Pre-Industrial (1750–1850 CE) Cold Season Warmth in Northeastern China

Contrary to global warming projections, northern mid-latitude continents have suffered from an increased frequency of unusually cold winters during the last few decades. However, a lack of longer-term cold-season temperature records from mid-latitudes hampers our understanding of the forcing mechanisms of this temperature variability. Here we report a Group 1 alkenone-based high-resolution record of cold-season temperatures extending to the pre-industrial era (since 1700 CE) from Lake Luming in northeastern China. By comparing with the instrumental and historical records in the region, we verify the high efficacy of Group 1 alkenones as recorders of cold-season temperature variability. Our record shows pre-industrial warmth between 1750 and 1850 CE relative to anthropogenic industrial period (since 1850 CE), which is largely driven by variability of the Arctic Oscillation, with a negligible contribution from anthropogenic greenhouse-gas forcing. Our results highlight the importance of internal atmospheric circulation in driving cold-season temperatures in northeastern China.