Martin Karl Skoglund

Major volcanic eruptions have long been proposed to have triggered and amplified historical plague pandemics through climatic shocks and harvest failures, but the mechanisms linking volcanic forcing, nutrition and disease remain poorly quantified. We develop a theoretical model of a single region with zero spatial dimensions ("0-D") that couples volcanic forcing, climate, agricultural productivity, food storage, malnutrition and plague epidemiology. The epidemiological component includes reservoir hosts, vectors, human-to-human transmission, disease-driven migration and waning immunity, with transmission and mortality rates dependent on nutritional status. We first evaluate the model against agricultural and archaeological evidence from England following the 1345 CE eruption, shortly before the Second Plague Epidemic. The simulations reproduce the observed sudden drop in crop output and prolonged deterioration in nutritional conditions, as well as the observed relationship between plague mortality and an isotopic proxy for malnutrition derived from human skeletons. We then apply the model to the Justinianic Plague following the 536 and 540 CE eruptions. Representing three population groups with different vulnerability to harvest failure and malnutrition, the model predicts eventual plague mortality of about 39 %, consistent with historical estimates. Sensitivity experiments show that removing the effect of volcanic forcing on malnutrition substantially reduces predicted plague mortality, whereas excluding disease-driven migration increases it. Doubling eruption intensity produces only a modest increase in total mortality, revealing nonlinear interactions among climate, nutrition and epidemic dynamics. A reduced phase-space analysis further shows that epidemic feedbacks change from net positive to net negative as susceptible individuals are depleted, with the system transitioning from an initially unstable state towards a quasi-equilibrium attractor. Together, the simulations suggest that volcanic eruptions could have substantially amplified historical plague epidemics through their effects on failure of harvests and food production, malnutrition and human behaviour. The results provide a mechanistic framework linking volcanic climate forcing to epidemic severity and highlight nutrition as a potentially important mediator of climate–disease interactions.

Major volcanic eruptions have long been proposed to have triggered and amplified historical plague pandemics through climatic shocks and harvest failures, but the mechanisms linking volcanic forcing, nutrition and disease remain poorly quantified. We develop a theoretical model of a single region with zero spatial dimensions ("0-D") that couples volcanic forcing, climate, agricultural productivity, food storage, malnutrition and plague epidemiology. The epidemiological component includes reservoir hosts, vectors, human-to-human transmission, disease-driven migration and waning immunity, with transmission and mortality rates dependent on nutritional status. We first evaluate the model against agricultural and archaeological evidence from England following the 1345 CE eruption, shortly before the Second Plague Epidemic. The simulations reproduce the observed sudden drop in crop output and prolonged deterioration in nutritional conditions, as well as the observed relationship between plague mortality and an isotopic proxy for malnutrition derived from human skeletons. We then apply the model to the Justinianic Plague following the 536 and 540 CE eruptions. Representing three population groups with different vulnerability to harvest failure and malnutrition, the model predicts eventual plague mortality of about 39 %, consistent with historical estimates. Sensitivity experiments show that removing the effect of volcanic forcing on malnutrition substantially reduces predicted plague mortality, whereas excluding disease-driven migration increases it. Doubling eruption intensity produces only a modest increase in total mortality, revealing nonlinear interactions among climate, nutrition and epidemic dynamics. A reduced phase-space analysis further shows that epidemic feedbacks change from net positive to net negative as susceptible individuals are depleted, with the system transitioning from an initially unstable state towards a quasi-equilibrium attractor. Together, the simulations suggest that volcanic eruptions could have substantially amplified historical plague epidemics through their effects on failure of harvests and food production, malnutrition and human behaviour. The results provide a mechanistic framework linking volcanic climate forcing to epidemic severity and highlight nutrition as a potentially important mediator of climate–disease interactions.

Major volcanic eruptions have long been proposed to have triggered and amplified historical plague pandemics through climatic shocks and harvest failures, but the mechanisms linking volcanic forcing, nutrition and disease remain poorly quantified. We develop a theoretical model of a single region with zero spatial dimensions ("0-D") that couples volcanic forcing, climate, agricultural productivity, food storage, malnutrition and plague epidemiology. The epidemiological component includes reservoir hosts, vectors, human-to-human transmission, disease-driven migration and waning immunity, with transmission and mortality rates dependent on nutritional status. We first evaluate the model against agricultural and archaeological evidence from England following the 1345 CE eruption, shortly before the Second Plague Epidemic. The simulations reproduce the observed sudden drop in crop output and prolonged deterioration in nutritional conditions, as well as the observed relationship between plague mortality and an isotopic proxy for malnutrition derived from human skeletons. We then apply the model to the Justinianic Plague following the 536 and 540 CE eruptions. Representing three population groups with different vulnerability to harvest failure and malnutrition, the model predicts eventual plague mortality of about 39 %, consistent with historical estimates. Sensitivity experiments show that removing the effect of volcanic forcing on malnutrition substantially reduces predicted plague mortality, whereas excluding disease-driven migration increases it. Doubling eruption intensity produces only a modest increase in total mortality, revealing nonlinear interactions among climate, nutrition and epidemic dynamics. A reduced phase-space analysis further shows that epidemic feedbacks change from net positive to net negative as susceptible individuals are depleted, with the system transitioning from an initially unstable state towards a quasi-equilibrium attractor. Together, the simulations suggest that volcanic eruptions could have substantially amplified historical plague epidemics through their effects on failure of harvests and food production, malnutrition and human behaviour. The results provide a mechanistic framework linking volcanic climate forcing to epidemic severity and highlight nutrition as a potentially important mediator of climate–disease interactions.

Major volcanic eruptions have long been proposed to have triggered and amplified historical plague pandemics through climatic shocks and harvest failures, but the mechanisms linking volcanic forcing, nutrition and disease remain poorly quantified. We develop a theoretical model of a single region with zero spatial dimensions ("0-D") that couples volcanic forcing, climate, agricultural productivity, food storage, malnutrition and plague epidemiology. The epidemiological component includes reservoir hosts, vectors, human-to-human transmission, disease-driven migration and waning immunity, with transmission and mortality rates dependent on nutritional status. We first evaluate the model against agricultural and archaeological evidence from England following the 1345 CE eruption, shortly before the Second Plague Epidemic. The simulations reproduce the observed sudden drop in crop output and prolonged deterioration in nutritional conditions, as well as the observed relationship between plague mortality and an isotopic proxy for malnutrition derived from human skeletons. We then apply the model to the Justinianic Plague following the 536 and 540 CE eruptions. Representing three population groups with different vulnerability to harvest failure and malnutrition, the model predicts eventual plague mortality of about 39 %, consistent with historical estimates. Sensitivity experiments show that removing the effect of volcanic forcing on malnutrition substantially reduces predicted plague mortality, whereas excluding disease-driven migration increases it. Doubling eruption intensity produces only a modest increase in total mortality, revealing nonlinear interactions among climate, nutrition and epidemic dynamics. A reduced phase-space analysis further shows that epidemic feedbacks change from net positive to net negative as susceptible individuals are depleted, with the system transitioning from an initially unstable state towards a quasi-equilibrium attractor. Together, the simulations suggest that volcanic eruptions could have substantially amplified historical plague epidemics through their effects on failure of harvests and food production, malnutrition and human behaviour. The results provide a mechanistic framework linking volcanic climate forcing to epidemic severity and highlight nutrition as a potentially important mediator of climate–disease interactions.

Major volcanic eruptions have long been proposed to have triggered and amplified historical plague pandemics through climatic shocks and harvest failures, but the mechanisms linking volcanic forcing, nutrition and disease remain poorly quantified. We develop a theoretical model of a single region with zero spatial dimensions ("0-D") that couples volcanic forcing, climate, agricultural productivity, food storage, malnutrition and plague epidemiology. The epidemiological component includes reservoir hosts, vectors, human-to-human transmission, disease-driven migration and waning immunity, with transmission and mortality rates dependent on nutritional status. We first evaluate the model against agricultural and archaeological evidence from England following the 1345 CE eruption, shortly before the Second Plague Epidemic. The simulations reproduce the observed sudden drop in crop output and prolonged deterioration in nutritional conditions, as well as the observed relationship between plague mortality and an isotopic proxy for malnutrition derived from human skeletons. We then apply the model to the Justinianic Plague following the 536 and 540 CE eruptions. Representing three population groups with different vulnerability to harvest failure and malnutrition, the model predicts eventual plague mortality of about 39 %, consistent with historical estimates. Sensitivity experiments show that removing the effect of volcanic forcing on malnutrition substantially reduces predicted plague mortality, whereas excluding disease-driven migration increases it. Doubling eruption intensity produces only a modest increase in total mortality, revealing nonlinear interactions among climate, nutrition and epidemic dynamics. A reduced phase-space analysis further shows that epidemic feedbacks change from net positive to net negative as susceptible individuals are depleted, with the system transitioning from an initially unstable state towards a quasi-equilibrium attractor. Together, the simulations suggest that volcanic eruptions could have substantially amplified historical plague epidemics through their effects on failure of harvests and food production, malnutrition and human behaviour. The results provide a mechanistic framework linking volcanic climate forcing to epidemic severity and highlight nutrition as a potentially important mediator of climate–disease interactions.

Major volcanic eruptions have long been proposed to have triggered and amplified historical plague pandemics through climatic shocks and harvest failures, but the mechanisms linking volcanic forcing, nutrition and disease remain poorly quantified. We develop a theoretical model of a single region with zero spatial dimensions ("0-D") that couples volcanic forcing, climate, agricultural productivity, food storage, malnutrition and plague epidemiology. The epidemiological component includes reservoir hosts, vectors, human-to-human transmission, disease-driven migration and waning immunity, with transmission and mortality rates dependent on nutritional status. We first evaluate the model against agricultural and archaeological evidence from England following the 1345 CE eruption, shortly before the Second Plague Epidemic. The simulations reproduce the observed sudden drop in crop output and prolonged deterioration in nutritional conditions, as well as the observed relationship between plague mortality and an isotopic proxy for malnutrition derived from human skeletons. We then apply the model to the Justinianic Plague following the 536 and 540 CE eruptions. Representing three population groups with different vulnerability to harvest failure and malnutrition, the model predicts eventual plague mortality of about 39 %, consistent with historical estimates. Sensitivity experiments show that removing the effect of volcanic forcing on malnutrition substantially reduces predicted plague mortality, whereas excluding disease-driven migration increases it. Doubling eruption intensity produces only a modest increase in total mortality, revealing nonlinear interactions among climate, nutrition and epidemic dynamics. A reduced phase-space analysis further shows that epidemic feedbacks change from net positive to net negative as susceptible individuals are depleted, with the system transitioning from an initially unstable state towards a quasi-equilibrium attractor. Together, the simulations suggest that volcanic eruptions could have substantially amplified historical plague epidemics through their effects on failure of harvests and food production, malnutrition and human behaviour. The results provide a mechanistic framework linking volcanic climate forcing to epidemic severity and highlight nutrition as a potentially important mediator of climate–disease interactions.

The article investigates the 1783–1784 Laki flood lava eruption as a case of regionally differentiated volcanic climate impacts and compound climate–society shocks in the Nordic countries. Drawing on recent advances in paleoclimate reanalysis (ModE-RA), early instrumental weather observations, dendroclimatology, and local environmental histories, it reconstructs seasonal and spatial patterns of climate anomalies and their societal repercussions from Iceland to Finland. A model–data comparison reveals marked regionality: while ModE-RA indicates pronounced post-eruption cooling from 1784 to 1786, instrumental and proxy evidence show strong sub-regional contrasts, including a preceding unrelated severe spring–summer drought in southern Scandinavia and notable discrepancies between ensemble simulations and observed autumn 1783 and winter 1783/84 temperature patterns. The study conceptualizes the Laki crisis as a compound event in the Nordic countries, in which volcanic cooling interacted with antecedent warmth and drought, atmospheric pollution, societal tensions, and institutional vulnerabilities. Pre-eruption drought and grain harvest failures in Denmark and southern and central Sweden, eruption-related toxic haze and vegetation damage in Iceland, and subsequent cold seasons combined to produce cascading impacts on harvests, food prices, mortality, and social protest, with peak demographic and political effects lagging 2–3 years after the eruption and food crises. By systematically integrating “archives of nature” and “archives of society” across multiple Nordic polities, this study illustrates how an interdisciplinary climate history framework can capture the regional complexity of volcanic forcing and climatic anomalies, clarify tensions between models and observations, and explain divergent societal trajectories under compound climatic stress.

Major volcanic eruptions have long been proposed to have triggered and amplified historical plague pandemics through climatic shocks and harvest failures, but the mechanisms linking volcanic forcing, nutrition and disease remain poorly quantified. We develop a theoretical model of a single region with zero spatial dimensions ("0-D") that couples volcanic forcing, climate, agricultural productivity, food storage, malnutrition and plague epidemiology. The epidemiological component includes reservoir hosts, vectors, human-to-human transmission, disease-driven migration and waning immunity, with transmission and mortality rates dependent on nutritional status. We first evaluate the model against agricultural and archaeological evidence from England following the 1345 CE eruption, shortly before the Second Plague Epidemic. The simulations reproduce the observed sudden drop in crop output and prolonged deterioration in nutritional conditions, as well as the observed relationship between plague mortality and an isotopic proxy for malnutrition derived from human skeletons. We then apply the model to the Justinianic Plague following the 536 and 540 CE eruptions. Representing three population groups with different vulnerability to harvest failure and malnutrition, the model predicts eventual plague mortality of about 39 %, consistent with historical estimates. Sensitivity experiments show that removing the effect of volcanic forcing on malnutrition substantially reduces predicted plague mortality, whereas excluding disease-driven migration increases it. Doubling eruption intensity produces only a modest increase in total mortality, revealing nonlinear interactions among climate, nutrition and epidemic dynamics. A reduced phase-space analysis further shows that epidemic feedbacks change from net positive to net negative as susceptible individuals are depleted, with the system transitioning from an initially unstable state towards a quasi-equilibrium attractor. Together, the simulations suggest that volcanic eruptions could have substantially amplified historical plague epidemics through their effects on failure of harvests and food production, malnutrition and human behaviour. The results provide a mechanistic framework linking volcanic climate forcing to epidemic severity and highlight nutrition as a potentially important mediator of climate–disease interactions.

The article investigates the 1783–1784 Laki flood lava eruption as a case of regionally differentiated volcanic climate impacts and compound climate–society shocks in the Nordic countries. Drawing on recent advances in paleoclimate reanalysis (ModE-RA), early instrumental weather observations, dendroclimatology, and local environmental histories, it reconstructs seasonal and spatial patterns of climate anomalies and their societal repercussions from Iceland to Finland. A model–data comparison reveals marked regionality: while ModE-RA indicates pronounced post-eruption cooling from 1784 to 1786, instrumental and proxy evidence show strong sub-regional contrasts, including a preceding unrelated severe spring–summer drought in southern Scandinavia and notable discrepancies between ensemble simulations and observed autumn 1783 and winter 1783/84 temperature patterns. The study conceptualizes the Laki crisis as a compound event in the Nordic countries, in which volcanic cooling interacted with antecedent warmth and drought, atmospheric pollution, societal tensions, and institutional vulnerabilities. Pre-eruption drought and grain harvest failures in Denmark and southern and central Sweden, eruption-related toxic haze and vegetation damage in Iceland, and subsequent cold seasons combined to produce cascading impacts on harvests, food prices, mortality, and social protest, with peak demographic and political effects lagging 2–3 years after the eruption and food crises. By systematically integrating “archives of nature” and “archives of society” across multiple Nordic polities, this study illustrates how an interdisciplinary climate history framework can capture the regional complexity of volcanic forcing and climatic anomalies, clarify tensions between models and observations, and explain divergent societal trajectories under compound climatic stress.

The article investigates the 1783–1784 Laki flood lava eruption as a case of regionally differentiated volcanic climate impacts and compound climate–society shocks in the Nordic countries. Drawing on recent advances in paleoclimate reanalysis (ModE-RA), early instrumental weather observations, dendroclimatology, and local environmental histories, it reconstructs seasonal and spatial patterns of climate anomalies and their societal repercussions from Iceland to Finland. A model–data comparison reveals marked regionality: while ModE-RA indicates pronounced post-eruption cooling from 1784 to 1786, instrumental and proxy evidence show strong sub-regional contrasts, including a preceding unrelated severe spring–summer drought in southern Scandinavia and notable discrepancies between ensemble simulations and observed autumn 1783 and winter 1783/84 temperature patterns. The study conceptualizes the Laki crisis as a compound event in the Nordic countries, in which volcanic cooling interacted with antecedent warmth and drought, atmospheric pollution, societal tensions, and institutional vulnerabilities. Pre-eruption drought and grain harvest failures in Denmark and southern and central Sweden, eruption-related toxic haze and vegetation damage in Iceland, and subsequent cold seasons combined to produce cascading impacts on harvests, food prices, mortality, and social protest, with peak demographic and political effects lagging 2–3 years after the eruption and food crises. By systematically integrating “archives of nature” and “archives of society” across multiple Nordic polities, this study illustrates how an interdisciplinary climate history framework can capture the regional complexity of volcanic forcing and climatic anomalies, clarify tensions between models and observations, and explain divergent societal trajectories under compound climatic stress.