Solar and Planetary Influences on Global Climate Change
Scafetta, N. 2013. Solar and planetary oscillation control on climate change: Hind-cast, forecast and a comparison with the CMIP5 GCMs. Energy & Environment 24: 455-496.
As an alternative to the IPCC's approach to the subject, Scafetta describes an empirical model that uses: "a specific set of decadal, multi-decadal, secular and millennial astronomic harmonics to simulate the observed climatic oscillations," plus "a 0.45 attenuation of the GCM ensemble mean simulation to model the anthropogenic and volcano forcing effects." And what are the results of this approach?
Scafetta reports that his proposed empirical model "outperforms the GCMs by better hind-casting the observed 1850-2012 climatic patterns." More specifically, he notes that "about 50-60% of the warming observed since 1850 and since 1970 was induced by natural oscillations likely resulting from harmonic astronomical forcings that are not yet included in the GCMs."
The way Scafetta sees things, "the results of this analysis indicate that the GCMs do not yet include important physical mechanisms associated with natural oscillations of the climate system." And, therefore, he suggests that interpretations and predictions of climate change based on current GCMs, including the CMIP5 GCMs to be used in the IPCC AR5, are "questionable."