Van Geel, B., Raspopov, O.M., Renssen, H., van der Plicht, J., Dergachev, V.A. and Meijer, H.A.J. 1999. The role of solar forcing upon climate change. Quaternary Science Reviews 18: 331-338.
What was done
The authors review what is known about the relationship between variations in the abundances of the cosmogenic isotopes 14C and 10Be and millennial-scale climate oscillations during the Holocene and portions of the last great ice age.
What was learned
The authors show that "there is mounting evidence suggesting that the variation in solar activity is a cause for millennial scale climate change," which is known to operate independently of the glacial-interglacial cycles that are forced by variations in the Earth's orbit about the Sun. They also review the evidence for two potential mechanisms by which the postulated solar-climate connection may be implemented, making a strong case for the validity of one or both of them.
What it means
In the words of the authors, "accepting the idea of solar forcing of Holocene and Glacial climatic shifts has major implications for our view of present and future climate." It implies, as they note, that "the climate system is far more sensitive to small variations in solar activity than generally believed" and that "it could mean that the global temperature fluctuations during the last decades are partly, or completely explained by small changes in solar radiation." These observations, of course, call into question the conventional wisdom of attributing the global warming of the past century or so to the ongoing rise in the air's CO2 content. It could well be that we have the sun to thank for rescuing us from the cold and unfriendly grip of the recently-departed Little Ice Age.
Reviewed 1 January 2000