| Summary: | The historical global surface temperature (GST) exhibits staircase-like evolutions with both accelerated warming periods and warming slowdown periods. The rate of GST change slowed down during 2003-2012, relative to the warming acceleration in the late 20th century and is termed as the global warming slowdown period. Since 1850, other global warming slowdown periods have also been identified. The proposed explanations for this warming slowdown can be understood as whether it is caused by the external forcing (e.g. the increased volcano activities, the increased aerosols and decreased water vapor concentration) or it is due to the internal variability from the Pacific Ocean, the Indian Ocean, or the Atlantic Ocean. This study reviews the observed historical records, previous analysis, and offers interpretations of coupled climate model experiments, reconciles the proposed mechanisms and quantifies their relevant contributions to the GST evolution. ☐ The first section of this study focuses on the surface signal, the evolution of GST, and the main drivers for the GST change in different time scales. In this section, the Ensemble Empirical Mode Decomposition (EEMD) method is applied to the observed GST time series for the period of 1850-2020, which is decomposed into a group of signals respectively on inter-annual (< 8 years), inter-decadal (9-20 years) and multi-decadal (60-80 years) timescales as well as a non-linear secular trend. Both the inter-annual and inter-decadal signals in GST can be linked to the El Niño-Southern Oscillation (ENSO)-like variability in the Pacific Ocean. In contrast, the multi-decadal signal in GST is in phase with the Atlantic Multi-decadal Oscillation (AMO) and the associated sea surface temperature (SST) patterns resemble the AMO in the North Atlantic and its trans-basin footprints in the other oceans. In order to assess the respective roles of the Pacific, the Atlantic, and the external forcing in driving the GST change in historical records, a suit of Pacemaker experiments has ...
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