Global surface temperature has been increasing since the beginning of the 20th century but with a highly variable warming rate, and the alternation of rapid warming periods with ‘hiatus’ decades is a constant throughout the series. The superimposition of a secular warming trend with natural multidecadal variability is the most accepted explanation for such a pattern. Since the start of the 21st century, the surface global mean temperature has not risen at the same rate as the top-of-atmosphere radiative energy input or greenhouse gas emissions, provoking scientific and social interest in determining the causes of this apparent discrepancy. Multidecadal natural variability is the most commonly proposed cause for the present hiatus period. Here, we analyze the HadCRUT4 surface temperature database with spectral techniques to separate a multidecadal oscillation (MDV) from a secular trend (ST). Both signals combined account for nearly 88% of the total variability of the temperature series showing the main acceleration/deceleration periods already described elsewhere. Three stalling periods with very little warming could be found within the series, from 1878 to 1907, from 1945 to 1969 and from 2001 to the end of the series, all of them coincided with a cooling phase of the MDV. Henceforth, MDV seems to be the main cause of the different hiatus periods shown by the global surface temperature records. However, and contrary to the two previous events, during the current hiatus period, the ST shows a strong fluctuation on the warming rate, with a large acceleration (0.0085°C year−1 to 0.017°C year−1) during 1992–2001 and a sharp deceleration (0.017°C year−1 to 0.003°C year−1) from 2002 onwards. This is the first time in the observational record that the ST shows such variability, so determining the causes and consequences of this change of behavior needs to be addressed by the scientific community.
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机译：自20世纪初以来，全球地表温度一直在升高，但升温速率变化很大，整个系列中恒定的快速升温周期与“休止期”十年交替出现。长期变暖趋势与自然年代际变化的叠加是这种模式最被接受的解释。自21世纪初以来，地表全球平均温度并未以与大气层顶部辐射能输入或温室气体排放相同的速度上升，这激发了科学和社会兴趣来确定这种明显差异的原因。在当前的休止期，多年代际自然变异是最普遍提出的原因。在这里，我们使用光谱技术分析了HadCRUT4表面温度数据库，以将多十年振荡（MDV）与长期趋势（ST）分开。这两个信号的总和占温度序列总变化的近88％，显示了其他地方已经描述的主要加速/减速周期。从1878年到1907年，从1945年到1969年以及从2001年到该系列的末期，在该系列中可以找到三个停滞期，几乎没有变暖，所有这些都与MDV的冷却阶段相吻合。今后，MDV似乎是全球表面温度记录显示的不同休止期的主要原因。但是，与之前的两个事件相反，在当前的中断时间段内，ST的升温速率波动很大，加速度较大（0.0085°C年 -1 到0.017°C年） −1 ）在1992-2001年期间，并从2002年开始急剧减速（0.017°C year -1 至0.003°C year -1 ） 。这是观测记录中ST首次显示出这种可变性，因此确定行为改变的原因和后果需要科学界解决。
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