Multi-proxy summer and winter precipitation reconstruction for southern Africa over the last 200 years

This study presents the first consolidation of palaeoclimate proxy records from multiple archives to develop statistical rainfall reconstructions for southern Africa covering the last two centuries. State-of-the-art ensemble reconstructions reveal multi-decadal rainfall variability in the summer and winter rainfall zones. A decrease in precipitation amount over time is identified in the summer rainfall zone. No significant change in precipitation amount occurred in the winter rainfall zone, but rainfall variability has increased over time. Generally synchronous rainfall fluctuations between the two zones are identified on decadal scales, with common wet (dry) periods reconstructed around 1890 (1930). A strong relationship between seasonal rainfall and sea surface temperatures (SSTs) in the surrounding oceans is confirmed. Coherence among decadal-scale fluctuations of southern African rainfall, regional SST, SSTs in the Pacific Ocean and rainfall in south-eastern Australia suggest SST-rainfall teleconnections across the southern hemisphere. Temporal breakdowns of the SST-rainfall relationship in the southern African regions and the connection between the two rainfall zones are observed, for example during the 1950s. Our results confirm the complex interplay between large-scale teleconnections, regional SSTs and local effects in modulating multi-decadal southern African rainfall variability over long timescales.     

Archival explorations of climate variability and social vulnerability in colonial Mexico

In this paper, unpublished archival documentary sources are used to explore the vulnerability to–and implications of–climatic variability and extreme weather events in colonial Mexico. Attention focuses on three regions covering a variety of environmental, social, economic, and political contexts and histories and located at key points along a north-south rainfall gradient: Chihuahua in the arid north, Oaxaca in the wetter south and Guanajuato located in the central Mexican highlands. A number of themes are considered. First, the significance of successive, prolonged, or combined climate events as triggers of agrarian crisis. Second, a case study demonstrating the national and regional impacts of a particularly devastating climate induced famine, culminating with the so-called ‘Year of Hunger’ between 1785 and 1786, is presented. The way in which social networks and community engagement were rallied as a means of fortifying social resilience to this and other crises will be highlighted. Third, the impacts of selected historical flood events are explored in order to highlight how the degree of impact of a flood was a function of public expectation, preparedness and also the particular socio-economic and environmental context in which the event took place. An overview of the spatial and temporal variations in vulnerability and resilience to climatic variability and extreme weather events in colonial Mexico is then provided, considering those recorded events that could potentially relate to broader scale, possibly global, climate changes.     

Exploring the role of the amateur in the production and circulation of meteorological knowledge

There is a growing scholarship on the role of the amateur, and amateur societies, in the production and circulation of weather and climate knowledge in the past. Yet relatively little attention has been paid to the actual and potential contribution of contemporary amateur meteorologists in this respect. In this paper we first examine the importance of the amateur historically in the production of local weather knowledge and also in the emergence of professional meteorology. Drawing on semi-structured interviews with members of one contemporary UK based amateur meteorological organisation??the Climatological Observers Link (COL)??we then investigate the nature and extent of contemporary amateur meteorologists?? contributions to a wide range of different ??publics?? today, which include both popular and professional communities. Finally, we interrogate our interview data to identify whether COL members themselves recognise a wider role for their expertise at a time of increasing popular and scientific interest in weather and climate and in an era when the inclusion of non-certified experts in policy decision making processes is being advocated.     

Drought, desiccation and discourse: missionary correspondence and nineteenth-century climate change in central southern Africa

This paper examines the role that representatives of the London Missionary Society in central southern Africa during the nineteenth century may have played in the development of geographical debates concerning the long-term desiccation of the African continent. Observations on climate included within missionary documents are used to reconstruct a chronology of intra-decadal climatic variability for the period 1815–1900. This reveals six drought periods and seven wet phases that affected large areas of the region, but identifies no evidence for progressive desiccation. The chronology is then used as a framework within which to view missionary perspectives on drought and desiccation. Major influences upon the development of desiccationist theory appear to include the prevalence of contemporary moral economic explanations of climatic variability, as well as the uptake and acceptance of indigenous understanding of climate change. Significantly, many of the key observations by eminent missionaries used as supporting evidence for progressive desiccation are identified as having been made during periods of severe drought. This is used to suggest that the most widely propagated evidence for desiccation may, therefore, simply be the end-product of periods of short-term drought rather than long-term climatic deterioration.     

Decades of Drought, Years of Hunger: Archival Investigations of Multiple Year Droughts in Late Colonial Chihuahua

Unusually severe or prolonged drought ranks among the most devastating and calamitous of all extreme climate events, contributing to wildfires, crop failure, livestock death, food shortages and famine. The response of human activities and the natural environment to such historical weather perturbations provides a guide to where the most critical sensitivities to future climate changes may lie (McCarthy et al., 2001, ‘Climatic change 2001: Impact adaptation, and vulnerability’, from 3rd Assesment Report of IPCC). The reconstruction of regional climatic histories and investigations of the impacts of – and social response to – extreme droughts in history are thus of crucial significance if we are to understand and anticipate the potential repercussions of future events (Wigley, 1985, Nature 316, 106–107; Grove and Conterio, 1995, Clim. Change 30, 223). Chihuahua, in the arid Northwest of Mexico, is one of the most seriously and frequently drought affected regions of the country (Garcia, 2000, available at www.sequia.edu.mx/proyectos/vulnera.html). Prolonged drought in the 1930s, 1950s and 1990s contributed to water scarcity, harvest failure, illness, livestock disease, abandonment and water conflict and served to highlight the particular vulnerability of agrarian society in this region to climatic variability (Sandoval, 2003, Ingeneria Hidraulica en Mexico 18(2), 133–155). Recent investigations using tree ring analysis have identified several phases of such prolonged drought over the last seven centuries. In this paper we use archival documents to investigate the impacts of such periods in late colonial Chihuahua and to explore how society in the region responded to and coped with them.     

‘Splendid rains have fallen’: links between El Niño and rainfall variability in the Kalahari, 1840–1900

This study uses a range of published and unpublished historical documentary sources to explore the nature of rainfall variability in the Kalahari Desert and adjacent hardveld regions of central southern Africa during the seventeen Pacific El Niño–Southern Oscillation (ENSO) episodes that occurred between 1840 and 1900. Documentary data are used in two ways. First, maps of relative annual rainfall levels are presented for each of the 12 single-year and five protracted ENSO episodes during the period, in order to identify the associated inter-annual rainfall variations. These suggest that the relationship between ENSO episodes and rainfall variability identified for the twentieth century, whereby warm events are frequently preceded by wetter conditions during the austral summer prior to the event year and succeeded by drought in the following summer, has broadly held for much of the last 160 years. This is despite the long-term fluctuations in precipitation and temperature which are known to have occurred over this period. Droughts are identified following at least thirteen of the 17 single-year and protracted ENSO episodes. Pre-ENSO wetter periods are less common, with only nine of the ENSO episodes preceded by above-normal rainfall. Second, the documentary data are analyzed in detail in order to reveal any evidence for high resolution intra-annual variations in the seasonal distribution of rainfall during ENSO events. Seasonal sequences of rainfall/drought appear to have closely followed contemporary patterns, with heavy rainfall commonly occurring late in the pre-ENSO year or early in the ENSO year(s), and drought at the start of the post-ENSO year. This relationship can be seen to hold most strongly for single-year ENSO warm events and for the first year of protracted events, but rainfall conditions were more variable during the later years of protracted events.     

Environmental changes in the Zirahuén Basin, Michoacán, Mexico, during the last 1000 years

Lago de Zirahuén (19° 26 N, 101° 44 W) lies within a montane basin in highland Michoacán, Mexico at 2075 m a.s.l. The lake basin has high recreational value and is promoted as a tourist attraction. Four short (<1 m), sediment–water interface cores were used to investigate Late Holocene environmental change. The cores span approximately the last 1000 years, based on ²¹⁰Pb dating, AMS ¹⁴C dating and tephrochronology. Cesium-137, Americium-241 and tephra layers from Volcan Paricutín (AD 1943–1952) and Volcan Jorullo (AD 1759–1774) provide independent age markers. Cores were analysed for diatoms, magnetic susceptibility and heavy metals (iron, lead, manganese, copper and zinc). Drier climate around 1000 years BP is tentatively inferred from the diatom assemblage and is concordant with other regional records. Increased soil erosion between ca. AD 1100 and AD 1550 may be associated with Pre-Hispanic settlement in the basin, but there is no archaeological evidence to support this. A period of catchment stability occurred during the early Colonial Period, ca. AD 1550–1750. The dramatic decline in the indigenous population following the Spanish Conquest in 1521 may have promoted vegetation recovery on the basin slopes. After the mid-18th century, a significant change in diatom species composition is observed along with an increase in soil erosion, as inferred from the magnetic susceptibility profile. Concentrations of copper and lead also increased. These changes are associated with the establishment of a copper smelting industry in the basin and increased Colonial agricultural development. Recently, tourist developments and commercial agriculture have impacted on the basin. The diatom flora has changed dramatically in the last 20 years, apparently in response to the onset of cultural eutrophication. The palaeoenvironmental evidence suggests that the lake is responding rapidly to land use intensification in the basin, which may have implications for future developments.     

Narratives of nineteenth century drought in southern Africa in different historical source types

Climatic Change - Single- to multiple-year drought episodes posed significant challenges for agrarian communities across southern Africa during the nineteenth century and hence are widely recorded...