Tests of Periodic and Quasi-periodic Fluctuations in Paleoclimate Data Sets

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Abstract

Embedded in various events on Earth are proxy data that allow us to map the temperature of the Earth over many years. In this work the temperature fluctuations for a number of proxy data sets were analyzed to express any periodic and quasi-periodic fluctuations in the data sets. The changing patterns in tree ring growth and temperature fluctuations in Greenland ice core samples, along with other data, were tested with a goal to understanding periodic and quasi-periodic patterns in paleoclimate variability. Some quasi-periodic signatures have been identified that predate the Industrial Revolution, during much of which direct data on temperature are not available. Earth temperature appears to have a number of periodic and quasi-periodic intervals that indicate both global warming and global cooling cycles. From comparisons of temperature proxy data for varying time periods a number of “quasi-cycles” have been identified that appear to be periodic while being frequency modulated. The well-known sunspot cycle of eleven years persists in all of the proxies studied that had data spanning a decade or less. In addition, long-term time intervals show both cycles extending from about 600 years to 500,000 years during which the temperature increased and decreased in a quasi-periodic way. From a study of the long-term changes, a base can be established upon which recent green-house gas effects on temperature can be impressed.