme climatological events has been mapped. Annual and seasonal time series have been analysed for the Carpathian basin and compared with other reconstructed temperature and precipitation index time series from other geographical locations outside the Carpathian basin. Copyright  2004 Royal Meteorological Society. KEY WORDS: historical documentary sources; proxy climate data; R´ ethly’s collection; temperature; precipitation; Carpathian basin; time series reconstruction; extreme events 1. INTRODUCTION Extreme meteorological events significantly affect various types of human activity, e.g. agriculture, energy consumption, industry and transportation. The growing human population of planet Earth relies on its natural resources; therefore, any disturbance of the current equilibrium of the natural systems may result in severe consequences for human societies. According to the IPCC Third Assessment Report (Houghton et al., 2001), regional impacts of global climate change tend to intensify extremes and contribute to the more frequent occurrence of extreme climatological events. In order to provide regional climate scenarios for any particular area, past climate tendencies and climatological extremes must be analysed. Since regular reliable observations cover only one or two centuries, other historical information from documentary sources must be taken into consideration, as well as meteorological measurements. This paper focuses on the documentary collection of R´ ethly (Bartholy et al., 2001) and analyses the climatological information provided by these sources; a different methodology was applied to the R´ ethly collection by Racz (1999). For the 20th century, regular meteorological measurements in the Carpathian basin are available in order to analyse centennial tendencies, extremes and changes of temperature and precipitation (Mika et al., 2001). Based on homogenized (Szentimrey, 1999) datasets, Figure 1 summarizes the structure of the annual distribution of monthly temperature and precipitation anomalies in the Carpathian basin for the last 100 years. * Correspondence to: Judit Bartholy, Department of Meteorology, E¨ otv¨ os Lor´ and University, Pf. 32., H-1518, Budapest, Hungary; e-mail: bari@ludens.elte.hu Copyright  2004 Royal Meteorological Society