One of the most hotly debated questions about modern global warming (roughly 1960–present) is how much credit (or blame) for it goes to the Sun, and how much to increased carbon dioxide in the atmosphere. The U.N Intergovernmental Panel on Climate Change and “mainstream” climate scientists tend to discount the former and pin all or almost all on the latter. The Nongovernmental International Panel on Climate Change tends to discount the latter and pin all or almost all on the former.
Studies pro and con appear from time to time. The most recent is “Harmonic Analysis of Worldwide Temperature Proxies for 2000 Years,” by Horst-Joachim Lüdecke, of the University of Applied Sciences, Saarbrücken, Germany, and Carl-Otto Weiss, of the Center for Research and Advanced Studies of the National Polytechnic Institute.
The gist: A complex analysis of two millennia of local and regional temperature data from around the globe indicates that temperature rises and falls in cycles of roughly 1,000, 460, and 190 years, and when those cycles coincide, we get the markedly warmer (Roman, ~0 AD; Medieval, and Present, ~1980–present) or cooler (particularly, the Little Ice Age, ~1500) periods.
Further, as Pierre Gosselin notes in his blog post about the study, “the sum of the three cycles shows the temperature increase from 1850 to 1995 as a result of the three natural cycles,” from which the authors infer that “CO2 plays only a minor role (if any) for the global climate.”
Gosselin concludes his post:
Lüdecke and Weiss note that the present maximum of the cycle sum corresponds well with the world temperature stagnation since 1995 AD, the stagnation unexplained by current climate models. As the dominant cycles have persisted for an extended time, one can assume that they will persist for the near future. They write: “This allows to predict cooling until 2070 AD.” [Emphasis Gosselin’s.]
This study adds new evidence for the thesis of S. Fred Singer and Dennis T. Avery’s book Unstoppable Global Warming: Every 1500 Years.