The Summer North Atlantic Oscillation, Arctic sea ice, and Arctic jet Rossby wave forcing.

We use Coupled Model Intercomparison Project Phase 6 (CMIP6) coupled and Atmospheric Model Intercomparison Project (AMIP) climate models, dynamical analyses, and observations to investigate interactions between summer Arctic sea ice concentration (SIC) variations and the Summer North Atlantic Oscillation (SNAO). Observations suggest that SIC-SNAO relationships mainly come from the East Siberian to Arctic Canada (ESAC) region where a weak atmospheric jet stream exists in summer. Twelve CMIP6 models with the most realistic atmospheric climatologies over the North Atlantic and Europe agree well with reanalyses on relationships between SIC and Northern Hemisphere atmospheric circulation.

Coupled Pacific Rim megadroughts contributed to the fall of the Ming Dynasty's capital in 1644 CE.

Historical documents provide evidence for regional droughts preceding the political turmoil and fall of Beijing in 1644 CE, when more than 20 million people died in northern China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.

Legacy of last millennium timber use on plant cover in Central Europe: Insights from tree rings and pollen.

Throughout history, humans have relied on wood for constructions, tool production or as an energy source. How and to what extent these human activities have impacted plant abundance and composition over a long-term perspective is, however, not well known. To address this knowledge gap, we combined 44,239 precisely dated tree-ring samples from economically and ecologically important tree species (spruce, fir, pine, oak) from historical buildings, and pollen-based plant cover estimates using the REVEALS model from 169 records for a total of 34 1° × 1° grid cells for Central Europe.

Optimal Strategy on Radiation Estimation for Calculating Universal Thermal Climate Index in Tourism Cities of China.

The Universal Thermal Climate Index (UTCI) is believed to be a very powerful tool for providing information on human thermal perception in the domain of public health, but the solar radiation as an input variable is difficult to access. Thus, this study aimed to explore the optimal strategy on estimation of solar radiation to increase the accuracy in UTCI calculation, and to identify the spatial and temporal variation in UTCI over China. With daily meteorological data collected in 35 tourism cities in China from 1961 to 2020, two sunshine-based Angstrom and Ogelman models, and two temperature-based Bristow and Hargreaves models, together with neural network and support vector machine-learning methods, were tested against radiation measurements.

The negative impact of increasing temperatures on rice yields in southern China.

China is the main producer and consumer of rice in the world, and rice is a major staple food grain for more than half of the world's population. Reduced rice yields caused by climate factors not only affect the food security of China, but also has global repercussions. Thus, it is vital to assess the potential impact of climate warming on rice production.

The spatiotemporal distribution of historical malaria cases in Sweden: a climatic perspective.

Background: Understanding of the impacts of climatic variability on human health remains poor despite a possibly increasing burden of vector-borne diseases under global warming. Numerous socioeconomic variables make such studies challenging during the modern period while studies of climate-disease relationships in historical times are constrained by a lack of long datasets. Previous studies have identified the occurrence of malaria vectors, and their dependence on climate variables, during historical times in northern Europe.

Abrupt shift to hotter and drier climate over inner East Asia beyond the tipping point.

Unprecedented heatwave-drought concurrences in the past two decades have been reported over inner East Asia. Tree-ring-based reconstructions of heatwaves and soil moisture for the past 260 years reveal an abrupt shift to hotter and drier climate over this region. Enhanced land-atmosphere coupling, associated with persistent soil moisture deficit, appears to intensify surface warming and anticyclonic circulation anomalies, fueling heatwaves that exacerbate soil drying.

Impacts of Drought on Maize and Soybean Production in Northeast China During the Past Five Decades.

Climate change has a distinct impact on agriculture in China, particularly in the northeast, a key agriculture area sensitive to extreme hydroclimate events. Using monthly climate and agriculture data, the influence of drought on maize and soybean yields-two of the main crops in the region-in northeast China since 1961 to 2017 were investigated. The results showed that the temperature in the growing season increased by 1.

Spatial risk assessment of global change impacts on Swedish seagrass ecosystems.

Improved knowledge on the risk in ecologically important habitats on a regional scale from multiple stressors is critical for managing functioning and resilient ecosystems. This risk assessment aimed to identify seagrass ecosystems in southern Sweden that will be exposed to a high degree of change from multiple global change stressors in mid- and end-of-century climate change conditions. Risk scores were calculated from the expected overlap of three stressors: sea surface temperature increases, ocean acidification and wind driven turbid conditions.

Temporal variability of a protected multispecific tropical seagrass meadow in response to environmental change.

In a changing environment, there is an increasing interest to monitor ecosystems to understand their responses to environmental change. Seagrass meadows are highly important ecosystems that are under constant pressure from human activities and climate impacts, with marked declines observed worldwide. Despite increasing efforts, monitoring of multispecific tropical seagrass meadows is scarce, particularly in low-income regions.

Agricultural Adaptation to Global Warming in the Tibetan Plateau.

The Tibetan plateau is one of the most sensitive areas in China and has been significantly affected by global warming. From 1961 to 2017, the annual air temperature increased by 0.32 °C/decade over the Tibetan Plateau, which is the highest in the whole of China.

The influence of excess precipitation on winter wheat under climate change in China from 1961 to 2017.

Winter wheat is one of China's most important staple food crops, and its growth and productivity are influenced by climate. Given its importance, we investigated the influence of excess precipitation under recent climate change on winter wheat in east-central China during 1961-2017. Although annual precipitation in the studied region decreased slightly, it increased during the winter wheat flowering and maturity period (May to June).

Tree rings reveal globally coherent signature of cosmogenic radiocarbon events in 774 and 993 CE.

Though tree-ring chronologies are annually resolved, their dating has never been independently validated at the global scale. Moreover, it is unknown if atmospheric radiocarbon enrichment events of cosmogenic origin leave spatiotemporally consistent fingerprints. Here we measure the C content in 484 individual tree rings formed in the periods 770-780 and 990-1000 CE.

ARCTIC CHANGE AND POSSIBLE INFLUENCE ON MID-LATITUDE CLIMATE AND WEATHER: A US CLIVAR White Paper.

Unlabelled: The Arctic has warmed more than twice as fast as the global average since the mid 20th century, a phenomenon known as Arctic amplification (AA). These profound changes to the Arctic system have coincided with a period of ostensibly more frequent events of extreme weather across the Northern Hemisphere (NH) mid-latitudes, including extreme heat and rainfall events and recent severe winters. Though winter temperatures have generally warmed since 1960 over mid-to-high latitudes, the acceleration in the rate of warming at high-latitudes, relative to the rest of the NH, started approximately in 1990.

Recent enhancement of central Pacific El Niño variability relative to last eight centuries.

The far-reaching impacts of central Pacific El Niño events on global climate differ appreciably from those associated with eastern Pacific El Niño events. Central Pacific El Niño events may become more frequent in coming decades as atmospheric greenhouse gas concentrations rise, but the instrumental record of central Pacific sea-surface temperatures is too short to detect potential trends. Here we present an annually resolved reconstruction of NIÑO4 sea-surface temperature, located in the central equatorial Pacific, based on oxygen isotopic time series from Taiwan tree cellulose that span from 1190 AD to 2007 AD.

Climate Change Increases Drought Stress of Juniper Trees in the Mountains of Central Asia.

Assessments of climate change impacts on forests and their vitality are essential for semi-arid environments such as Central Asia, where the mountain regions belong to the globally important biodiversity hotspots. Alterations in species distribution or drought-induced tree mortality might not only result in a loss of biodiversity but also in a loss of other ecosystem services. Here, we evaluate spatial trends and patterns of the growth-climate relationship in a tree-ring network comprising 33 juniper sites from the northern Pamir-Alay and Tien Shan mountain ranges in eastern Uzbekistan and across Kyrgyzstan for the common period 1935-2011.

Old World megadroughts and pluvials during the Common Era.

Climate model projections suggest widespread drying in the Mediterranean Basin and wetting in Fennoscandia in the coming decades largely as a consequence of greenhouse gas forcing of climate. To place these and other "Old World" climate projections into historical perspective based on more complete estimates of natural hydroclimatic variability, we have developed the "Old World Drought Atlas" (OWDA), a set of year-to-year maps of tree-ring reconstructed summer wetness and dryness over Europe and the Mediterranean Basin during the Common Era. The OWDA matches historical accounts of severe drought and wetness with a spatial completeness not previously available.

Spatial variability and temporal trends in water-use efficiency of European forests.

The increasing carbon dioxide (CO2 ) concentration in the atmosphere in combination with climatic changes throughout the last century are likely to have had a profound effect on the physiology of trees: altering the carbon and water fluxes passing through the stomatal pores. However, the magnitude and spatial patterns of such changes in natural forests remain highly uncertain. Here, stable carbon isotope ratios from a network of 35 tree-ring sites located across Europe are investigated to determine the intrinsic water-use efficiency (iWUE), the ratio of photosynthesis to stomatal conductance from 1901 to 2000.

A comparison of growing season indices for the Greater Baltic Area.

Predictions of the effects of global warming suggest that climate change may have large impacts on ecosystems. The length of the growing season is predicted to increase in response to increasing global temperatures. The object of this study was to evaluate different indices used for calculating the thermal growing season for the Greater Baltic Area (GBA).

Comparison of some criteria for diagnosing a myocardial infarction after aorto-coronary bypass grafting (CABG).

The incidence of myocardial infarction during a 1-year follow-up period after coronary bypass surgery (CABG), i.e. a recent myocardial infarction (RMI), was studied in 86 patients.

Hereditary myopathy with lactic acidosis, succinate dehydrogenase and aconitase deficiency in northern Sweden: a genealogical study.

A hereditary myopathy with lactic acidosis during physical exercise, low physical work capacity, and paroxysmal myoglobinuria (HML), called "Myopathy with deficiency of succinate dehydrogenase and aconitase" (McKusick 255125) has been described in 19 members of nine families who lived in two geographically separate areas in northern Sweden. By using the unique Swedish historical archives, including Catechetical Meeting Records from a number of northern Swedish parishes, it has been possible to trace ancestors of the nine families including all known 19 cases back in time to some key couples, who lived up to 300 years ago (that is seven to ten generations). No common single couple or common links between families in the past was found in these registers as a support for a single or several mutations that had developed far back in time.

Effects of digitalis, anti-anginal drugs and arterial hypertension on the relationships between exercise ECG and angiocardiographic variables and on the diagnostic accuracy of exercise ECG in patients with coronary heart disease.

We have previously found a statistically significant correlation between some exercise ECG variables and angiocardiographic scores used to evaluate the extent and type of coronary heart disease (CHD). In the present study we examined the effects of digitalis, beta-adrenergic blockers, slow release nitrates, calcium channel blockers, presence of arterial hypertension (AHT), and angiocardiographic changes on the exercise ECG variables. The effects of drugs and AHT were small as compared to the effects of the angiocardiographically detected pathological changes caused by the CHD.