Volume 11, Number 35: 27 August 2008
In the March 2008 issue of Physics Today, Scafetta and West (2008) describe their quest to identify a solar signal in earth's global temperature record. They begin by noting that the most recent IPCC report concludes that "the contribution of solar variability to global warming is negligible, to a certainty of 95%," which would appear to heavily stack the deck against them in terms of their being successful. However, they note that whereas "the statistical variability in earth's average temperature is interpreted as noise" by most climate modelers and "thought to contain no useful information," they believe that "the variations in earth's temperature are not noise, but contain substantial information about the source of variability," which they suggest is total solar irradiance or TSI.
With this outlook on the subject, the two researchers further suggest that "variations in TSI are indicative of the sun's turbulent dynamics," as represented by "changes in the number, duration, and intensity of solar flares and sunspots, and by the intermittency in the time intervals between dark spots and bright faculae," which variability has the capacity to "move the global temperature up and down for tens or even hundreds of years." But, as the saying goes, talk is cheap. So where's the evidence for this belief?
Scafetta and West proceed to indicate that "both the fluctuations in TSI, using the solar flare time series as a surrogate, and earth's average temperature time series are observed to have inverse power-law statistical distributions," and that the inverse power-law index "turns out to be the same for both the solar flare and temperature anomaly time series," citing the work of Scafetta and West (2003), which suggests, in their words, that "the statistics of the temperature anomalies inherit the statistical structure that was evident in the intermittency of the solar flare data."
The two researchers thus conclude that "the sun is influencing climate significantly more than the IPCC report claims," and that "the current anthropogenic contribution to global warming is significantly over-estimated." In fact, citing Scafetta and West (2007), they go on to say they "estimate that the sun could account for as much as 69% of the increase in earth's average temperature, depending on the TSI reconstruction used."
Clearly, and in light of Scafetta and West's intriguing findings over the years, as well as those of many other scientists (see Climate Change (Forcing Factors - Solar) in our Subject Index), it behooves everyone to keep an open mind on the subject as pertinent research continues to be conducted.
Sherwood, Keith and Craig Idso
Scafetta, N. and West, B.J. 2003. Solar flare intermittency in the Earth temperature anomalies. Physical Review Letters 90: 248701.
Scafetta, N. and West, B.J. 2007. Phenomenological reconstructions of the solar signature in the Northern Hemisphere surface temperature records since 1600. Journal of Geophysical Research 112: 10.1029/2007JD008437.
Scafetta, N. and West, B.J. 2008. Is climate sensitive to solar variability? Physics Today 61 (3): 50-51.