Projected Late 21st Century Warming Unprecedented in Northwest China in a Holocene Context

Northwest China is facing socio-environmental challenges linked to ongoing climatic warming. However, a scarcity of regional paleorecord syntheses limits our understanding of natural long-term climate variability in the region and hinders the contextualization of contemporary warming. Here, we present paleorecord syntheses for both summer and annual temperatures during the Holocene based on a range of lacustrine sediment records from northwest China, with consideration of chronological uncertainties within records. The syntheses show similar summer and annual temperature variations, including peak warmth at ∼9000 years BP, followed by a 2000-year cooling trend, and stable temperatures thereafter. These variations may reflect inter-seasonal impact of summer insolation forcing through climate feedbacks (e.g., Arctic sea-ice cover) that are still not well represented in climate models. The early-Holocene peak warmth was >1.0°C warmer than the 20th century mean warmth, but is expected to be exceeded during the 21st century even under a low emission scenario.