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IN addition to the well-known warming of ∼0.5 °C since the middle of the nineteenth century, global-mean surface temperature records^1–4display substantial variability on timescales of a century or less. Accurate prediction of future temperature change requires an understanding of the causes of this variability; possibilities include external factors, such as increasing greenhouse-gas concentrations^5–7 and anthropogenic sulphate aerosols^8–10, and internal factors, both predictable (such as El Niño¹¹) and unpredictable (noise^12,13). Here we apply singular spectrum analysis^14–20 to four global-mean temperature records^1–4, and identify a temperature oscillation with a period of 65–70 years. Singular spectrum analysis of the surface temperature records for 11 geographical regions shows that the 65–70-year oscillation is the statistical result of 50–88-year oscillations for the North Atlantic Ocean and its bounding …