Changes in monetary circulation on urban sites in selected regions of the Byzantine empire (AD 850 e 1300). The diagram presents regional averages of nor- malised frequencies of coin fi nds per year divided into periods determined by regnal years in excavations from each region. Southern Greece: Athens and Corinth (Morrisson, 1991); Western Anatolia: Aphrodisias, Ephesus, Pergamum and Priene (Morrisson, 1991, 2002: Fig. 6.1); Eastern Bulgaria: Preslav and Tyrnovo (Morrisson, 2002: Figs. 6.12 and 6.13); Western Bulgaria: Pernik (Morrisson, 2002: Fig. 6.11). Values were transposed into positive numbers by subtracting the minimal average value in each region from the average values of all periods (the earliest period, AD 811 e 886, was characterised by the minimal value).

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The Medieval Climate Anomaly and Byzantium: A review of the evidence on climatic fluctuations, economic performance and societal change

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At the beginning of the Medieval Climate Anomaly, in the ninth and tenth century, the medieval eastern Roman empire, more usually known as Byzantium, was recovering from its early medieval crisis and experiencing favourable climatic conditions for the agricultural and demographic growth. Although in the Balkans and Anatolia such favourable climate...

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... This growing trend is no longer visible in the eleventh century, and towards the end of the twelfth century the average olive pollen values started to decline rapidly. These changes in the regional olive pollen record from the northern Aegean show interesting correlations with two climate proxies. First, the northern Aegean SSTs reconstruction shows a declining trend after AD 1000 ( Fig. 9), potentially indicating that temperatures were becoming cooler over this part of Greece, which would limit the natural potential for olive cultivation in this area. Moreover, the dendro-based reconstructions of May e June precipitation for the northern Aegean also show a declining trend, this time dated to the twelfth century (Fig. 9). As the late spring rains are crucial for olive harvests, this factor might have additionally worked against olive cultivation in Macedonia and northern Greece in general. In addition, since e as already indicated e the AD 1180s and AD 1190s were a period of relative political instability, with warfare in the Balkans and internal political tensions and con fl ict in and around the capital at Constantinople that affected the trade and market for olive oil. In contrast, there appears to be no indication of longer- term decline in cereals (Fig. 5), although of course this does not exclude some short-term fl uctuations in grain harvests, fl uctuations that would not, of course, be re fl ected in the pollen data. Whereas it is quite probable that the harvests in the years AD 1180 e 1200 were in general lower as a result of adverse climatic conditions, there is more certainty with respect to the poor olive harvests thanks to the observed longer-term decrease in olive pollen in Macedonia. All these factors likely ampli fi ed any instability within the Byzantine socio-political system during the last part of the twelfth century, even though positive demographic trends generally remained unaffected (Figs. 4 and 5). Interestingly, the relatively stable May e June precipitation patterns after AD 1230 (Fig. 9) do not seem to have helped to reverse the overall declining trend in olive cultivation in northern Greece (Fig. 17). All three model simulations show a signi fi cant reduction in winter temperatures around the middle of the thirteenth century related to the great Samalas volcanic eruption (Fig. 16, Sigl et al., 2015; Stoffel et al., 2015) and other tropical volcanic eruptions of that period. Severe winters can damage both vineyards and olive cultivation, since as noted already both of these plants are sensitive to prolonged frost and very low temperatures during winter. Unfortunately, there are no data on olive or vine cultivation or the trade in wine or olive oil during the thirteenth century to help trace the immediate impact of these severe winters on the regional economy. However, it is interesting to observe that the period of severe winters temporally coincides with the fi nal collapse of Byzantine political control over the valleys of western Anatolia (Thonemann, 2011, pp. 270 e 278; cf. Fei et al., 2007, for another case of the impact of a volcanic eruption on medieval political history). At that time, these valleys were inhabited by settled agriculturalists whose identity was mostly Byzantine, and nomad pastoralists, who were predominantly Turkoman. In the course of the second half of the thirteenth century, the Byzantine authorities from Nicaea and then Constantinople gradually lost military and political control over these complex local communities, as they were absorbed into the Turkoman beyliks of western Anatolia (Laiou, 1972, pp. 21 e 30). Possibly that section of the population whose economic activities were centred on cereal, vine, vegetable and olive cultivation, was weakened by the severe winters, conditions that may have been less damaging for the Turkoman pastoralists. The economic impact of such severe winters would consequently reduce the tax resources available to the local Byzantine authorities, while the imperial government from Nicaea was too busy with the recovery of the control of Constantinople to deal with local problems in western Anatolia (Table 1). For the sixty years after the fall of Constantinople (Table 1), eastern Bulgaria shows a positive trend in monetary exchange (Fig. 2) and forms in the thirteenth century the core of the new, fl ourishing Bulgarian empire (Ducellier, 2008). The contraction of monetary circulation is thus observable on sites associated with the Byzantine economic system that started to break down after the fall of Constantinople in AD 1204, and consequent upon the political and economic fragmentation that followed (Laiou and Morrisson, 2007). Although the increased spatial resolution of the climate models used in this review, a detailed view of the evolution of the climate in the eastern Mediterranean cannot yet be achieved. Smaller-scale factors, such as complex coastlines and orography and short time scale sea e land interactions, as well as major processes, such as the connection between the Mediterranean Sea and the North Atlantic, still cannot be realistically represented. The CMIP5/PMIP3 simulations revealed a high degree of internally generated variability. None of the formulated hypotheses can be falsi fi ed concerning i) exact timing and ii) the extent and spatial representation of the model-based results in comparison with the empirical evidence, i.e., natural proxy archives and historical or archaeological evidence. This does not disqualify the ability of both approaches to take into account some general considerations. In- ferences about the true climatic evolution can only be derived from the empirical evidence. Climate models may only represent several possible evolutions of climate under certain con fi gurations in the external background. For instance, the CMIP5/PMIP3 model simulations are carried out with the same protocol using changes in Earth's orbital parameters, solar output and volcanic activity but they all show different evolution on the decadal-to-multi decadal time scale. This analysis of the complex interactions between medieval climate, environment and human activity in Byzantium combined paleaeoclimate records and simulations with textual and archaeological evidences. However, establishing fi rm links between climate change and human activity remains challenging due to the complexity and heterogeneity of available climatic and societal data. The comparative use of palaeomodels in combination with palaeoclimate information and societal evidence signi fi cantly contributes to a better understanding of both the drivers behind the climate system as well as those behind the coupled climate-society system. In this way, we can clarify the links between climate variability and societal impacts and thus study the human capabilities in adjusting to a changing environment. Changes in solar and volcanic activity probably in fl uence climate on annual to decadal time scales. However, during the middle Byzantine period, no prolonged changes in either solar or volcanic activity are evident. It seems most likely, therefore, that changes seen in the model simulations are induced by the internal variability generated by the interactive coupling between the different climatic components. For Byzantium, the ninth and tenth centuries were marked by an agricultural and demographic expansion that was favoured by abundant rainfall and a mild climate. During the following century, while such favourable conditions continued, parts of the empire also experienced external political pressures, such as ...

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... cases of annually-laminated sediments which can be directly compared with speci fi c historical events (e.g., England et al., 2008). This is due to the rather limited number of radiocarbon dates and low sampling resolution in the case of most of the pollen pro fi les from our study area (Luterbacher et al., 2012 and references therein; Izdebski et al., 2015). Hendy (1970, 1989) was the fi rst who suggested that the eleventh e twelfth century constituted a climax in the economic history of Byzantium. Harvey (1989) further demonstrated the increase in the monetisation of the Byzantine economy during the tenth to the twelfth century. This development is also evident in the growing complexity of the monetary system and the new smaller denominations that facilitated the use of money also for everyday transactions and indicate clearly a governmental awareness of the market function of the coinage (Harvey, 1989, p. 89, Hendy, 1970; Morrisson, 1976, 1991, 2002). Harvey (1989) also argued that the changes in the way that tax was collected and the increase in the amount of collected taxes were possible only if the Byzantine economy was expanding (Harvey, 1989, pp. 90 e 102). Moreover, the Byzantine state in the period ca. AD 1000 e ca. 1200 was relatively rich when compared to previous centuries (Morrisson, 1991). Finally, the period from the tenth to the twelfth and possibly even the fourteenth century was characterised by continuous demographic growth in the Byzantine Balkans and Anatolia (Harvey, 1989). Documents also suggest that the total cultivated area on these estates was steadily expanding throughout the tenth to twelfth century (Harvey, 1989, pp. 47 e 58). Harvey's hypotheses regarding the demographic history of Byzantium were supported by Lefort (1985, 1991) and his studies on Macedonia from the tenth to the fourteenth century. The analysis of the frequency of coins per year from securely- dateable archaeological contexts (Metcalf, 1960 and Morrisson, 1991, 2001, 2002) is considered to represent the intensity of monetary circulation that was taking place on a given site. The circulation period of each coin can be assumed to be around two to three decades and is based on the regnal years of the emperor who issued the coin (Morrisson, 1991, pp. 299 e 301). Furthermore, changes in the frequency of coin fi nds per year are one indicator of the degree of expansion and contraction in the local economy, and it is important to note that coin fi nds from archaeological or survey contexts are almost exclusively of the bronze coinage, i.e., the lowest denominations, those used in everyday transactions (Harvey, 1989, pp. 86 e 87). It is, therefore, possible to make temporal connections between on the one hand the expansion and contraction of monetary exchange in a given region based on the incidence of numismatic material from urban sites (Fig. 1), and on the other the political, social and potential climatic impacts. Fig. 2 presents the changes in monetary circulation in different parts of Byzantium. The intensity of monetary exchange increased from the ninth century in southern Greece and western Bulgaria, while a considerable delay is evident for western Anatolia (Fig. 2). A decrease in monetary circulation after AD 1081 is characteristic for almost the entire empire. The second half of the twelfth century is a period of renewed expansion of monetary exchange everywhere across the Byzantine world, whereas a period of substantial contraction starts after AD 1200. At the same time, eastern Bulgaria shows a contrasting positive trend in the thirteenth century (Fig. 2) and it forms the core of the fl ourishing Second Bulgarian empire (Ritter, 2013). A contraction of monetary circulation is observable on sites associated with the Byzantine economic exchange system, which underwent deep fragmentation after AD 1204 (Laiou and Morrisson, 2007, pp. 166 e ...

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... the periods selected in the models do not re fl ect the real climate evolution e and due to the absence of changes in the external forcings a common signal would be a coincidence e the model simulations show a considerable amount of spatial variability, especially for the hydrological changes. Any analysis of socio-economic and political change and transformation for any period of history requires a holistic approach that includes environmental factors, documentary evidence, and the broader geo-political context. In the case of the medieval Byzantine state, it should be clear at the outset that a short study such as this can only collate the key materials and suggest ways forward. We have quite deliberately, therefore, excluded clearly signi fi cant factors such as changing environmental situations among the neigh- bours of the empire, in particular the steppe peoples such as the Pechenegs and Turks, but also in Italy, a major trading partner of the Byzantine empire throughout the period AD 850 e 1300. Climatic shifts in the empire's commercial partners could impact on market demand as well as production, and thus on socio-economic relations within the empire itself (as, for example, in determining estate owners' choices to invest in sericulture, oleoculture or viticulture, major sources of market-derived income). Until the twelfth century Italian cities were major importers of Byzantine grain, for example, so shifts at either end of this relationship could impact negatively as well as positively at the other end. These issues are central to future, more detailed research into the causal associa- tions between climate, environment and society in the Byzantine world, and that what we present here is intended to illustrate both the possibilities as well as the methodologies that can be employed. The middle Byzantine period (ca. AD 800 e ca. AD 1200) generated a considerable body of evidence for the study of climate and society. Natural proxy archives and textual records on past climate, as well as historical, palaeoenvironmental and archaeological data together generate a substantial body of information on speci fi c climate events, variations in weather and climate, societal changes, as well as economic and political fl uctuations (Sections 2 e 4). In particular, the evidence that concerns societal processes is largely multi-factorial in character, while reactions to climate and its variability in respect of both human activities as well as the reactions to climate variability on the part of different sectors of society, both as reported by contemporaries as well as revealed by, for example, archaeological data, have a different spatial and temporal resolution (local, daily to annual) compared with the palaeoclimate records (local to regional, seasonal to multidecadal). Moreover, most of the data relevant to Byzantine society do not build continuous time series. These different types of data, however, can now be complemented by palaeoclimate models, which determine climate system changes through given boundary conditions and changes caused through forcings. Such models help thus to identify the underlying mechanisms of observed climatic variations, and e to the extent that signal and noise can be distinguished e make it possible to separate the externally-forced climate signal from internal variability. In the following sections, those periods and areas that have proved to be most interesting in terms of potential linkages between climatic changes and socio-economic processes are discussed in chronological order. In the ninth century, the expansion of agriculture (Fig. 5) and the increase in monetary circulation (Fig. 2) signalled the economic recovery of Byzantine Anatolia, which culminated during the eleventh century. As indicated by the three archives of Nar G olü (Cappadocia), Sofular (Paphlagonia) and Uzuntarla (Thrace) Caves (Figs. 1 and 9) and also the lower temporally resolved record of Tecer Lake (Cappadocia), a marked shift from drier to wetter conditions seems to have occurred at the beginning of this period. This is in agreement with the CMIP5/PMIP3 models that denote wetter conditions for the Aegean/Anatolia at the same time (Fig. 11). The widespread abundance of rainfall must have resulted in more favourable conditions for agriculture in Anatolia in the ninth and tenth century. However, given the close relationship between political stability in Anatolia and agricultural expansion (Figs. 2 and 5) (Izdebski et al., 2015), the climatic conditions cannot be considered as the sole causal factor in respect of economic prosperity, even if they certainly contributed substantially to these processes. It seems far more likely that such a change in the region during the eleventh century should be attributed to human factors rather than fl uctuations in climate. Later than in Anatolia and at a slower pace, southern Greece (see also Fig. 1) experienced an expansion of agriculture (Fig. 5), reaching a climax after ca. AD 1150, followed by continuing settlement growth beyond the twelfth century (Fig. 3). The beginning of this period coincides with the economic recovery after the early medieval crisis and the later eighth century, which is particularly apparent in the increase in monetary circulation from the middle of the ninth century (Fig. 2). It should be noted that the later recovery in southern Greece, in comparison with that in Anatolia (Fig. 5), is probably related to its re-integration into the Byzantine empire in the ninth century, following which there took place a gradual political stabilisation (Table 1). The climatic conditions in southern Greece in the period ca. AD 900 e 1100 can be characterised as relatively wet, as indicated by the stable high effective humidity levels at Uzuntarla Cave and other independent palaeoclimate evidence (Fig. 9). Climate simulations (Fig. 11), as shown, are partly in agreement with this palaeoclimatic picture. The decade from around AD 920 e 930 represents an unusual period in terms of socio-economic instability and the available documentary record of severe famines (Kaplan, 1992, pp. 461 e 462) is quite clear, and these shifts had signi fi cant implications for the state's fi scal system, for military recruitment and for the relationship between the government and the power elite at Constantinople and the increasingly independent provincial elites (Morris, 1976; Frankopan, 2009; Haldon, 2009). This period was characterised by stronger snow accumulation as reconstructed from the Kocain Cave record (Fig. 9), and an increased frequency of cold winters in the Byzantine lands that show winter temperature conditions very close to the levels of the Little Ice Age (Fig. 15). Such conditions could be linked to the short-term subsistence crises reported by the historical sources for the AD 920s. From the economic point of view, the twelfth century seems to have been the most prosperous period for southern Greece, with high agricultural productivity, signi fi cant monetary exchange, and demographic expansion. This is the period during which the Byzantine empire, having made a signi fi cant recovery after the problems that had arisen in the second half of the eleventh century, was relatively strong in terms of political/military power (Table 1). But it is also a period characterised by generally drier conditions (Uzuntarla Cave, Sofular Cave, Nar G olü, Fig. 9) and high SSTs (M2, Gogou et al., in revision), as well as strong May e June precipitation variability, and a clear downward rainfall trend, as can be seen by the Aegean oak tree-rings reconstruction (Fig. 9). A ...

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... extended winter dryness is also shown by the CMIP5 models ( Fig. 11), especially for the period AD 1175 e 1200 (Fig. 15). Byzantine society in southern Greece during the twelfth century seems, in consequence, to be relatively resilient in a context of less favourable climatic conditions. In the tenth century, monetary circulation (Fig. 2) and cereal cultivation gradually expanded in both Bulgaria and northern Greece (Fig. 5). The relatively stable and also high SSTs from M2 together with the high humidity levels of the Uzuntarla Cave (Fig. 9) suggest that higher temperatures and more abundant precipitation facilitated the northward expansion of the Byzantine agricultural-economic pattern. However, the end of the eleventh century is marked by a drop in temperature and precipitation, as indicated by the north Aegean marine core M2, and Uzuntarla Cave (Thrace). Around AD 1100, a signi fi cant decrease in monetary circulation in Bulgaria (Fig. 2) seems decoupled from agricultural development, which continued without interruption (Fig. 5). The reasons for this are probably to be located in the differential impact of Pecheneg incursions from central Asia at this period, which may well have disrupted markets and monetised exchange activity without impacting in an obvious way on peasant production. The pollen data re fl ect a wider regional development, in contrast to the indicators for monetary exchange, which in this instance seem to re fl ect developments north of the Haemus range, thus areas most exposed to economic disruption (Frankopan, 1997; Stephenson, 1999). The models indicate a general reduction of rainfall in northern Greece and a drop towards the end of the eleventh century to the levels of the Little Ice Age in two of the simulations (Fig. 11), while the warm season is characterised by a tendency towards drier conditions. It should be noted that the twelfth century is characterised by generally dry conditions and this is evident in the palaeoclimate records of Nar G olü, Uzuntarla Cave and Sofular Cave (Fig. 9). Following the Turkish conquest and occupation of the Anatolian plateau (Table 1) and for almost the entire twelfth century, palaeoclimate records (Nar G olü, Uzuntarla Cave and Sofular Cave) in the eastern Mediterranean point to drier conditions almost everywhere across the Byzantine empire (Fig. 9). An important decline in agricultural production seems to have occurred in Anatolia already prior to AD 1100. The invasion of the Seljuks and the migration of the Turkoman nomads into central Anatolia after AD 1071 appear to have caused a serious retrenchment in the established economic system, while at the same time as these events were taking place, the region also had to cope with lower rainfall. Interestingly, whereas there is a clear decline in cereal cultivation over much of Anatolia (Fig. 5), the annually-resolved Nar G olü pollen data show only small-scale and short-term fl uctuations in cereal and pasturing-related pollen (England et al., 2008). This could suggest that the impact of both climate as well as human activity (such as raiding warfare, for example) depended on local environmental conditions, agricultural practices (cf. Crumley, 1994) and the nature of local social organization. Finally, the Seljuk expansion into the Middle East may have been encouraged by particularly cool climatic conditions over central Asia in the early eleventh century. Bulliet (2009) showed that cooling had a more dramatic impact on nomadic Seljuk society than on neighbouring sedentary cultures, since Seljuk camels were temperature-sensitive, and cooling forced a migration from the northern to the southern fringes of the Kar- akum desert. But there has as yet been no clear demonstration that climate was instrumental in the Seljuk invasion of Anatolia (cf. Ellenblum, 2012, and its reviews by Frankopan, 2013, and Burke, 2013) and more research is required in this direction. These unstable and rather dry conditions, especially during the second half of the twelfth century prevailed also in Greece and Macedonia, where economic growth continued throughout the whole century (Figs. 2 e 5). The contrast between the Anatolian and Greek parts of the Byzantine socio-economic system suggests that it was generally resilient to medium-scale climate fl uctuations, as well as to increased interannual variability, except where there also occurred signi fi cant political problems. In other words, since Byzantine Greece and Macedonia did not directly suffer from the Seljuk invasion of Anatolia, the agrarian economies of these regions of the Byzantine Empire coped quite well with the climatic stress of the twelfth century. The period of AD 1175/1180 e 1200, preceding the fall of Constantinople in AD 1204 and the partial collapse of the Byzantine state, was one during which the empire experienced considerable internal instability (Magdalino, 2008). In addition, a major rebellion in the central Balkans led to the creation of the so-called Second Bulgarian empire (Ritter, 2013). The question arises as to whether there was indeed a climatic dimension to these historical developments that could have limited the resources available to the Byzantine imperial government and increased social tensions. In fact, the empire did experience “ unusual ” climatic conditions during precisely these years. Dry conditions are indicated by all palaeoproxy records, on both sides of the Aegean Sea (Fig. 9 and Cook et al., in revision). Palaeomodels and the Euro_Med Consortium (in revision) summer temperature reconstruction also show clearly the prevalence of colder summers across virtually all three decades that preceded the fall of Constantinople in AD 1204 (Table 1). More speci fi cally, the tree-ring based May e June rainfall reconstructions and information from the Uzuntarla and Sofular Caves (Fig. 9) point to drier conditions over the greater North Aegean area. Additionally, data from Kocain Cave show a higher frequency of cold and likely drier winters. Finally, Nar G olü (Fig. 9) indicates rainier summers for the last decades of the twelfth century. Fig. 17 presents the average proportion of olive pollen for the highlands of Macedonia. A period of growth in the values of olive pollen in this part of Macedonia occurred during the ninth and tenth century. Given that wind can transport olive pollen over longer distances (Bottema and Woldring, 1990), this trend must re fl ect a general increase in the presence of olive trees (hence, expanding olive cultivation) over a larger area in the north ...

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... major elements of the agricultural regime and any larger-scale expansion of rural settlement necessarily involved their cultivation (Stathakopoulos, 2004) as they provided 40 e 50% of the annual calori fi c intake of a typical Byzantine diet (Kaplan, 1992, pp. 25 e 32; Bourbou et al., 2011). Poor cereal harvests e especially when repeated within a short period of time e could lead to subsistence crises on a regional or even larger scale. In such contexts, the state would draw less tax income from agricultural produce and such cases were sometimes associated with social upheaval accompanying food shortage. Byzantine textual sources emphasise the importance of regular rainfall from November until April for cereal farming, and in particular of the late autumn rains (Psellus, Peri georgikon, ed. Boissonade, 1829, and Geoponica, ed. Beckh, 1895, I 5; cf. Teall, 1971 on Geoponica ). Cereal fi elds were usually harvested in June or July (Kaplan, 1992, pp. 56 e 61). Yields were dependent on adequate rain during the spring growing season as well on weather conditions during the sowing in autumn. Wet and warm conditions before the oncoming winter would be effective for the seed germination and good vernalisation (Geoponica, ed. Beckh, 1895, II 14). Wine was popular among all strata of Byzantine society, widely traded and probably the most attractive cash crop during the Middle Ages. Little is known in detail of the operation and daily management of such estates, although evidence from magnate wills, from later monastic archives, especially for the period from the eleventh century on, and occasional references to matters of estate management in letters give some indication (Frankopan, 2009 and relevant sections in Laiou, 2002 and Laiou and Morrisson, 2007). Entire estates, villages or even small regions specialised in wine production (Harvey, 1989, pp. 146 e 147 and Kaplan, 1992, pp. 69 e 73). Representing only 5 e 10% of the total calori fi c input, a bad grape harvest could not lead to a subsistence crisis. On a shorter time scale (i.e., 3 e 5 years), however, poor grape harvests could affect an estate owner, a farmer or a region that relied economically on wine production. Recurring poor harvests, over a longer period of time (i.e., 10 years) and over a wider region could lead to a signi fi cant transformation of the agricultural regime, pressure on the social structure of a region, and likely to economic decline. Byzantine farmers were fully aware of the importance of climatic conditions for the cultivation of vine, in particular of the role that sunshine in combination with moderate temperatures had in achieving a good harvest (e.g., Geoponica, ed. Beckh, 1895, V 4, VII 1). A major threat that could lead to a complete loss of the annual grape harvest was the occurrence of hoar frost late in the spring. Other factors that in fl uenced harvest outcomes included the excessive summer heat and the late summer rain that affect grapes and consequently the quality of wine (Geoponica, ed. Beckh, 1895, V 36 and 43, 3). Like wine, olive oil was an important element of the Byzantine diet, and it had some share in the total calori fi c input. It was also traded on a relatively large scale and estates or villages often specialised in olive cultivation (Lefort, 2002; Mitchell, 2005). Accord- ing to documentary evidence, olives grow best in a dry climate (Geoponica, ed. Beckh, 1895, IX 3). Interestingly, information on unfavourable weather conditions for olive cultivation is found only in Byzantine narrative sources (Telelis, 2008), but not in the agronomic literature. A prolonged period of temperatures below À 10 C can, however, substantially damage olive trees (Tous and Ferguson, 1996). But it is likely that such conditions were not considered as a major threat to regions where the olive was grown, and that their perceived frequency was much lower than weather events that were dangerous to viticulture. The tax income of the Byzantine state was directly linked to agricultural output on a medium-term basis (decades). Several taxes were calculated according to the size of households, or the number of animals owned by a taxpayer. However, the key source of the state's income was the land tax which was calculated on the basis of the soil quality and the type of cultivated crop (Harvey, 1989, pp. 102 e 113 and Oikonomid es, 1996, pp. 42 e 121). In the ninth century AD, this tax provided the greater part of the state's income (Morrisson, 1991; Oikonomid es, 1996, pp. 24 e 41). A single year or a sequence of very bad years could result in dif fi culties for taxpayers and, consequently, social tensions and a reduction in fi scal income. The state sometimes acknowledged such unusually low annual or multi-annual yields, and the resultant inability of the taxpayers to pay their dues, or even the malnutrition and hunger of the peasants. In such cases, substantial tax exemptions could be granted, such as during the great famine of AD 928 (Kaplan, 1992, pp. 461 e 462; Morris, 1976). In addition, from the tenth century AD the state progressively became the largest secular estate owner and, along with the church, organised directly the cultivation of its own lands (Oikonomid es, 1991), thus becoming itself directly vulnerable to lower yields. The economic history of Byzantium during the MCA can be studied making use of a wide range of evidence (Fig. 1, Table 3). Historical (textual) sources contain qualitative information about long-term changes of the economic situation. Quantitative data originate from archaeological and palaeoenvironmental research conducted on speci fi c sites in the Balkans and Anatolia (Fig. 1). Archaeological fi eld surveys and excavation data provide information on i) numbers and values of coins found on sites and ii) numbers of sites per period within a surveyed region. In this way, archaeology offers direct data on the changes in the intensity of monetary exchange that took place in the cities and in the density of settlements in the countryside. Among the palaeoenvironmental evidence, pollen records from different parts of the medieval Byzantine world are the most important source of information about local and regional agricultural activity. Changes in the proportions of pollen of anthropogenic plants, such as cereals, vine, and olive, provide information about the vegetation structure of a given area in the past and thus can be used as some indication of the scale of the agricultural activity around a given site (Eastwood, 2006; Bottema and Woldring, 1990), in addition to the climate information that the pollen data also contain (e.g., Barboni et al., 2004; Brewer et al., 2007; Li et al., 2008; Luterbacher et al., 2012 and references therein and Kaniewski et al., 2013, 2014). All these data provide information about phenomena within the medieval Byzantine economy (monetary exchange, demographic growth, agricultural activity), but they do this in different ways and, most importantly, with different temporal resolutions. Textual evidence on economic activity gives only a very approximate impression of the economic trends and, consequently, only longer- term developments can be considered. Coins are dated either by the regnal years or, at a much lower resolution, by the reigns of individual emperors. Such data has a temporal resolution of approximately 50 years, as is visible in Fig. 2. Data on rural settlements are based on the chronologies of pottery that do not usually allow a temporal span of less than a century, and remain contro- versial (Vroom, 2005). Finally, the pollen data we use here are often characterised by a relatively low temporal resolution, except for ...

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Holocene alluvial dynamics, soil erosion and settlement in the uplands of Macedonia (Greece): New geoarchaeological insights from Xerolakkos in Grevena

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Jun 2024

This paper addresses the interplay between Holocene landscape evolution and human settlement dynamics, drawing new evidence from the alluvial history of Xerolakkos, a continental stream in Grevena (Western Macedonia, Greece). We developed an integrated geoarchaeological survey combining remote sensing geomorphological mapping, litho-stratigraphic analysis and radiocarbon dating with the site evidence of a new archaeological survey. Results revealed four major alluviation phases, corresponding to 1) the beginning of the Holocene until the Early Neolithic (~6300/6200 BCE), 2) the end of the Early and the Middle Neolithic (~6000–5400 BCE), 3) from the Middle Bronze Age to the Late Roman period (~1800 BCE – 500 CE), and 4) during the Byzantine and Ottoman eras (~500–1800 CE), all separated by phases of floodplain incision. Furthermore, the effects of several Holocene Rapid Climatic Changes (RCC) are traced and discussed together with potential human responses; we also provide the first alluvial sequence recording the ~6200 BCE (8.2 kyr BP) event in the Balkans. While the climate and the local geomorphological setting are considered the primary drivers behind instability and erosion during the Early and Middle Holocene, a landscape change starting in the Middle Bronze Age (after ~1800 BCE) followed by a re-organisation of the rural economy in the Roman period suggests the increasing involvement of anthropogenic forcing which, by the Ottoman period, evolved into a dynamic situation between climatic variability and adaptive land management. Finally, we demonstrate how soil erosion in the upper catchment constitutes a serious taphonomic bias when studying the regional archaeological record.

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Apr 2024
HOLOCENE

The analysis of the ASTC1 sediment core from the south Aegean Sea region offers critical insights into the complex interplay of geological and climatic factors over the Holocene period. The data reveals fluctuating climatic conditions during the last 8.7 ka as seen through the elemental concentrations obtained by XRF core scanning combined with a qualitative mineral analysis within a robust chronological framework. Short-term fluctuations in both Ti/Al and Zr/Si ratios suggest brief oscillations of increased aridity which partially coincide with the Holocene “Rapid Climate Change” events (RCCs). Among them, the most pronounced in our record are those centered between 8.5–8 ka, 3–2.5 ka (Greek Dark Ages), and 0.6–0.3 ka (Little Ice Age). The arid and humid events identified in the sediment record align with major archaeological periods in Greece, suggesting a potential influence of climatic conditions on the development and decline of civilizations in the region. Moreover, a general arid trend as of 6 ka toward the present was evidenced in our record and aligns with other high-resolution climatic data from the Northern Hemisphere, suggesting climatic teleconnections. Spectral analysis of the ASTC1 record reveals cyclical climate patterns with periodicities of approximately 2500, 1200, and 550 years, which coincide with the Bond and Hallstatt cycles. The phase relation of these cycles in our record, the Greenland ice record, and the North Atlantic Drift ice indices show that colder conditions in the higher latitudes are expressed as events of enhanced aridity in our record and generally in the lower latitudinal regions.

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Oct 2023
PLOS ONE

Based on records of the bottom elevations of 511 ancient water wells from published archaeological reports, we reconstructed the paleo-groundwater levels (PGWL) in urban areas of Chengdu, Changsha, Nanjing, Suzhou, Suqian, Yancheng, Fuzhou, and Guangzhou cities in southern China. Our PGWL reconstruction shows that PGWL varied in two patterns. In the inland monsoon region (Chengdu and Changsha), there was a low PGWL in Jin (AD 266–420) and South Song (AD 1127–1279), and a high PGWL in Tang (AD 618–907) and Ming (AD 1368–1644). In the coastal region (Yancheng, Fuzhou, and Guangzhou), there was a low PGWL in Jin (AD 266–420) and Ming (AD 1368–1644) but a high PGWL in Tang (AD 618–907) and Song (AD 960–1279). Via cross-wavelet transform and wavelet transform coherence analyses, we found that monsoon and temperature significantly drove the PGWL fluctuations at the inter-centennial scale. East Asian Summer Monsoon-induced precipitation has continuously affected cities in the inland monsoon area represented by Chengdu and Changsha over the past 2,500 years. It has also intermittently affected Nanjing and Suzhou when EASM intensified. In parallel, temperature influenced the PGWL in coastal cities such as Yancheng, Fuzhou, and Guangzhou via the changes in the sea level. Also, the temperature affected the PGWL in relatively inland cities during climatic anomalies such as the Medieval Warm Period and Little Ice Age. This study demonstrates the value of archaeological records in learning how climatic factors influence the PGWL variation and its mechanism.

A Late Holocene climate reconstruction from the high-altitude Lake Gölcük sedimentary records, Isparta (SW Anatolia)

Article

Jun 2023
QUATERNARY RES

A high-resolution multiproxy lake sediment dataset, comprising lithology, radiography, μXRF elemental, magnetic susceptibility (MS), δ ¹³ C, and δ ¹⁸ O measurements since ca. AD 400 is presented in this study. Changes in lithology, radiography, magnetic susceptibility (MS), δ ¹³ C, and δ ¹⁸ O reflect wet/dry climate periods, whereas variability in log(Ca/K) can reflect warm/cold climate periods. Analyses of the multiproxy results allow the distinction of several climate periods, which may be associated with climatic phenomena such as changes in North Atlantic Oscillation (NAO) and/or solar activity. The influence of NAO−/NAO+ (negative/positive) is suggested to be related with the southward/northward displacement of the storm tracks resulting from the NAO−/NAO+ phases. For solar activity, the influence is explained through a direct increase in solar heating leading to calcite precipitation. The Dark Ages Cold Period (DACP, AD 450–750) reflects cold-dry climate conditions at this site, indicative of a positive North Atlantic Oscillation (NAO+) and low solar activity. The Medieval Climate Anomaly (MCA, AD 950–1250) exhibits wet-dry-wet and warm-cold-warm climate conditions. The wet/dry periods likely are associated with NAO−/NAO+, respectively, and the warm/cold period may reflect relatively high/low solar activity. The Little Ice Age (LIA, AD 1400–1850) is characterized by dry and cold climate conditions, suggesting the influence of NAO+ and low solar activity. Comparison of the results of this study with local and regional results suggests a generally similar climate pattern, which is indicative of similar climate mechanisms. The contradictions can be associated with age-related uncertainties, orographic differences, and/or other regional teleconnections.

1,400 Years of Climate Change in the Northern Hemisphere

Preprint

Full-text available

Jan 2023

Marco Morando

Anthropogenic Global Warming is the Climate Change main cause. Nevertheless, several authors indicated the solar activity and the Atlantic Multi-decadal Oscillation variation as additional forcing. This article considers the amplification of the solar radiation and of the Atlantic Multi-decadal Oscillation’s variation, via sea ice cover albedo feedbacks in the Arctic regions, as forcing Climate change in complement to Anthropogenic Global Warming. A physical model, using the sunspot number count and the Atlantic Multi-decadal Oscillation index as inputs, simulates the average global temperature anomaly and the Arctic Sea Ice Extension for the past twelve centuries. This model represents innovative progress in understanding how existing studies on Arctic Sea ice’s albedo feedbacks can help complement the Anthropogenic Global Warming models, thus helping to define more precise models for future climate change. In addition, the North Atlantic Oscillation index across 1,200 years is determined and, through its correlation with temperature and precipitation anomaly, the climate history of 15 different European and Northern Hemisphere regions is modelled. The results are then compared with quantitative and qualitative benchmarks from the literature, to evaluate their level of accuracy in simulating the historical data. For purpose of simplicity, the model does not consider anthropogenic global warming. Nevertheless, the natural forcing described in this article shall be considered complementary to anthropogenic global warming effects. Manmade forcing will be included in a future model to be developed by the author.

Tools and Approaches to Addressing the Climate-Humans Nexus during the Holocene

Chapter

Jan 2023

Landscape Response to Dynamic Human Pressure in the Paliouras Lagoon, Halkidiki Peninsula, Macedonia, Greece

Article

Full-text available

Dec 2022

High-resolution pollen analysis of a sediment core recovered from Paliouras lagoon (Greece) allowed us to reconstruct the environmental dynamics of the Halkidiki peninsula during the last 4000 years. Palynological results have been interpreted and compared with detailed historical data, showing distinct phases of human-landscape interactions from the Bronze Age until recent times. Pollen spectra revealed an environment characterized by Mediterranean vegetation, mixed deciduous forest, and pine stands from the Late Bronze Age until the 11th century CE. The first signs of human impact were attested during the Archaic period with the cultivation of Olea, Castanea, and Vitis in the inland of the study area. An intensive land management was highlighted by arboriculture and cereal cultivation (Secale and Hordeum group) in Roman times. Late Antique-Early Medieval times coincided with less human pressure due to warfare-related crises, leading to the expansion of the forest and the abandonment of fields colonized by Amaranthaceae. A massive increase in pastoral activities, suggested by the high percentages of Cichorieae during the Ottoman period, is possibly linked to the significant demographic growth of the nearby city of Thessaloniki in the 16th century CE.

Byzantine Empire Economic Growth: Did Past Climate Change Play a Role?

Article

Full-text available

Aug 2022
HUM ECOL

Thomas Lambert

Different chronicles of the Byzantine Empire's history have noted various economic data gleaned from historical documents and accounts of the Empire's existence. I provide conjectures on approximate real GDP per capita for the Empire over its existence from AD 300 to 1453. I use these to investigate whether climate forcing variables are associated with real GDP per capita fluctuations. Some hypotheses on factors that would have affected Byzantine economic performance are tested using climate/environmental factors in time series regression. The results support and confirm some findings on how the Byzantine economy may have been affected by periods of regional climate change. Supplementary information: The online version contains supplementary material available at 10.1007/s10745-022-00343-3.

Mid-late Holocene vegetation history of the Argive Plain (Peloponnese, Greece) as inferred from a pollen record from ancient Lake Lerna

Article

Full-text available

Jul 2022
PLOS ONE

This study provides a high-resolution reconstruction of the vegetation of the Argive Plain (Peloponnese, Greece) covering 5000 years from the Early Bronze Age onwards. The well dated pollen record from ancient Lake Lerna has been interpreted in the light of archaeological and historical sources, climatic data from the same core and other regional proxies. Our results demonstrate a significant degree of human impact on the environments of the Argive Plain throughout the study period. During the Early Bronze Age evidence of a thermophilous vegetation is seen in the pollen record, representing the mixed deciduous oak woodland of the Peloponnesian uplands. The plain was mainly used for the cultivation of cereals, whereas local fen conditions prevailed at the coring site. Towards the end of this period an increasing water table is recorded and the fen turns into a lake, despite more arid conditions. In the Late Bronze Age, the presence of important palatial centres modified the landscape resulting in decrease of mixed deciduous oak woodland and increase in open land, partly used for grazing. Possibly, the human management produced a permanent hydrological change at Lake Lerna. From the Archaic period onwards the increasing human pressure in association with local drier conditions caused landscape instability, as attested by a dramatic alluvial event recorded in the Pinus curve at the end of the Hellenistic Age. Wet conditions coincided with Roman times and favoured a forest regeneration pattern in the area, at the same time as we see the most intensive olive cultivation in the pollen record. The establishment of an economic landscape primarily based on pastures is recorded in the Byzantine period and continues until modern times. Overgrazing and fires in combination with arid conditions likely caused degradation of the vegetation into garrigue, as seen in the area of the Argive Plain today.

Climate Change and Weather Extremes in the Eastern Mediterranean and Middle East

Article

Full-text available

Jul 2022
REV GEOPHYS

Observation‐based and modeling studies have identified the Eastern Mediterranean and Middle East (EMME) region as a prominent climate change hotspot. While several initiatives have addressed the impacts of climate change in parts of the EMME, here we present an updated assessment, covering a wide range of timescales, phenomena and future pathways. Our assessment is based on a revised analysis of recent observations and projections and an extensive overview of the recent scientific literature on the causes and effects of regional climate change. Greenhouse gas emissions in the EMME are growing rapidly, surpassing those of the European Union, hence contributing significantly to climate change. Over the past half‐century and especially during recent decades, the EMME has warmed significantly faster than other inhabited regions. At the same time, changes in the hydrological cycle have become evident. The observed recent temperature increase of about 0.45°C per decade is projected to continue, although strong global greenhouse gas emission reductions could moderate this trend. In addition to projected changes in mean climate conditions, we call attention to extreme weather events with potentially disruptive societal impacts. These include the strongly increasing severity and duration of heatwaves, droughts and dust storms, as well as torrential rain events that can trigger flash floods. Our review is complemented by a discussion of atmospheric pollution and land‐use change in the region, including urbanization, desertification and forest fires. Finally, we identify sectors that may be critically affected and formulate adaptation and research recommendations toward greater resilience of the EMME region to climate change.

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