George Adamson

Recent advances in the historical climatology of the tropics and subtropics

Recent years have seen major advances in the understanding of the historical climatology of tropical and subtropical areas, primarily through the analysis of documentary materials such as weather diaries, newspapers, personal correspondence, government records, and ship logs. This paper presents a critical review of these advances, drawing upon examples from across the tropics and subtropics. The authors focus in particular on the ways in which documentary evidence has been used to improve our understanding of 1) historical temperature variability, 2) fluctuations in annual and seasonal precipitation, and 3) the occurrence, severity, and impact of tropical cyclones. They also discuss the ways in which documentary evidence has been combined with information from natural archives to reconstruct historical El Nino and La Nina episodes. The article concludes with some suggestions for future research. These include the exploration of historical documents from hitherto under-researched regions and the applicati...

Critical pathway analysis to determine key uncertainties in net impacts on disease burden in Bangladesh of arsenic mitigation involving the substitution of arsenic bearing for groundwater drinking water supplies

It has been increasingly recognised that calculation of the disease burden due to populations, such as in Bangladesh, extensively using hazardous arsenic bearing well waters, must explicitly account for the trade-off between diarrhoeal disease incidence and that of arsenic-related diseases. This is because it is likely that moves to alternative drinking water sources, be they surface waters or even more distant groundwaters, without further mitigation would result in a concurrent increase in diarrhoeal disease. In this paper, we update the model of Lokuge[ 1 ] of the effects of such arsenic mitigation on disease burden in Bangladesh, using updated population data and background disease estimates. We run a critical pathway analysis on the model using Standardised Mortality Ratios (SMRs) for diabetes mellitus and ischemic heart disease from different epidemiological studies recently reviewed by Navas-Acien.[ 2 , 3 ] Our analysis agrees with that of Lokuge[ 1 ] that mitigation simply involving the substitution of a range of surface waters for well water sources with As > 50 μ g/L would have a net positive impact on disease burden, as determined by deaths and Disability Life Adjusted Years (DALYs). In contrast, however, there is considerable ambiguity in the analogous results for mitigation for all the population exposed to well water with As > 10 μ g/L. Depending upon the data source chosen for diabetes mellitus and ischaemic heart disease SMRs, such mitigation is modelled to have either a positive or a negative net impact on overall disease burden. The modelled negative impacts are entirely commensurate with the rationale for seeking groundwater as an alternative to surface waters as a drinking water supply, and highlight the practical requirement for multiple mitigation strategies, including those directed at ensuring the microbiological safety and continued protection of any alternative water supplies. Our study highlights the need for (i) adequate epidemiological studies involving multiple exposure categories, ideally resulting in an accurate dose-response relationship for arsenic uptake and the non-malignant high incidence conditions diabetes mellitus and ischemic heart disease for individuals with the socioeconomic and nutritional status of the Bangladeshi populations, and (ii) refined estimates of the diarrhoel disease burden arising from usage of surface waters.

Documentary reconstruction of monsoon rainfall variability over western India, 1781–1860

Investigations into the climatic forcings that affect the long-term variability of the Indian summer monsoon are constrained by a lack of reliable rainfall data prior to the late nineteenth century. Extensive qualitative and quantitative meteorological information for the pre-instrumental period exists within historical documents, although these materials have been largely unexplored. This paper presents the first reconstruction of monsoon variability using documentary sources, focussing on western India for the period 1781–1860. Three separate reconstructions are generated, for (1) Mumbai, (2) Pune and (3) the area of Gujarat bordering the Gulf of Khambat. A composite chronology is then produced from the three reconstructions, termed the Western India Monsoon Rainfall reconstruction (WIMR). The WIMR exhibits four periods of generally deficient monsoon rainfall (1780–1785, 1799–1806, 1830–1838 and 1845–1857) and three of above-normal rainfall (1788–1794, 1813–1828 and 1839–1844). The WIMR shows good correspondence with a dendroclimatic drought reconstruction for Kerala, although agreement with the western Indian portion of the tree-ring derived Monsoon Asia Drought Atlas is less strong. The reconstruction is used to examine the long-term relationship between the El Nino-Southern Oscillation (ENSO) and monsoon rainfall over western India. This exhibits peaks and troughs in correlation over time, suggesting a regular long-term fluctuation. This may be an internal oscillation in the ENSO-monsoon system or may be related to volcanic aerosol forcings. Further reconstructions of monsoon rainfall are necessary to validate this. The study highlights uncertainties in existing published rainfall records for 1817–1846 for western India.

‘The Most Horrible of Evils’: Social Responses to Drought and Famine in the Bombay Presidency, 1782–1857

Western peninsular India is subject to regular climate-related natural disasters, being highly sensitive to periodic droughts and flooding. This chapter draws on new reconstructions of monsoon rainfall intensity for the nineteenth century to explore social responses to drought in western India between 1782 and 1857. The analysis reveals a heavy mortality amongst pastoralist and peasant-farming communities, although this apparently diminished towards the middle of the nineteenth century. Measures adopted by vulnerable individuals to buffer against drought included crop rotation, rogation and recourse to loans from local moneylenders, with migration into urban areas and consumption of ‘famine crops’ reported during exceptionally strong droughts. Wealthy merchants and rulers apparently played a role in providing charitable support. However, traditional support structures were challenged with a move from indigenous to colonial governance in 1817, and the introduction of market-driven, laissez-faire drought policy.

El Niño in the Twentieth Century

This chapter addresses El Nino’s impact in the twentieth century, a century for which descriptions are uniquely detailed. The El Ninos in the twentieth century that are perhaps best known are 1982–1983 and 1997–1998, respectively the first event to attract global news coverage and the first to be correctly forecast. The El Nino of 1924–1925 is significant as the first to attract international scientific interest. Other El Ninos were notable for associated mortality: the El Nino of 1941–1942 was responsible for the last major famine in the Indian subcontinent and the El Nino of 1972–1973 brought drought and famine to the Sahel. In general, though, the twentieth century was notable for a significant reduction in mortality due to meteorological extremes associated with El Nino.

The Influence of El Niño on World Crises in the Nineteenth Century

The impact of El Nino events from the time of the French Revolution to the present day raises wider issues about the connections between climatic events, social disruption and revolution when one examines the colonial context. The new structures of colonialism and western economic penetration that occurred during the nineteenth century significantly affected vulnerability to El Nino events within colonised populations in drought-prone regions. Although people had always died in droughts in India or Africa, for example, the new governing structures often significantly challenged traditional responses to drought. As a result, in several regions mortality figures during El Nino-caused droughts during the nineteenth century increased above earlier levels. The nineteenth century, though, may have marked the culmination of global El Nino-related mortality.

El Niño Events and the History of Epidemic Disease Incidence

The history of El Nino incidence can help shed light on some aspects of the history of disease and epidemics. A comparison of the chronologies of severe El Nino events and the chronologies of major disease pandemics indicates close connections between the two patterns, particularly in the case of plague, malaria, cholera and influenza, probably the four biggest epidemic killers historically. Most of these epidemic diseases flourish in El Nino periods because their (mainly mosquito) vectors flourish in the changed hydrological conditions that are characteristic of El Nino occurrences. This information on historical El Nino now allows us, for the first time, to present a synthesis of the evidence linking El Nino with disease epidemics and an evaluation of the arguments for climatic agency.

The Discovery of ENSO

The Southern Oscillation was named in 1924 and its discovery can be traced back to colonial attempts to forecast the Indian monsoon in the late-nineteenth century. The first use of the name ‘El Nino’ to describe a climatic phenomenon appeared in South America in 1893. The term did not, however, originally mean what it does today, being used to describe a seasonal warm water current that is manifest off the coast of northwestern Peru. The history of these two distinct phenomena and their eventual amalgamation into ENSO is closely linked to the activities of the international Guano industry and to efforts to strengthen US soft power in Latin America during the Cold War. Significant advances in El Nino forecasting have occurred since the 1982 event.

El Niño Chronology and the Little Ice Age

Thanks to the work of Hubert Lamb the effect of climate on society in the Little Ice Age (LIA) is well known in temperate latitudes. The subtropical and tropical history of the LIA and its El Nino events is far less analysed or documented. It does seem clear that the most severe drought periods in Asia and elsewhere (especially Africa) that were manifest during the LIA were associated almost exclusively with what we consider to have been El Nino events. In this way we are then able to ask the question: what happened in the tropics, and especially in Asia, during the El Nino events of the LIA, and what does this mean in terms of understanding the history of economic patterns and human crises?

Postscript: El Niño and Human Future

One thing that has been missing from this book is the effect of climate change on El Nino. The primary reason for this is the large uncertainty that currently exists in the science of future El Nino. Changes to El Nino itself are uncertain, although changes to teleconnections are more likely. This is because the atmosphere responds much more quickly to rising greenhouse gas concentrations than do the oceans, which are slower at heating up. This postscript concludes with a discussion of the 2015-16 El Nino, which had unexpected characteristics and demonstrated the need for continued research on El Nino in the past and present.