To meet the low warming targets proposed in the 2015 Paris Agreement, substantial reduction in carbon emissions is needed in the future. It is important to know how surface climates respond under low warming targets. The present study investigates the surface temperature changes under the low-forcing scenario of Representative Concentration Pathways (RCP2.6) and its updated version (Shared Socioeconomic Pathways, SSP1-2.6) by the Flexible Global Ocean-Atmosphere-Land System (FGOALS) models participating in phases 5 and 6 of the Coupled Model Intercomparison Project (CMIP5 and CMIP6, respectively). In both scenarios, radiative forcing (RF) first increases to a peak of 3 W m−2 around 2045 and then decreases to 2.6 W m−2 by 2100. Global mean surface air temperature rises in all FGOALS models when RF increases (RF increasing stage) and declines or holds nearly constant when RF decreases (RF decreasing stage). The surface temperature change is distinct in its sign and magnitude between the RF increasing and decreasing stages over the land, Arctic, North Atlantic subpolar region, and Southern Ocean. Besides, the regional surface temperature change pattern displays pronounced model-to-model spread during both the RF increasing and decreasing stages, mainly due to large intermodel differences in climatological surface temperature, ice-albedo feedback, natural variability, and Atlantic Meridional Overturning Circulation change. The pattern of tropical precipitation change is generally anchored by the spatial variations of relative surface temperature change (deviations from the tropical mean value) in the FGOALS models. Moreover, the projected changes in the updated FGOALS models are closer to the multi-model ensemble mean results than their predecessors, suggesting that there are noticeable improvements in the future projections of FGOALS models from CMIP5 to CMIP6.

中文翻译：

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CMIP5 和 CMIP6 低变暖情景下 FGOALS 模型预测的地表温度变化

为了实现 2015 年巴黎协定提出的低变暖目标，未来需要大幅减少碳排放。了解在低变暖目标下地表气候如何响应非常重要。本研究通过灵活的全球海洋 - 大气 - 陆地系统（FGOALS）模型研究了代表性浓度路径（RCP2.6）及其更新版本（共享社会经济路径，SSP1-2.6）的低强迫情景下的地表温度变化参与耦合模型比对项目（分别为 CMIP5 和 CMIP6）的第 5 和第 6 阶段。在这两种情况下，辐射强迫 (RF) 在 2045 年左右首先增加到 3 W m-2 的峰值，然后在 2100 年减少到 2.6 W m-2。在所有 FGOALS 模型中，当 RF 增加（RF 增加阶段）时，全球平均地表气温升高，当 RF 减少（RF 减少阶段）时，全球平均地表气温下降或几乎保持不变。在陆地、北极、北大西洋次极地地区和南大洋的 RF 增加和减少阶段之间，地表温度变化的符号和幅度是不同的。此外，区域地表温度变化模式在 RF 增加和减少阶段都显示出明显的模型间扩展，主要是由于气候表面温度、冰-反照率反馈、自然变率和大西洋经向翻转环流变化的较大模型间差异. 在 FGOALS 模型中，热带降水变化的模式通常取决于相对地表温度变化（与热带平均值的偏差）的空间变化。此外，更新后的 FGOALS 模型中的预测变化比它们的前辈更接近多模型集合平均结果，这表明 FGOALS 模型从 CMIP5 到 CMIP6 的未来预测有明显的改进。