Martin Možný

Cereal harvest dates in the Czech Republic between 1501 and 2008 as a proxy for March–June temperature reconstruction

Cereal crop harvests reflect the weather patterns of the period immediately preceding them, and thus the dates at which they begin may be used as a source of proxy data on regional climate. Using systematic phenological observations in the Czech Lands (now known as the Czech Republic) after 1845, together with exploration of further surviving documentary evidence (chronicles, diaries, financial accounts etc.), it has proved possible to create series of winter wheat harvest dates for the period 1501–2008. Employing linear regression, the harvesting dates of the main cereal species (wheat, rye, barley, oats) were first converted to winter wheat harvest days and then normalised to the same altitude above sea level. The next step consisted of using series of winter wheat harvest dates to reconstruct mean March–June temperatures in the Czech Republic, applying standard palaeoclimatological methods. Series reconstructed by linear regression explain 70% of temperature variability. A profound cold period corresponding with late winter wheat harvests was noted between 1659 and 1705. In contrast, warm periods (i.e. early winter wheat harvests) were found for the periods of 1517–1542, 1788–1834 and 1946–2008. The period after 1951 is the warmest of all throughout the entire 1501–2008 period. Comparisons with other European temperature reconstructions derived from documentary sources (including grape harvest dates), tree-rings and instrumental data reveal generally close agreement, with significant correlations. Lower correlations around A.D. 1650 and 1750 may be partly related to deterioration of socio-economic conditions in the Czech Lands resulting from prolonged wars. The results obtained demonstrate that it is possible to use widely-available cereal harvest data for climate analysis and also that such data constitute an independent proxy data series for the region of Central Europe crucial to further studies of the potential impact of climatic variability and climate change on agriculture.

Consequences of climate change for the soil climate in Central Europe and the central plains of the United States

This study aims to evaluate soil climate quantitatively under present and projected climatic conditions across Central Europe (12.1°–18.9° E and 46.8°–51.1° N) and the U.S. Central Plains (90°–104° W and 37°–49° N), with a special focus on soil temperature, hydric regime, drought risk and potential productivity (assessed as a period suitable for crop growth). The analysis was completed for the baselines (1961–1990 for Europe and 1985–2005 for the U.S.) and time horizons of 2025, 2050 and 2100 based on the outputs of three global circulation models using two levels of climate sensitivity. The results indicate that the soil climate (soil temperature and hydric soil regimes) will change dramatically in both regions, with significant consequences for soil genesis. However, the predicted changes of the pathways are very uncertain because of the range of future climate systems predicted by climate models. Nevertheless, our findings suggest that the risk of unfavourable dry years will increase, resulting in greater risk of soil erosion and lower productivity. The projected increase in the variability of dry and wet events combined with the uncertainty (particularly in the U.S.) poses a challenge for selecting the most appropriate adaptation strategies and for setting adequate policies. The results also suggest that the soil resources are likely be under increased pressure from changes in climate.

Multi-scalar Indices of Drought in Intensively Farmed Regions of the Czech Republic

Indices related to specific timescales are useful for monitoring and management of droughts. We compare the multi-scalar standardized precipitation index (SPI) and standardized precipitation-evapotranspiration index (SPEI) across the Czech Republic. The different timescales provided by the two indices can be related to different kinds of drought and their agricultural, hydrological and socio-economic impacts. Short timescales pick out variations of soil water that affect crops; water resources held in reservoirs are related to longer timescales. Data recorded since 1901 were examined to identify differences between the effects of precipitation and evapotranspiration on drought frequency. SPEI and SPI gave different indications during decades with cool dry summers (the first two decades of the twentieth century), the hottest summers (the end of the twentieth century), warm, wet springs (at the beginning of the twentieth century) and years with a big water deficit (1947, 2003, 1994, 1983 and 1933). There was similarity between the two indices for decades with warm, dry springs (1950s, 1990s and 2000s) and very long sunshine hours. The role of temperature is very evident in summer droughts that are driven by temperature anomalies, contributing to a higher potential evapotranspiration at the end of the century.

Climate variability and changes in the agricultural cycle in the Czech Lands from the sixteenth century to the present

This contribution analyses the influence of long-term climate variability on changes in the agricultural cycle in the Czech Lands over the course of the past five centuries. Series of crop- and grape-harvest (for wine) dates were compiled from rich documentary evidence for the periods of 1517–1542, 1561–1622, 1770–1815, 1871–1910 and 1971–2010. Two model areas were selected: the Louny region in north-west Bohemia and the Elbe region in central Bohemia. Fluctuations in selected agricultural series are compared with those expressed in temperature, precipitation and Standardised Precipitation Evapotranspiration Index (SPEI) series for various combinations of months. The basic statistics for the agricultural series are presented, and these are correlated with climatic variables. The earliest starts for harvests occurred in the recent 1971–2010 period and the 1517–1542 period. Harvest dates were comparatively delayed in the three remaining periods. Air temperature, also combined with the drought effect as expressed by SPEI, played a significant role in the agricultural cycle in all periods analysed except 1871–1910, in which temperatures were notably dominant as quite wet patterns prevailed. Summer precipitation played a significant role in the first three periods analysed. Correlation coefficients of agricultural series with temperatures indicate increasing weight for this factor over the course of the centuries. Possible effects of uncertainties in agricultural and climatic data in the results obtained are discussed, as well as the relationship of the agricultural cycle to climate variables and its broader context.