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.

Decadal-scale climate predictability is crucial for societal planning, not least in regions sensitive to winter extremes. This study predicts the number of heavy snowfall days in the Swiss Pre-Alpine Region (SPAR) through 2060, using a time-varying autoregressive model based on data from 1884 to 2023. The model integrates a pattern index that combines both large-scale (Arctic Oscillation and Dipole Model Index) and regional-scale (spring–winter temperature differential) climate forcings, capturing lagged seasonal effects. The results indicate a slight upward trend – about one to two additional heavy snowfall days by the 2050s – though not statistically significant, and consistent with regionally downscaled climate models. After 2045, variability is expected to rise, periods of snowfall deficits affecting year groups and a cluster of exceedance years emerging towards the end of the projection period. While extreme snowfall events are projected to become less frequent in the Northern Hemisphere, their intensity is unlikely to diminish. These findings enhance understanding of snowfall dynamics in the SPAR and contribute to broader insights into cryospheric changes. Data-driven models such as this one are valuable tools to contextualise historical hydroclimatic drivers and assessing inter-annual and inter-decadal variability in regional climate projections and their societal implications.

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.

En gång var stora delar av Amazonas ett landskap format av människan. Med hjälp av ny teknik upprättar forskare i dag tredimensionella kartor över försvunna civilisationer – och upptäcker sanningen bakom missionärernas berättelser om vägar och städer djupt inne i regnskogen.

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.

Desertification threatens livelihoods and sustainable development in dryland areas, with its risks further intensified by climate change and human activities. However, its extent and severity remain insufficiently quantified across global, regional, and national scales. Here we integrate annual aridity-index-based dryland classifications to indicate potential desertification areas, apply land cover conversion to bare areas to identify desertified areas, and use high-resolution population data to estimate both the number and spatial distribution of populations exposed to desertification at multiple scales. Between 2001 and 2018, the global desertified area increased by 5,387.8 ± 383.5 km² yr⁻¹, while the exposed population grew by 126,857 ± 6,723 people yr⁻¹. Population exposure exhibits pronounced spatial heterogeneity, particularly at the national level. As desertified areas expand, more people, who lack the resources to migrate, become increasingly dependent on degraded land, thereby further accelerating land degradation. This self-reinforcing feedback loop complicates efforts to achieve land degradation neutrality by 2030, as outlined in the United Nations Sustainable Development Goals. By explicitly incorporating hyper-arid areas and linking ecosystem service loss with population exposure, this study develops a cross-scale analytical framework that enhances the assessment of desertification exposure and offers new insights into global desertification risks.

Radial growth of trees is highly sensitive to environmental changes, but the effect of climate on tree rings in Qinghai spruce (Picea crassifolia), a widely distributed endemic conifer in western China, is more complex than in many other conifers. A comprehensive understanding of the spatiotemporal climatic responses of its rings is needed to develop theoretical basis for designing strategies for its conservation and management. Here, our synthesis of the literature on responses of radial growth of Qinghai spruce to monthly climate variables in different environmental conditions by meta-analysis showed that precipitation and drought severity are the main limiting factors for Qinghai spruce radial growth in the semiarid region of northwestern China. In warmer and drier areas, radial growth of Qinghai spruce is mainly limited by drought. In the areas north of the 600-mm annual precipitation isoline, the tree-ring width (TRW) was significantly positively correlated with precipitation and significantly negatively correlated with temperature during the growing season (June–August). The limiting effect of drought on Qinghai spruce is also gradually increasing from southeast to northwest, to the west of 103° E and within 37° N–39° N.

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.

The 8.2 and 4.2 ka BP abrupt climate events had significant impacts on Earth’s climate system. However, the spatio-temporal pattern of these events remains ambiguous in the East Asian summer monsoon (EASM) region. In this study, we collected thirteen previously published stalagmite δ¹⁸O sequences from the EASM region to assess spatial and temporal patterns of the 8.2 and 4.2 ka BP events during the ∼8.7–7.7 ka BP and ∼4.7–3.7 ka BP periods, respectively. Our results reveal that high-resolution stalagmite δ¹⁸O sequences from nearby locations exhibit strong consistency during the Holocene, thus capturing regional patterns of climate variability. Sensitivity experiments indicate that the temporal resolution and geographical location significantly affect the ability of the stalagmite δ¹⁸O sequences to record the 8.2 and 4.2 ka BP events. High-resolution stalagmite δ¹⁸O records from both northern and southern China show a distinct positive δ¹⁸O excursion corresponding with the 8.2 ka BP event, beginning at 8.23 ka BP and ending at 8.08 ka BP, thus lasting ∼150 yr, with an explained variance reaching ∼55% on centennial timescales. In contrast, there are significant north-south differences in the δ¹⁸O signal during the period ∼4.26–3.97 ka BP, with a shift from negative to positive δ¹⁸O values in northern China and a contrasting pattern in southern China. The application of the Monte Carlo empirical orthogonal function (MCEOF) method effectively reproduces the pronounced positive δ¹⁸O excursion during the period ∼8.7–7.7 ka BP and exhibits fluctuations based on the long-term increase in δ¹⁸O during the period ∼4.7–3.7 ka BP. The positive δ¹⁸O excursion during the 4.2 ka BP event is primarily contributed by stalagmites from southern China, in particular the Dongge and Heshang Caves. Our study highlights the importance of using multiple high-resolution climate records to assess abrupt events both in space and time.