Aims: Until the late 19th century, Plasmodium vivax malaria was endemic in most of Europe including in the Nordic countries. In Denmark, Finland, and Sweden, the fluctuations in malaria cases and malaria-attributed deaths are known to have been associated with weather conditions, in particular with mean summer temperature variations. However, to what extent other environmental factors could have increased or decreased the risk of malaria has not previously been evaluated using historical records. Methods: In this study, we illustrate the non-linear association between different environmental variables (temperature, precipitation, and sea-level variations) and symptom-based malaria (case and death) data, using the quasi-Poisson distributed lag non-linear model. The robustness of the model results was examined through sensitivity analysis. Results: The modeling results showed that the risk associated with temperature increased by ∼25% in Denmark and by ∼67% in Sweden and Finland, with a mean summer temperature increase from 16°C to 18°C, was highest at 1–2 lagged years. Furthermore, average precipitation could have a noticeable effect on the malaria risk in Sweden and Finland, but this effect was not observed in Denmark. Environmental perturbations associated with extreme sea levels (>99.7th percentile or <0.1th percentile), including subsequent saltwater intrusion, could lead to increasing malaria risk in low-lying coastal areas. Conclusions: The historical evidence and modeling results suggest that specific weather conditions and extreme events have substantial impacts on malaria in temperate regions.

Climate variability and change, as well as extreme weather events, have notable impacts on human health and mortality. In historical times, the effect of climate on health and mortality was stronger than today, owing to factors such as poor housing and healthcare, along with the nutrition status that was meditated through climatic impacts on food production. Despite this, climatic impacts on mortality in the past remain poorly understood. This study aims to improve the understanding of climate effects on mortality using annual mortality records and meteorological data from Sweden between 1749 and 1859. The analysis includes the entire population, as well as subgroups based on sex and age. A statistically significant negative correlation was found between late winter and spring temperatures and mortality (i.e. lower temperatures equal higher mortality, and vice versa). We demonstrate that colder late winter and spring seasons were linked to higher mortality levels, not only for the same year but also for the following year. Conversely, no statistically significant associations were observed between summer or autumn temperatures and mortality, and only weak associations existed with hydroclimate. The impact of late winter and spring season temperature on mortality was most pronounced for the same year in southern Sweden and during the 19th century but stronger for the following year in central Sweden and during the 18th century. These findings call for further research, especially with respect to investigating specific diseases and additional factors contributing to the observed increase in mortality following cold late winter and spring seasons in Sweden during the late pre-industrial period.

Med ett varmare klimat dör fler på jorden till följd av hetta. Men hittills har den globala uppvärmningen fört med sig en större minskning av köldrelaterad dödlighet än ökning av värmerelaterad dödlighet.

De närmast apokalyptiska bränderna i Los Angeles har inneburit enorma materiella och ekonomiska förluster. Erfarenheter från stora historiska skogsbränder förebådar att de dessutom lär leda till en rad långsiktiga hälsokonsekvenser, av en sällan skådad omfattning.

The Qin and Western Han dynasties (221 BCE to 24 CE) represent an era of societal prosperity in China. However, due to a lack of high-resolution paleoclimate records it is still unclear whether the agricultural boost documented for this period was associated with more favorable climatic conditions. Here, multiparameter analysis of annually resolved tree-ring records and process-based physiological modeling provide evidence of stable and consistently humid climatic conditions during 270 to 77 BCE in northern China. Precipitation in the Asian summer monsoon region during the Qin–Western Han Dynasties was ~18 to 34% higher compared to present-day conditions. In shifting agricultural and pastoral boundaries ~60 to 100 km northwestward, possibility up to 200 km at times, persistently wetter conditions arguably increased food production, contributing to the socioeconomic prosperity around 2,200 y ago. A gradual wetting trend in the western part of arid northwestern China since the 1980s resembles the historical climate analogue, suggesting that similar benefits for regional environmental and agricultural systems may reoccur under current climate change, at least in the near term.

In central and southern Europe, grapevine is a climate-sensitive agricultural product of great economic importance, both in historical times and today. We systematically investigated the climatic impact, focusing on volcanic-forced abrupt cooling, on two long annual records of wine production quantity (spanning 1444-1786) from the Moselle Valley in present-day Luxembourg, close to the northern limit of viticulture in Europe. We present a consistent picture of the impact of volcanic eruptions on wine production through climate. To this end, we applied superposed epoch analysis - an appropriate method for detecting episodic signals in non-stationary time series - in combination with a bootstrap procedure to estimate the statistical significance. We also assessed the long-term relationship between different annual and seasonal climate parameters and wine production in the Moselle Valley. Robust and highly significant wine production declines occurred in the years immediately following major volcanic events. Warmer and, to a lesser extent, drier climate conditions had a moderately strong, but persistent, positive effect on wine production. We also find a volcanic cooling signature in spring and summer in temperature reconstructions. However, the detected volcanic signature in the Moselle Valley wine production is considerably stronger than the one found for central Europe in tree-ring-based reconstructions and is instead more akin to the strong volcanic signature present in Fennoscandian tree-ring series. On the basis of our findings, we encourage further compilation, publication, and analyses of additional wine production series containing unique biological and climatic information.

På måndag svärs Donald Trump in som USA:s 47:e president. Historikern och geografen Fredrik Charpentier Ljungqvist noterar att USA blir allt mer heterogent till skillnad från EU som blir allt mer homogent.

Groundwater dynamics are often overlooked within historical climatology because of their complexity and the influence of multiple factors. This study presents a groundwater model for Spain, using an existing tree-ring based summer drought reconstruction to estimate the groundwater depth in Castile and Leon (northwestern Spain) over the 1056-2020 CE period. Spanish groundwater volume fluctuations are found to be associated with quasi-decadal variations in the North Atlantic and Pacific Oceans. The reconstructed annual groundwater depth shows significant oscillations around a mean value of 123 m. Changes in groundwater depths include a wet medieval period ( similar to 1056-1200 CE), recurring megadroughts during parts of the Little Ice Age (similar to 1471-1600 CE), and unprecedentedly large variations during recent decades. Aligning with previous studies for the Iberian Peninsula, our new modelling approach highlights the need to enhance groundwater resilience in anticipation of potentially worsening future drought trends across the Mediterranean.

Historical documents provide evidence for regional droughts preceding the political turmoil and fall of Beijing in 1644 CE, when more than 20 million people died in northern China during the late Ming famine period. However, the role climate and environmental changes may have played in this pivotal event in Chinese history remains unclear. Here, we provide tree-ring evidence of persistent megadroughts from 1576 to 1593 CE and from 1628 to 1644 CE in northern China, which coincided with exceptionally cold summers just before the fall of Beijing. Our analysis reveals that these regional hydroclimatic extremes are part of a series of megadroughts along the Pacific Rim, which not only impacted the ecology and society of monsoonal northern China, but likely also exacerbated external geopolitical and economic pressures. This finding is corroborated by last millennium reanalysis data and numerical climate model simulations revealing internally driven Pacific sea surface temperature variations and the predominance of decadal scale La Niña-like conditions to be responsible for precipitation decreases over northern China, as well as extensive monsoon regions in the Americas. These teleconnection patterns provide a mechanistic explanation for reoccurring drought spells during the late Ming Dynasty and the environmental framework fostering the fall of Beijing in 1644 CE, and the subsequent demise of the Ming Dynasty.