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A dangerous trend
How anthropogenic climate change affects heat waves and drought is one of the most important environmental issues facing societies around the world. Zhang et al. exhibit a 260-year record of soil temperature and moisture over the interior of East Asia that reveals a sharp change to warmer and drier conditions (see Zhang and Fang’s perspective). The extreme episodes of hotter and drier climates over the past 20 years, which are unprecedented in previous 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
Abstract
Unprecedented competition from heat waves and drought over the past two decades has been reported in the interior of East Asia. Reconstructions from heat wave rings and soil moisture over the past 260 years reveal a sharp shift to a warmer and drier climate in this region. Improved earth-atmosphere coupling, coupled with a persistent soil moisture deficit, appears to intensify surface warming and anticyclonic circulation anomalies, fueling heat waves that worsen soil drying. Our analysis demonstrates that the magnitude of the hot and dry anomalies that have worsened over the past two decades is unprecedented over the past quarter of a millennium, and this trend clearly exceeds the range of natural variability. The “hockey stick” type shift warns that warming and drying out is potentially irreversible beyond a tipping point in the East Asian climate system.
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