Water, not temperature, governs life in West Africa, and the region is both temporally and spatially greatly affected by rainfall variability. Recent rainfall anomalies, for example, have greatly reduced crop productivity in the Sahel area. Rainfall indices from recent centuries show that multidecadal droughts reoccur and, furthermore, that interannual rainfall variations are high in West Africa. Current knowledge of historical rainfall patterns is, however, fairly limited. A detailed rainfall chronology of West Africa is currently only available from the beginning of the 19th century. For the 18th century and earlier, the records are still sporadic, and an interannual rainfall chronology has so far only been obtained for parts of the Guinea Coast. Thus, there is a need to extend the rainfall record to fully understand past precipitation changes in West Africa. The main challenge when investigating historical rainfall variability in West Africa is the scarcity of detailed and continuous data. Readily available meteorological data barely covers the last century, whereas in Europe and the United States for example, the data sometimes extend back two or more centuries. Data availability strongly correlates with the historical development of West Africa. The strong oral traditions that prevailed in the pre-literate societies meant that only some of the region’s history was recorded in writing before the arrival of the Europeans in the 16th century. From the 19th century onwards, there are, therefore, three types of documents available, and they are closely linked to the colonization of West Africa. These are: official records started by the colonial governments continuing to modern day; regular reporting stations started by the colonial powers; and finally, temporary nongovernmental observations of various kinds. For earlier periods, the researcher depends on noninstrumental observations found in letters, reports, or travel journals made by European slave traders, adventurers, and explorers. Spatially, these documents are confined to the coastal areas, as Europeans seldom ventured inland before the mid-1800s. Thus, the inland regions are generally poorly represented. Arabic chronicles from the Sahel provide the only source of information, but as historical documents, they include several spatiotemporal uncertainties. Climate researchers often complement historical data with proxy-data from nature’s own archives. However, the West African environment is restrictive. Reliable proxy-data, such as tree-rings, cannot be exploited effectively. Tropical trees have different growth patterns than trees in temperate regions and do not generate growth rings in the same manner. Sediment cores from Lake Bosumtwi in Ghana have provided, so far, the best centennial overview when it comes to understanding precipitation patterns during recent centuries. These reveal that there have been considerable changes in historical rainfall patterns—West Africa may have been even drier than it is today.
Changes in Precipitation Over West Africa During Recent Centuries
Poland’s Climate in the Last Millennium
The reconstruction of climate in Poland in the past millennium, as measured by several kinds of proxy data, is more complete than that of many other regions in Europe and the world. In fact, the methods of climate reconstruction used here are commonly utilized for other regions. Proxy data available for Poland (whether by documentary, biological, or geothermal evidence) mainly allow for reconstructions of three meteorological variables: air temperature, ground-surface temperature, and precipitation. It must be underlined however, that air temperature reconstructions are possible only for certain times of the year. This is particularly characteristic of biological proxies (e.g., tree rings measure January–April temperature, chironomids provide data for August temperature, chrysophyte cysts identify cold seasons, etc.). Potentially, such limitation has no corresponding documentary evidence. In Poland these data are available only for climate reconstructions covering mainly the last 500 years because the number of historical sources pre-1500 is usually too small. Geothermal data allow for reconstruction of mean annual ground surface temperature generally for the last 500 years. Reconstructions of air temperature that cover the entire, or almost the entire, millennium and have high time resolution are only available from biological proxies (tree rings, chironomids, diatoms, etc.). At present, the best source of information about climate in Poland in the last millennium is still documentary evidence. This evidence defines a Medieval Warm Period (MWP), which was present in the 11th century and probably ended in the 14th or early 15th century. Air temperature in the MWP was probably about 0.5–1.0°C warmer than contemporary conditions on average, and the climate was characterized by the greatest degree of oceanity throughout the entire millennium. A Little Ice Age (LIA) can be also distinguished in Poland’s climate history. Data show that it clearly began around the mid-16th century and probably ended in the second half of the 19th century. In this LIA, winters were 1.5–3.0°C colder than present conditions, while summers tended to be warmer by about 0.5°C. As a result, the continentality of the climate in the LIA was the greatest for the entire millennium. Mean annual air temperature was probably lower than the modern temperature by about 0.9–1.5°C. The average rise of air temperature since the mid-19th century, which is often called the Contemporary Warming Period (CWP), is equal to about 1°C and is in line with the results of reconstructions using geothermal and dendrochronological methods. The reconstruction of precipitation in Poland is much more uncertain than the reconstruction of air temperature. There was probably considerably higher average precipitation in the 12th century (and particularly in the second half of this century), in the first half of the 16th century, and also in the first half of the 18th century. The second half of the 13th century and the first half of the 19th century were drier than average. In other periods, precipitation conditions were close to average, including for the entire CWP period.
The Advent of Climate Science
Deborah R. Coen
The advent of climate science can be defined as the historical emergence of a research program to study climate according to a modern definition of climate. Climate in this sense: (1) refers not simply to the average state of the atmosphere but also to its variability; (2) is multiscalar, concerned with phenomena ranging from the very small and fast to the very large and slow; and (3) is understood to be influenced by the oceans, lithosphere, cryosphere, and biosphere. Most accounts of the history of climate science to date have focused on the development of computerized general circulation models since World War Two. However, following this definition, the advent of climate science occurred well before the computer age. This entry therefore seeks to dispel the image of climate science as a recent invention and as the preserve of an exclusive, North American elite. The historical roots of today’s knowledge of climate change stretch surprisingly far back into the past and clear across the world, though the geographic focus here is on Europe and North America. The modern science of climate emerged out of interactions between learned and vernacular knowledge traditions, and has simultaneously appropriated and undermined traditional and indigenous forms of climate knowledge. Important precedents emerged in the 17th and 18th centuries, and it was in the late 19th century that a modern science of climate coalesced into a coordinated research program in part through the unification of divergent knowledge traditions around standardized techniques of measurement and analysis.
Geological, Paleoclimatological, and Archaeological History of the Baltic Sea Region Since the Last Glaciation
Jan Harff, Hauke Jöns, and Alar Rosentau
The correlation of climate variability; the change environment, in particular the change of coastlines; and the development of human societies during the last millennia can be studied exemplarily in the Baltic area. The retreat of the Scandinavian ice-sheet vertical crustal movement (glacio-isostatic adjustment), together with climatically controlled sea-level rise and a continuously warming atmosphere, determine a dramatic competition between different forcings of the environment that advancing humans are occupying step by step after the glaciation. These spatially and temporally changing life conditions require a stepwise adjustment of survival strategies. Changes in the natural environment can be reconstructed from sedimentary, biological proxy data and archaeological information. According to these reconstructions, the main shift in the Baltic area’s environment happened about 8,500 years before present (BP) when the Baltic Sea became permanently connected to the Atlantic Ocean via the Danish straits and the Sound, and changed the environment from lacustrine to brackish-marine conditions. Human reaction to environmental changes in prehistoric times is mainly reconstructed from remains of ancient settlements—onshore in the uplifting North and underwater in the South dominated by sea-level rise. According to the available data, the human response to environmental change was mainly passive before the successful establishment of agriculture. But it became increasingly active after people settled down and the socioeconomic system changed from hunter-gatherer to farming communities. This change, mainly triggered by the climatic change from the Holocene cool phase to the warming period, is clearly visible in Baltic basin sediment cores as a regime shift 6,000 years (BP). But the archaeological findings prove that the relatively abrupt environmental shift is reflected in the socioeconomic system by a period of transition when hunter-gatherer and farming societies lived in parallel for several centuries. After the Holocene warming, the permanent regression in the Northern Baltic Sea and the transgression in the South did affect the socioeconomic response of the Baltic coastal societies, who migrated downslope at the regressive coast and upslope at the transgressive coast. The following cooling phases, in particular the Late Antique Little Ice Age (LALIA) and the Little Ice Age (LIA), are directly connected with migration and severe changes of the socioeconomic system. After millennia of passive reaction to climate and environmental changes, the Industrial Revolution finally enabled humans to influence and protect actively the environment, and in particular the Baltic Sea shore, by coastal constructions. On the other hand, this ability also affected climate and environment negatively because of the disturbance of the natural balance between climate, geosystem, and ecosystem.
Viennese School of Climatology
Vienna was a metropolis in the middle of the Danube monarchy of Austria-Hungary and under the rule (1848–1916) of Emperor Franz Joseph I (1830–1916) the city experienced rapid growth and an unprecedented flowering of culture, the arts, architecture and science. The capital of the monarchy, an intellectual melting pot, was a city of distinguished personalities who formed the Second Viennese School of music, the Austrian School of economic thought and many more doctrines, including the ideas of Sigmund Freud, the founder of psychoanalysis. Vienna clearly reflected the zeitgeist of the fin de siècle in its economic, scientific, and cultural heyday. At the end of the 19th century, meteorology and climatology became recognized scientific disciplines, and dynamical meteorology developed during the first quarter of the 20th century. The fact that imperial Austria took a leading position in these developments mostly owes to the work of renowned scientists of the Central Institute for Meteorology and Geodynamics (Zentralanstalt für Meteorologie und Geodynamik, ZAMG) in Vienna. The institute was founded in 1851, and the astronomer Karl Kreil (1798–1862) became the first director. One of Kreil’s goals was to ensure that both the central meteorological station and the growing number of new meteorological stations across the entire territory of the Austrian Empire were equipped with all the appropriate instruments. Another important goal was the processing of the existing observations to publish in the institute’s yearbooks. In truth, that was the starting signal for all further scientific developments, including that of the Viennese School of Climatology. During the first decade of the 1900s, Julius Hann (1839–1921), the third director of the ZAMG, was already being acknowledged as a renowned meteorologist and climatologist. He was a pioneer in gathering and synthesizing global climatological and meteorological data, and his Handbook of Climatology (Handbuch der Klimatologie; Hann, 1883 [Hann, J. (1883). Handbuch der Klimatologie. Stuttgart, Germany: J. Engelhorn]) and Textbook of Meteorology (Hann, 1901 [Hann, J. (1901). Lehrbuch der Meteorologie. Leipzig, Germany: C. H. Tauchnitz]) were standard setters (Davies, 2001 [Davies, H. C. (2001). Vienna and the founding of dynamical meteorology. In C. Hammerl, W. Lenhardt, R. Steinacker, & P. Steinhauser (Eds.), Die Zentralanstalt für Meteorologie und Geodynamik 1851–2001: 150 Jahre Meteorologie und Geophysik in Österreich (pp. 301–312). Graz, Austria: Leykam Buchverlagsgesellschaft]). In Hann’s era, one began to speak of a “Viennese or Austrian school.” Heinrich Ficker, who later became director of the institute, defined its distinguishing characteristic as a school that did not simply adhere to one direction but promoted each direction, every peculiar talent, and the ideas that a meteorologist with necessary characteristics was always present at key turning points in meteorological research.
Meteorology in Vietnam, Pre-1850
The emergence of meteorology in Vietnam did not begin in 1898–1899, with the French installation of a central meteorological observatory in Phù Liễn, near Hải Phòng, and a network of meteorological stations across Indochina. Prior to the colonial time, the ethnic Vietnamese, as well as other ethnic groups such as the Cham, Muong, and Tay-Thai, developed their own knowledge of meteorological phenomena that functioned within their farming practices and cultural frameworks. While further research concerning traditional meteorological knowledge of minority groups in Vietnam is needed, substantial evidence allows a preliminary survey on the practices of the ethnic Vietnamese. Between 1000 and the 1850s, the Vietnamese expanded outwards from their original homeland in the lowlands of north and north-central Vietnam. They adopted the written language, thought systems, and technologies of imperial China, which predisposed them to an enduring Chinese-style meteorological ideology. The Vietnamese viewed weather extremes and other natural anomalies not merely as natural processes. Because meteorological phenomena were “Heaven-sent” warnings of cosmological disasters, Vietnamese dynastic rulers, as well as local farmers and rice producers, interpreted these signs as a demand for moral change. Redressing the authorities’ governance, according to their view, helped rehabilitate the equilibrium of the cosmos. Hence, the records of weather events in Vietnamese historical documents do not simply describe the conditions of past weather, but more importantly, the situations in which the cosmos was no longer in balance. One need not assume that premodern meteorology lacked material grounds. In Vietnam, meteorological knowledge and practices were strongly associated with wet rice cultivation. Vietnamese authorities maintained official agencies to produce yearly calendars that traced proper timing for rice crops, while the populace accumulated experience-based knowledge about seasonal rainfall. Intellectuals, too, expanded their interests to include meteorological knowledge because the subject enriched their philosophy of nature, as in the case of Confucian thinker Lê Quý Đôn (1726–1784), or their medical practices, as in the case of physician Lê Hữu Trác (1720–1791). The advances of Southeast Asian paleoclimate reconstruction since the beginning of the 21st century have added new ideas and methodologies to the study of premodern meteorology in Vietnam. A stronger partnership between climate scientists and historians will therefore facilitate more sophisticated investigations into the knowledge and practices that the Vietnamese developed to respond to weather and climate dynamics.