20th Century Global Temps Likely Within Natural Variation

UN IPCC Lead Author Philip J. Lloyd published the results of a new study in Energy & Environment Vol. 26, No. 3 (May 2015) in which he concludes that “while some portion of the temperature change observed in the 20th century was probably caused by greenhouse gases, there is a strong likelihood that the major portion was due to natural variations.” His analysis of natural centennial variations in the global temperature during the Holocene period (approximately the last 11,700 years) using data from the National Climatic Data Center determined that:

“The best estimate of the centennial standard deviation of temperature during the Holocene is 0.98 ± 0.27 o C.

During the 20th century, thermometers recorded an increase of about 0.7º C. It seems reasonably certain that there was some warming due to the increasing buildup of greenhouse gases in the atmosphere, but it seems difficult to estimate the magnitude of this warming in the face of a likely natural variation of the order of 1º C. The signal of anthropogenic global warming may not yet have emerged from the natural background.”

Standard Deviations in Holocene temperature anomaly for Greenland Ice Sheet (GISP) data by oxygen isotope

Screen Shot 2016-01-04 at 12.15.56 PM

This important finding stands in stark contrast to the strongly worded and widely promoted conclusion of the IPCC in AR5: “It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.”

In addition to his former role as IPCC lead author, Lloyd is a South African Nuclear Physicist who has authored more than 150 refereed publications.


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