A dangerous trend: How anthropogenically driven climate change is affecting heat waves and drought is one of the most important environmental issues facing societies around the globe. Zhang et al. present a 260-year-long record of temperature and soil moisture over inner East Asia that reveals an abrupt shift to hotter and drier conditions (see the Perspective by Zhang and Fang). Extreme episodes of hotter and drier climate over the past 20 years, which are unprecedented in the earlier records, are caused by a positive feedback loop between soil moisture deficits and surface warming and potentially represent the start of an irreversible trend. Science , this issue p. 1095 ; see also p. 1037

China is a key region for understanding fire activity and the drivers of its variability under strict fire suppression policies. Here, we present a detailed fire occurrence dataset for China, the Wildfire Atlas of China (WFAC; 2005–2018), based on continuous monitoring from multiple satellites and calibrated against field observations. We find that wildfires across China mostly occur in the winter season from January to April and those fire occurrences generally show a decreasing trend after reaching a peak in 2007. Most wildfires (84%) occur in subtropical China, with two distinct clusters in its southwestern and southeastern parts. In southeastern China, wildfires are mainly promoted by low precipitation and high diurnal temperature ranges, the combination of which dries out plant tissue and fuel. In southwestern China, wildfires are mainly promoted by warm conditions that enhance evaporation from litter and dormant plant tissues. We further find a fire occurrence dipole between southwestern and southeastern China that is modulated by the El Niño-Southern Oscillation (ENSO).

We have reconstructed the Palmer Drought Severity Index (PDSI) from 1618 to 2005 for the Guiqing Mountain area, north central China, using tree rings of Pinus tabulaeformis. The reconstruction explains 49% of the actual PDSI variance during the common period 1951–2005. The PDSI reconstruction is representative of moisture conditions over a large area to the south and east of the sampling site, the core area for the 1997 severe drought. It shows slightly different variations when compared to other available PDSI reconstructions north and west of the sampling sites. The drought epoch since 1994 is most severe for our study region, with least intensity for the Helan Mountain area. The drought in 1997 was centered in the Guiqing Mountain area, and appears to be the most extreme drought event over the length of reconstruction. Significant spectral peaks are identified at 2.1, 2.3, 2.5, 3.2, 3.6, 42.7 and 53.8 years. Our reconstructed droughts are significantly correlated with sea surface temperature in the northern Indian Ocean, western equatorial Pacific Ocean, eastern equatorial Pacific Ocean, Eastern China Sea and Sea of Japan. The linkages to the Indian and Pacific Oceans suggest the connection of regional moisture variations to the Asian monsoon circulations. Copyright © 2009 Royal Meteorological Society

Drought reconstruction from 1794 to 2003 in the eastern part of NW China was devel- oped by calibrating tree rings of Picea wilsonii on Xinglong Mountain with the Palmer drought sever- ity index (PDSI). The reconstruction explains 40% of the actual PDSI variance during the period from 1951 to 2003. The most significant drought period over the reconstructed time span occurred during the 1920s to 1930s. The drought reconstructions show a climate transition in 1921 on a decadal scale and significant cyclic patterns that were identified in intervals of 10.5, 7.9-8.3, ~3.5, 3.0-3.2, 2.7-2.8 and ~2 yr. This reconstruction is representative of regional drought patterns in eastern NW China and demonstrates that they are different from patterns in western NW China.