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Climate changes and its influences on human society are of increasing concern in science communities. Based on the reconstructed climate data and CENTURY model, we simulated net primary productivity of grassland and the grain yield of highland barley during the pre-industrial millennium in Ali Prefecture, Tibet Autonomous Region. It showed that the variation of precipitation and temperature together affected the fluctuation of land productivity. Wavelet analysis results showed that the land productivity in Ali fluctuated within main periodic bands of 180 yr. We found that the rise and falls of the Guge Kingdom in Ali was synchronic with the fluctuation of land productivity, and the collapse of the Guge Kingdom was obviously related to the sudden change of climate in the 17th century, which turned dry and cold. By combining with historical studies, this study further proposes the mechanism of land productivity fluctuation under climate change on Guge Kingdom. Our findings are helpful to understand the relationship between climate change and social vulnerability, especially providing a typical case study of ancient plateau countries.

Volcanic eruptions, climate changes and their influences on crop harvests and social development are of increasing concern in science communities. Using a dataset of crop harvest scores of southwest China from 1730 to 1910, which was derived from the memorials to the emperors in the Qing Dynasty of China, reconstructed climate proxies and the chronology of large volcanic eruptions occurring between 10°S and 15°N, we analysed possible relationships between crop harvests, climate changes and volcanic eruptions. In addition, some archives of policies and measures related to crops and social development extracted from the chronicles were used to analyse social resilience when faced with poor harvests. The results show that crop harvests in the study area generally increased with fluctuations when there were less low-latitude large volcanic eruptions from 1730 to 1810. However, from 1811 to 1910, volcanoes at low latitudes erupted more frequently, which contributed to concurrent low temperature and drought. Meanwhile, the crop harvests showed a step-down decrease during the following periods of 1810s, 1850s, 1870s and 1890s. Though, the local social system was certainly resilient in facing of such climate and agriculture disasters, i.e. the local society remained stable without significant famine, large-scale migration or social unrest until 1911. The strong resilience of local social systems owed largely to various relieving measures, such as, building barns, exempting or reducing local taxes, allocating farmland to immigrants, and central government dominated grain purchasing and distribution to alleviate disasters.

This study analysed the changes in cropland greenness during 1982–2006 in the North China Plain (NCP) and investigated the warming/cooling effects of the greenness changes. The results show that while spring cropland greenness increased, early summer cropland greenness substantially decreased from 1982 to 2006. In contrast to the cooling and wetting effects of the greenness increase in spring, the greenness reduction in early summer had warming and drying effects. The cooling/warming effects of cropland greenness changes accounted for ∼47% of the spatial variance of daily maximum temperature ( T _max ) change in spring and ∼44% in early summer. The wetting/drying effects of cropland greenness changes accounted for ∼48% of the spatial variance of daily minimum specific humidity (SPH _min ) change in spring and ∼19% in early summer. The cooling–wetting/warming–drying effects mainly resulted from the distinct partitioning of surface net radiation between surface latent heat flux and sensible heat flux over cropland with different greenness. Canopy transpiration plays a dominant role. The increased (decreased) cropland greenness corresponds to high (low) transpiration rate, less (more) sensible heat flux and high (low) humidity, and consequently cooling–wetting (warming–drying) effects. In comparison, there was little change in surface net radiation, although surface albedo and emissivity had changed with greenness change.