Andean glaciers have been shrinking due to long-term climatic warming during the past 100 years. Stuart-Smith et al. (2021) used observations and numerical models to evaluate the anthropogenic contribution to the centennial retreat of the Palcaraju Glacier in the Peruvian Cordillera Blanca. According to their central estimate, the glacier retreat is thought to be entirely the result of the observed 1 °C warming since 1880 in this region, of which they consider 85–105% as human-induced warming. However, this attribution must be questioned because the numerical models used by the authors fail to replicate the well-documented Andean temperature and glacier history of the Common Era. In a recent literature synthesis we have demonstrated that Andean glaciers retreated significantly during the Medieval Climate Anomaly (MCA, 1000–1200 CE) when the vast majority of all South American land sites experienced a warm phase, recorded as a near-global natural event, that is not linked with human activity (Lüning et al., 2019a). The MCA was followed by the Little Ice Age (LIA, 1300–1850 CE) when many Andean glaciers advanced significantly, some of them even reaching their maximum Holocene down-valley extension. In contrast, the “hindcast” of Stuart-Smith et al. (2021) erroneously suggests hardly any glacier length fluctuations for pre-industrial times. Given the unsuccessful “hindcast”, we do not consider the attribution results of the study as robust.

由于过去 100 年的长期气候变暖，安第斯冰川一直在缩小。斯图尔特-史密斯等人。（2021 年）使用观测和数值模型来评估人为对秘鲁科迪勒拉布兰卡地区帕卡拉茹冰川百年退缩的贡献。根据他们的中央估计，冰川退缩被认为完全是自 1880 年以来在该地区观察到的 1°C 变暖的结果，他们认为其中 85-105% 是人为引起的变暖。然而，这种归因必须受到质疑，因为作者使用的数值模型未能复制有据可查的安第斯温度和共同时代冰川的历史。在最近的文献综合中，我们已经证明安第斯冰川在中世纪气候异常（MCA，公元 1000-1200 年）期间显着退缩，当时绝大多数南美陆地地点都经历了温暖阶段，记录为近乎全球的自然事件，这与人类活动无关（Lüning 等人，2019a）。MCA之后是小冰河时代（LIA，公元 1300-1850 年）当许多安第斯冰川显着推进时，其中一些甚至达到了全新世最大的谷底延伸。相比之下，Stuart-Smith 等人的“后预测”。(2021) 错误地表明前工业时代几乎没有任何冰川长度波动。鉴于不成功的“后预测”，我们认为该研究的归因结果并不可靠。