南京大学杨保教授团队近日取得一项新成果。他们报道了代用物选择对公元纪年年代全球年平均温度重建的影响。2024年7月3日出版的《中国科学：地球科学》发表了这项成果。

本研究采用了一种广泛使用合成-加-尺度的方法来阐明代用物记录的选择对温度重建的影响。为了保证数据的统一性，研究使用了来自PAGES 2k代理网络跨越过去约2000年的不同类型的代用物记录，以调查在过去两千年期间和全球温度重建中代用物选择的潜在影响。在此基础上，研究了年气温的长期变化趋势、光谱特征和火山响应。

结果揭示在1-1850CE期间，全球年平均气温在使用树木年轮和非树木年轮记录中都有明显的变冷趋势，南半球(SH)的变冷趋势强于北半球(NH)。然而，长期趋势因代用物记录的不同组合而有所不同。基于不同类型代用物的不同重建在火山响应和光谱性质方面也表现出不同的特征。

基于树木年轮的温度重建对热带火山喷发的冷却响应较强，而非基于树木年轮的温度重建对热带火山喷发的冷却响应较弱，这可能与代用物的年代不确定和低时间分辨率有关。树轮宽度记录倾向于保留大部分的高频(＜200年)变率，而非树轮代用物倾向于捕获更大比例的低频(＞200年)变率。目前的代用网络时空覆盖不足，特别是第一个千年以及北半球和热带地区的代用网络时空覆盖不足，因此需要努力减少与当前代理网络的时空覆盖不足相关的公元纪年年代温度重建的不确定性，还需要开发统计方法，提高信号强度并限制现有代用物记录中的不确定性。

研究人员表示，PAGES 2k联合体在2019年重建的全球年平均温度代表了公元纪年年代全球气候变率最具影响力的序列之一。然而，重建方法的选择和不同地区不同时间分辨率的代用物记录的选择，对重建结果的影响尚不清楚。

附：英文原文

Title: The influence of proxy selection on global annual mean temperature reconstructions during the Common Era

Author: Bao YANG, Xia LI, Minhui HE, Feng WANG, Yesi ZHAO, Peng ZHANG, Jianglin WANG

Issue&Volume: 2024/07/03

Abstract: The reconstruction of global annual mean temperatures made by the PAGES 2k Consortium in 2019 represents one of the most influential sequences of global climate variability over the Common Era. However, it is still not clear how the reconstruction can be influenced by the selection of reconstruction methods and the selection of proxy records with different temporal resolutions over different regions. We adopt a widely used Composite-Plus-Scale method to elucidate the effects of the selection of the proxy records on temperature reconstruction. To ensure the uniformity of data, different types of proxy records spanning the past ~2000years from the PAGES 2k proxy network were used to investigate the potential effects of proxy selection in hemispheric and global temperature reconstructions during the past two millennia. The long-term trends, spectral characteristics, and volcanic responses of the annual temperatures were studied based on the reconstructions. Our results reveal a significant cooling trend in the global annual mean temperature using both tree-ring and non-tree-ring records during the 1–1850 CE period, and show that the cooling exhibits a stronger trend in the Southern Hemisphere (SH) than that in the Northern Hemisphere (NH). Yet, the long-term trends vary according to different combinations of proxy records. Different reconstructions based on different types of proxies also exhibit different features in terms of volcanic responses and spectral properties. Tree-ring-based temperature reconstructions show stronger cooling responses to tropical volcanic eruptions, while non-tree-ring-based reconstructions suggest less robust volcanic responses, which may be related to dating uncertainties and low temporal resolution of the proxies. Tree-ring width records tend to preserve a substantial proportion of high-frequency (<200years) variability, whereas non-tree-ring proxies tend to capture a larger fraction of low-frequency (>200years) variations. Efforts are needed to reduce uncertainties of the temperature reconstruction over the Common Era associated with the insufficient spatiotemporal coverage of the current proxy network, especially for the first millennium and for the SH and tropics, also to develop statistical methods and to improve the signal strength and constrain uncertainties in existing proxy records.

DOI: 10.1007/s11430-024-1348-3

Source: https://www.sciengine.com/SCES/doi/10.1007/s11430-024-1348-3