"There is little need to ascribe a unique cause to late 20th-century global warming (such as elevated atmospheric CO2 concentrations), as this latest warming is merely a run-of-the-mill relative warming, sitting atop a solar-induced baseline warming that has been in progress for the past four centuries."
"In considering Qian and Lu's findings, it is important to note that, once again, no help from greenhouse gas emissions was needed to reconstruct the past thousand-year history of Earth's global mean temperature; it was sufficient to merely employ known oscillations in solar radiation variability. And as for the future, the two authors predict that "global-mean temperature will decline to a renewed cooling period in the 2030s, and then rise to a new high-temperature period in the 2060s." Given the cessation in warming observed in the surface and lower tropospheric temperature records over the past decade, it appears their prediction is well on its way to being validated.
Clearly, there is much to recommend the overriding concept that is suggested by the data of these several papers, i.e., that the Sun rules the Earth when it comes to orchestrating major changes in the planet's climate. It is becoming ever more clear that the millennial-scale oscillation of climate that has reverberated throughout the Holocene is indeed the result of similar-scale oscillations in some aspect of solar activity. Consequently, as Mayewski et al. (2004) suggested a decade ago, "significantly more research into the potential role of solar variability is warranted, involving new assessments of potential transmission mechanisms to induce climate change and potential enhancement of natural feedbacks that may amplify the relatively weak forcing related to fluctuations in solar output." We only hope that more scientists will take note and examine the intriguing relations between our nearest star and our planet's temperature."
[Illustrations, footnotes and references available in PDF version]
The claim that anthropogenic greenhouse gas emissions have been responsible for the warming detected in the twentieth century is based on what Loehle (2004) calls "the standard assumption in climate research, including the IPCC reports," that "over a century time interval there is not likely to be any recognizable trend to global temperatures (Risbey et al., 2000), and thus the null model for climate signal detection is a flat temperature trend with some autocorrelated noise," so that "any warming trends in excess of that expected from normal climatic variability are then assumed to be due to anthropogenic effects." If, however, there are significant underlying climate trends or cycles-or both-either known or unknown, that assumption is clearly invalid.