Tephra layers in marine sediment cores from scientific ocean drilling largely record high‐magnitude silicic explosive eruptions in the Japan arc for up to the last 20 million years. Analysis of the thickness variation with distance of 180 tephra layers from a global data set suggests that the majority of the visible tephra layers used in this study are the products of caldera‐forming eruptions with magnitude (M) > 6, considering their distances at the respective drilling sites to their likely volcanic sources. Frequency of visible tephra layers in cores indicates a marked increase in rates of large magnitude explosive eruptions at ∼8 Ma, 6–4 Ma, and further increase after ∼2 Ma. These changes are attributed to major changes in tectonic plate interactions. Lower rates of large magnitude explosive volcanism in the Miocene are related to a strike‐slip‐dominated boundary (and temporary cessation or deceleration of subduction) between the Philippine Sea Plate and southwest Japan, combined with the possibility that much of the arc in northern Japan was submerged beneath sea level partly due to previous tectonic extension of northern Honshu related to formation of the Sea of Japan. Changes in plate motions and subduction dynamics during the ∼8 Ma to present period led to (1) increased arc‐normal subduction in southwest Japan (and resumption of arc volcanism) and (2) shift from extension to compression of the upper plate in northeast Japan, leading to uplift, crustal thickening and favorable conditions for accumulation of the large volumes of silicic magma needed for explosive caldera‐forming eruptions.

[1] The sulphur released by the 1815 Tambora volcanic eruption resulted in a net cooling after the eruption. The cold climate was responsible for crop failures, leading to serious famine and high food prices in Europe and North America. The year 1816 became known as the "year without summer". We performed a series of climate simulations with the UK Met Office model HadGEM2-ES to assess the climate and carbon cycle consequences of the eruption. The model shows a temperature decrease of 1˙0.1 ı C and global precipitation decrease of 3.7% in 1816. The following net primary productivity (NPP) increase is caused by strongly reduced plant respiration and supports the overall increase in land carbon storage after the eruption. Most of the carbon is taken up by the soil reservoir, mainly due to increased litter influx. Overall, the change of combined land and ocean carbon implies an atmospheric CO 2 decrease of over 6 ppmv. C3 and C4 grasses, used here as an analogy for crops, revealed globally increasing productivity for C3 grasses/crops (e.g., wheat) by 8%, while C4 grasses/crops (e.g., maize) decreased by over 12%. Regional positive C3 and negative C4 NPP are mainly found in the tropics and midlatitudes, whereas positive C4 NPP areas are distributed in marginal areas. Negative C3 grasses anomalies are found in high-elevation and high-latitude regions. These findings highlight the importance of including process-based vegetation or crop model components to represent the potentially nonlinear dependencies on climatic changes.

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Volcanic ash falls are one of the most widespread and frequent volcanic hazards, and are produced by all explosive volcanic eruptions. Ash falls are arguably the most disruptive volcanic hazard because of their ability to affect large areas and to impact a wide range of assets, even at relatively small thicknesses. From an insurance perspective, the most valuable insured assets are buildings. Ash fall vulnerability curves or functions, which relate the magnitude of ash fall to likely damage, are the most developed for buildings, although there have been important recent advances for agriculture and infrastructure. In this paper, we focus on existing vulnerability functions developed for volcanic ash fall impact on buildings, and apply them to a hypothetical building portfolio impacted by a modernday Tambora 1815 eruption scenario. We compare and contrast the different developed functions and discuss some of the issues surrounding estimation of potential building damage following a volcanic eruption. We found substantial variability in the different vulnerability estimates, which contribute to large uncertainties when estimating potential building damage and loss. Given the lack of detailed and published studies of building damage resulting from ash fall this is not surprising, although it also appears to be the case for other natural hazards for which there are far more empirical damage data. Notwithstanding the potential limitations of some empirical data in constraining vulnerability functions, efforts are required to improve our estimates of building damage under ash fall loading through the collection of damage data, experimental testing and perhaps theoretical failure analysis. For insurance purposes, the current building typologies provided for use with vulnerability functions are too detailed to map to the relatively limited information on building types that is typically available to insurers. Thus, efforts to provide vulnerability functions that can be used where only limited information is available regarding building types would also be valuable, both for insurers and for at-risk areas that have not been subject to detailed building vulnerability surveys.

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