Comment on cp-2022-92

Abstract

Global climate has undergone dramatic changes over the past 200 years, accurately identifying the climate transition and its controlling factors will help to address the risks posed by global warming and predict future climate trends. To clarify climate change over the past 200 years, detailed analyses of chronology, grain size, color reflectance (L*, a*) and carbon content (TOC, TIC) were conducted on a 200-year high resolution (~ 2 a) sedimentary record from lake Ebinur in Xinjiang, northwest China. The results show that the median grain size (Md) of lake sediments ranges from 5.5 μm to 9.9 μm, with a mean value of 7.0 μm. Multi-parameter analysis of grain size suggests that the sediments in lake Ebinur are mainly transported by wind, and there are two kinds of different sources and transport processes: the fine-grained sediments (< 20 μm) are background dust that was transported by long distance high-altitude suspension, while the coarse-grained sediments (> 20 μm) are local and regional dusts that were transported from short distances at low altitudes. Comparative analysis of multi-proxies including grain size、color reflectance and carbon content reveals that 1920 AD is the time point of climate transition in the past 200 years. In the early period (1816–1876 AD), the high C values indicate strong transport dynamics; the high proportion of ultrafine component indicates strong pedogenesis, combined with high organic carbon content and high a* values, it is inferred that the water vapor content is relatively higher. Overall, this period corresponds to the cold and wet climate. In the later period (1920–2019 AD), the proxies show opposite changes, which may reveal a warm and dry climate. Based on a comprehensive analysis of multiple drivers (i.e., solar radiation, greenhouse gases and volcanic eruption), we propose that the increase of solar irradiance in 1920 AD played a dominant role in the Asian climate transition, and that the gradual rise in the concentrations of greenhouse gases (CO2 and CH4) may have a positive feedback effect on the climate transition.