Accurate water mapping depends largely on the water index. However, most previously widely-adopted water index methods are developed from 30-m resolution Landsat imagery, with low-albedo commission error (e.g., shadow misclassified as water) and threshold instability being identified as the primary issues. Besides, since the shortwave-infrared (SWIR) spectral band (band 11) on Sentinel-2 is 20 m spatial resolution, current SWIR-included water index methods usually produce water maps at 20 m resolution instead of the highest 10 m resolution of Sentinel-2 bands, which limits the ability of Sentinel-2 to detect surface water at finer scales. This study aims to develop a water index from Sentinel-2 that improves native resolution and accuracy of water mapping at the same time. Support Vector Machine (SVM) is used to exploit the 10-m spectral bands among Sentinel-2 bands of three resolutions (10-m; 20-m; 60-m). The new Multi-Spectral Water Index (MuWI), consisting of the complete version and the revised version (MuWI-C and MuWI-R), is designed as the combination of normalized differences for threshold stability. The proposed method is assessed on coincident Sentinel-2 and sub-meter images covering a variety of water types. When compared to previous water indexes, results show that both versions of MuWI enable to produce native 10-m resolution water maps with higher classification accuracies (p-value < 0.01). Commission and omission errors are also significantly reduced particularly in terms of shadow and sunglint. Consistent accuracy over complex water mapping scenarios is obtained by MuWI due to high threshold stability. Overall, the proposed MuWI method is applicable to accurate water mapping with improved spatial resolution and accuracy, which possibly facilitates water mapping and its related studies and applications on growing Sentinel-2 images.

Aim: The long‐term cyclical patterns of China's geopolitical shifts are of great interest to scholars and the public, but to date there has been no satisfactory explanation for the alternating occupancy patterns of the country's pastoral and agrarian polities. We fill this gap by differentiating the agroecological settings of these polities over time and quantitatively analysing the relationships between climate change and historical geopolitical variations.Location: China.Methods: Our dataset comprised 38 palaeohydroclimate reconstructions, the historical boundaries of China's empire and the changes in its size, and 1028 wars and 2737 battle locations over the past 2300 years. China‐wide precipitation during the period was reconstructed using the ‘weighted composite plus scale’ method. Time‐series analyses were performed to identify the strength of the associations between climate change and the geopolitical variables. Granger causality analysis and wavelet analysis were performed to verify the hypothesized causal links. Wavelet analysis was also used to identify the possible interactions (i.e. frequencies, significance, consistency and synchrony) between the signal components of the climatic and geopolitical variables at different temporal scales.Results: China's mean precipitation fell into three multicentennial cycles. The geopolitical variables corresponded to those cycles in the imperial era. The spatial–temporal frequencies of the boundaries and size of the agriculturalist empires and its frontiers with pastoralist empires were regulated by the long‐term (low‐frequency) precipitation fluctuations at the multicentennial scale. Wars of aggression were an important explanatory factor driving the land‐occupancy patterns of the two ecoempires under climate change, and caused most of the territorial shifts. Short‐term (high‐frequency) geopolitical changes were not associated with climate change.Main conclusions: Precipitation‐induced ecological change was an important factor governing the macrogeopolitical cycles in imperial China. Long‐term territorial expansion favoured the polity (agriculturalist or pastoralist) that was better adapted to the changing ecological conditions in the country's heartland.

At Quesang on the Tibetan Plateau we report a series of hand and foot impressions that appear to have been intentionally placed on the surface of a unit of soft travertine. The travertine was deposited by water from a hot spring which is now inactive and as the travertine lithified it preserved the traces. On the basis of the sizes of the hand and foot traces, we suggest that two track-makers were involved and were likely children. We interpret this event as a deliberate artistic act that created a work of parietal art. The travertine unit on which the traces were imprinted dates to between ∼169 and 226 ka BP. This would make the site the earliest currently known example of parietal art in the world and would also provide the earliest evidence discovered to date for hominins on the High Tibetan Plateau (above 4000 m a.s.l.). This remarkable discovery adds to the body of research that identifies children as some of the earliest artists within the genus Homo.

Effective adaptation determines agricultural vulnerability to climate change, especially in the pre-industrial era. Crop management as an agricultural adaptation to climate change in recent human history, however, has rarely been systematically evaluated. Using Europe as our study area, we statistically compared yield ratio of wheat, rye, barley, and oats (an important performance indicator of an agrarian economy) between Eastern and Western Europe in AD 1500–1800. In particular, a statistical comparison was made of crop yield ratio in the two regions during the warm agricultural recovery period AD 1700–1800. The general trend of crop yield in Eastern and Western Europe basically followed the alternation of climatic epochs, in which the extreme cooling period in AD 1560–1660 drastically reduced the crop yield ratio. The yield ratio of rye in Eastern and Western Europe was very similar throughout the entire study period. However, the yield ratio of wheat, barley, and oats showed different patterns in the two regions and increased drastically in Western Europe in the warm agricultural recovery period, which might have contributed to rapid socio-economic development in Western Europe and eventually the East–West Divide in Europe in the following centuries.