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Historical documents provide evidence for regional droughts preceding the political turmoil and fall of Beijing in 1644 CE, when more than 20 million people died in northern China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 1624 to 1643 CE in northern China, which coincided with exceptionally cold summers just before the fall of Beijing. Our analysis reveals that these regional hydroclimatic extremes are part of a series of megadroughts along the Pacific Rim, which not only impacted the ecology and society of monsoonal northern China, but likely also exacerbated external geopolitical and economic pressures. This finding is corroborated by last millennium reanalysis data and numerical climate model simulations revealing internally driven Pacific sea surface temperature variations and the predominance of decadal scale La Niña-like conditions to be responsible for precipitation decreases over northern China, as well as extensive monsoon regions in the Americas. These teleconnection patterns provide a mechanistic explanation for reoccurring drought spells during the late Ming Dynasty and the environmental framework fostering the fall of Beijing in 1644 CE, and the subsequent demise of the Ming Dynasty.

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Based on the standard method of dendrochronology, we examined the tree-ring width index of two dominant tree species in the Altay Mountains, China, including Picea obovata and Larix sibirica. We analyzed the basal area increments (BAI) of those two species and the relationships between their radial growth and the climatic factors, which were compared in similar habitats. The results showed that the BAI of P. obovata was greater than L. sibirica, but the radial growth rate of L. sibirica was greater. In recent 60 years, the radial growth of P. obovata negatively correlated with high temperature in the fast growing stage of previous year, while the high temperature in June of current year promoted the radial growth of L. sibirica. There was a significantly negative correlation between radial growth of L. sibirica with temperature in January of current year. The sensitivity of tree growth to climate showed an obvious increase after an abrupt climate change under the background of recent warming and wetting trend in mid-1980s. Results of the moving correlation analysis showed that the response of the radial growth of P. obovata and L. sibirica to temperature and precipitation were enhanced under the background of climate change in the study area.

Precipitation reconstruction for the northwestern Chinese Altay since 1760 indicates the drought signals of the northern part of inner Asia.

Based on the significant positive correlations between the regional tree-ring width chronology and local climate data, the total precipitation of the previous July to the current June was reconstructed since AD 1760 for the northwestern Chinese Altay. The reconstruction model accounts for 40.7 % of the actual precipitation variance during the calibration period from 1959 to 2013. Wet conditions prevailed during the periods 1764-1777, 1784-1791, 1795-1805, 1829-1835, 1838-1846, 1850-1862, 1867-1872, 1907-1916, 1926-1931, 1935-1943, 1956-1961, 1968-1973, 1984-1997, and 2002-2006. Dry episodes occurred during 1760-1763, 1778-1783, 1792-1794, 1806-1828, 1836-1837, 1847-1849, 1863-1866, 1873-1906, 1917-1925, 1932-1934, 1944-1955, 1962-1967, 1974-1983, 1998-2001, and 2007-2012. The spectral analysis of the precipitation reconstruction shows the existence of some cycles (15.3, 4.5, 3.1, 2.7, and 2.1 years). The significant correlations with the gridded precipitation dataset revealed that the precipitation reconstruction represents the precipitation variation for a large area of the northern part of inner Asia. A comparison with the precipitation reconstruction from the southern Chinese Altay shows the high level of confidence for the precipitation reconstruction for the northwestern Chinese Altay. Precipitation variation of the northwestern Chinese Altay is positively correlated with sea surface temperatures in tropical oceans, suggesting a possible linkage of the precipitation variation of the northwestern Chinese Altay to the El Niño-Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). The synoptic climatology analysis reveals that there is the relationship between anomalous atmospheric circulation and extreme climate events in the northwestern Chinese Altay.

May-June maximum temperature reconstruction from mean earlywood density in north central China and its linkages to the summer monsoon activities.

Cores of Pinus tabulaformis from Tianshui were subjected to densitometric analysis to obtain mean earlywood density data. Climate response analysis indicates that May-June maximum temperature is the main factor limiting the mean earlywood density (EWD) of Chinese pine trees in the Shimen Mountains. Based on the EWD chronology, we have reconstructed May-June maximum temperature 1666 to 2008 for Tianshui, north central China. The reconstruction explains 40.1% of the actual temperature variance during the common period 1953-2008. The temperature reconstruction is representative of temperature conditions over a large area to the southeast and northwest of the sampling site. Preliminary analysis of links between large-scale climatic variation and the temperature reconstruction shows that there is a relationship between extremes in spring temperature and anomalous atmospheric circulation in the region. It is thus revealed that the mean earlywood density chronology of Pinus tabulaformis has enough potential to reconstruct the temperature variability further into the past.

Tree-ring-based reconstruction of precipitation in the Changling Mountains, China, since A.D.1691.

Seven different tree-ring parameters were obtained from Chinese pine (Pinus tabulaeformis) in the Changling Mountains, China. The chronologies were analyzed individually and then compared with each other. The climate response analysis shows that total precipitation (September-July) is the main factor limiting the radial growth of Chinese pine in the Changling Mountains. Thus, the residual earlywood width chronology was used to estimate precipitation (September-July) for the period AD 1691-2006, and explained 46.9% of the precipitation variance. Drought events in our reconstruction are compared to historical archives for Gansu and north-central China. The results reveal the climatic extremes over much of Gansu. Some events have had profound impacts on the Gansu people over the past several centuries. Spatial analysis shows that the precipitation reconstruction has strong common signals for North-central China. The reconstructed series is correlated significantly with Helan Mountains Palmer drought severity index (PDSI), as well as with previous results from Jiuquan, Shandan, Huashan, Luya Mountains, and even the state of Mongolia. Our results suggest that some dry periods are coincident with solar minima over the past several hundred years. Multitaper spectral analysis reveals the existence of significant 24.4-year, 12.2-year, and 2.4- to 3.4-year periods of variability.