The Last Interglacial (LIG, 129–116 thousand years ago) is an excellent case study for global warming scenarios and a target for proxy-model comparisons. The LIG global average sea surface temperature (SST) was ~0.5 °C higher than pre-industrial (PI). Contrary to the global average, tropical SST proxy compilations and model simulations show a negative anomaly in LIG SST relative to PI. Here, we present a LIG SST record from marine sediment core GL-1180 retrieved from the western tropical South Atlantic (WTSA). The SST record is based on Mg/Ca ratios of planktonic foraminifera Globigerinoides ruber (white). Our results indicate a warmer LIG in the WTSA relative to PI and Holocene conditions. We show that a positive LIG SST anomaly in tropical regions can be explained by polar sea ice loss during the LIG, which warms the ocean surface all the way into the tropics. The disagreement between proxy results and model simulations from the fourth phase of the Paleoclimate Modelling Intercomparison Project could result from uncertainties in our proxy for SST and/or limitations of numeric models in capturing transient forcings and feedbacks in Earth's climate system and imprecise boundary conditions. Additional studies are warranted to better constrain the LIG SST evolution in tropical regions.

末次间冰期（LIG，129-116000 年前）是全球变暖情景的优秀案例研究，也是代理模型比较的目标。LIG 全球平均海面温度 (SST) 比工业化前 (PI) 高约 0.5 °C。与全球平均水平相反，热带 SST 代理汇编和模型模拟显示 LIG SST 相对于 PI 存在负异常。在这里，我们展示了从西热带南大西洋 (WTSA) 检索到的海洋沉积物核心 GL-1180 的 LIG SST 记录。SST 记录基于浮游有孔虫Globigerinoides ruber的 Mg/Ca 比率（白色的）。我们的结果表明，相对于 PI 和全新世条件，WTSA 中的 LIG 温度更高。我们表明，热带地区的 LIG SST 正异常可以用 LIG 期间的极地海冰损失来解释，这使海洋表面一直变暖到热带。古气候建模比对项目第四阶段的代理结果和模型模拟之间的分歧可能是由于我们的 SST 代理的不确定性和/或数值模型在捕捉地球气候系统中瞬态强迫和反馈方面的局限性以及不精确的边界条件。有必要进行进一步的研究以更好地限制热带地区的 LIG SST 演变。