The decadal-scale global-mean surface temperature (GMST) trend fluctuates between rapid-warming, slow-warming and cooling under the combined action of external forcing (EX) and internal variability. However, the principal contributors to the time-varying trends of GMST across decadal scales in current and future climates remain elusive. Here, by leveraging observations and initial-condition large ensembles, we unravel that historical GMST trend fluctuations are predominantly driven by EX on timescales exceeding ∼9 years within the current climate, with anthropogenic and volcanic aerosols being the primary drivers. However, in the warming climate, the significant contribution of EX on decadal scales is projected to decrease. This is primarily due to anthropogenic aerosol mitigation efforts and the absence of unpredictable volcanism. Despite the continuous increase in greenhouse gases, these factors are expected to delay the emergence of EX-dominance to ∼14-year timescale. Our results quantitatively underscore the pivotal role of the EX in modulating GMST trend fluctuations and its potential weakening at decadal scales in the warming climate, indicating that predicting near-term changes in GMST may become less certain in the future.

中文翻译：

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当前和未来气候下外强迫对全球平均地表温度时变趋势的作用

在外部强迫（EX）和内部变率的共同作用下，十年尺度的全球平均地表温度（GMST）趋势在快速变暖、缓慢变暖和变冷之间波动。然而，在当前和未来气候下，跨十年尺度 GMST 时变趋势的主要贡献者仍然难以捉摸。在这里，通过利用观测和初始条件大型集合，我们揭示了历史 GMST 趋势波动主要由 EX 在当前气候下超过 9 年的时间尺度上驱动，其中人为和火山气溶胶是主要驱动因素。然而，在气候变暖的情况下，EX 在十年尺度上的显着贡献预计会减少。这主要是由于人为气溶胶缓解措施以及缺乏不可预测的火山活动。尽管温室气体持续增加，但这些因素预计会将 EX 主导地位的出现推迟至约 14 年的时间尺度。我们的结果定量地强调了 EX 在调节 GMST 趋势波动中的关键作用及其在气候变暖的十年尺度上的潜在减弱，这表明预测 GMST 的近期变化在未来可能变得不太确定。