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Combined with other westerly-sensitive records, a new stalagmite hydroclimate record from northern Italy reveals changing westerly wind directions over the past 6500 years that correspond to a migration of the North Atlantic centres of action.

A new stalagmite record from northern Italy and other published data from Europe and northern Africa reveals a split in the climatological westerlies during the early LIA, possibly attributed to sea ice melting.

Here the authors show that extremes in the summer jet stream position over Europe create a beech forest productivity dipole between northwestern and southeastern Europe and can result in regional anomalies in forest carbon uptake and growth.

Abstract Understanding changes in water availability is critical for Central Asia; however, long streamflow reconstructions extending beyond the period of instrumental gauge measurements are largely missing. Here, we present a 785-year-long streamflow reconstruction from spruce tree rings from the Tien Shan Mountains. Although an absolute causal relationship can not be established, relatively high streamflow rates coincided roughly with the period of Mongol expansion from 1225 to 1260 CE and the rise of the Timurid Empire from 1361 to 1400 CE. Since overall wetter conditions were further found during the Zunghar Khanate period 1693–1705 CE, we argue that phases of streamflow surplus likely promoted oasis and grassland productivity, which was an important factor for the rise of inner Eurasian steppe empires. Moreover, we suggest that the streamflow variation might be critical for plague outbreaks in Central Asia, and propose several explanations for possible links with Europe’s repeated Black Death pandemics. We demonstrate that 20th-century low streamflow is unprecedented in the past eight centuries and exacerbated the Aral Sea crisis, which is one of the most staggering ecological disasters of the twentieth century.

Abstract Fire regimes in North American forests are diverse and modern fire records are often too short to capture important patterns, trends, feedbacks, and drivers of variability. Tree‐ring fire scars provide valuable perspectives on fire regimes, including centuries‐long records of fire year, season, frequency, severity, and size. Here, we introduce the newly compiled North American tree‐ring fire‐scar network (NAFSN), which contains 2562 sites, >37,000 fire‐scarred trees, and covers large parts of North America. We investigate the NAFSN in terms of geography, sample depth, vegetation, topography, climate, and human land use. Fire scars are found in most ecoregions, from boreal forests in northern Alaska and Canada to subtropical forests in southern Florida and Mexico. The network includes 91 tree species, but is dominated by gymnosperms in the genus Pinus. Fire scars are found from sea level to >4000‐m elevation and across a range of topographic settings that vary by ecoregion. Multiple regions are densely sampled (e.g., >1000 fire‐scarred trees), enabling new spatial analyses such as reconstructions of area burned. To demonstrate the potential of the network, we compared the climate space of the NAFSN to those of modern fires and forests; the NAFSN spans a climate space largely representative of the forested areas in North America, with notable gaps in warmer tropical climates. Modern fires are burning in similar climate spaces as historical fires, but disproportionately in warmer regions compared to the historical record, possibly related to under‐sampling of warm subtropical forests or supporting observations of changing fire regimes. The historical influence of Indigenous and non‐Indigenous human land use on fire regimes varies in space and time. A 20th century fire deficit associated with human activities is evident in many regions, yet fire regimes characterized by frequent surface fires are still active in some areas (e.g., Mexico and the southeastern United States). These analyses provide a foundation and framework for future studies using the hundreds of thousands of annually‐ to sub‐annually‐resolved tree‐ring records of fire spanning centuries, which will further advance our understanding of the interactions among fire, climate, topography, vegetation, and humans across North America.

Accounting for 41.7% of China’s total land area, grasslands are linked to the livelihoods of over 20 million people. Although grassland fires cause severe damage in China every year, their spatiotemporal patterns and climate drivers are not well understood. In this study, we used grassland fire record forms provided by the National Forestry and Grassland Administration and grassland fire location data from the Wildfire Atlas of China to examine the spatiotemporal patterns and and seasonality of fires in China for the period from 2008 to 2020. We found that most grassland fires occurred in Inner Mongolia in northern China, specifically in the Hulun Buir and Xilingol grasslands. We found distinct differences in fire seasonality in northern China, which has a major fire season in April, versus southwestern China, where the major fire season occurs in February, March and April. April grassland fires in northern China are the result of strong winds, typically from the west, and spring drought. A secondary fire season in northern China occurs in October and is also driven by strong winds. The fire season in southwestern China seems to be less shaped by climatic factors such as wind speed, precipitation, and drought. This study provides support for decision-making by fire prevention and fire management authorities in China.