Northern Hemisphere Land Temperature Anomaly

I downloaded some monthly temperature data from NOAA today and was able to find a fit to the data for Northern Hemisphere's Land Temperature Anomaly. An anomaly is a deviation from some reference temperature. The fit assumed a parabolic curve and 20 sinusoidal harmonics of a fundamental frequency. The fundamental frequency that gave the best fit had a period of 63.6 years. The fit in the plot below includes the fundamental frequency plus two harmonics. This fit suggests that the temperatures will soon switch to a declining trend if the pattern holds. But there is no guarantee that it will. The fit is what we would expect if the data were cyclical in nature.



(click to enclage)