Empirical Harmonic Models Project "Sunnier" Climate Scenarios Ahead
Scafetta, N. 2012. Testing an astronomically based decadal-scale empirical harmonic climate model versus the IPCC (2007) general circulation models. Journal of Atmospheric and Solar Terrestrial Physics doi:10.1016/j.jastp.2011.12.005.
Several studies have shown that GCMs are improving on the ability to reproduce the current climate including intraseasonal and interannual variations. The ability of the GCMs to capture internal non-linear processes, however, will always be suspect. But, when examining climate, important external forcing processes need to be accounted for, including such natural processes as volcanic activity and solar variations. There is also increasing evidence that extraterrestrial forcing processes are having an impact on solar variations, and, thus, terrestrial climate.
Scafetta (2011) explored several such issues in his latest work. First, he expanded on his own recently published work demonstrating a link between well-known climate cycles of roughly 10, 20, and 60 years to celestial cycles. The celestial cycles result from the solar-lunar tidal oscillation (9.1 years), and gravitational cycles related to the interaction between the sun and the largest planets (Jupiter and Saturn). These cycles have periods of about 10, 20, and 60 years. A paper by Loehle and Scafetta (2011) demonstrated that these cycles, in addition to a realistic anthropogenic effect, can be added together to reconstruct the global climate record since 1950. They also show that this empirical model can be used to project climate into the 21st century.
Scafetta (2011) also reports that the IPCC GCMs cannot capture decadal and interdecadal variability. As shown by the author (here Fig. 1, below); "although these GCM simulations present some kind of red-noise variability supposed to simulate the multi-annual, decadal, and multidecadal natural variability, a simple visual comparison among the simulations and the temperature record gives a clear impression that the simulated variability has nothing to do with the observed temperature dynamics."
Next, Scafetta demonstrates that natural variability is not solely the result of internal variations, but that the external forcing described above also plays a role. These external forcings modulate solar output, which in turn impacts electrical activity in the upper atmosphere. This influences incoming cosmic ray fluxes, which have been liked to variability in cloudiness. These external cycles have similar periods to internal climate variations. Natural variations, therefore, likely account for more than half the climate variability since 1850.
Figure 1. Adapted from Scafetta (2011) Figure 1. The global surface temperature taken from http://www.cru.uea.ac.uk/cru/data/temperature/ (black) and the GISS ModelE average simulation (blue), and a fit using an empirical harmonic model (red).
Finally, Scafetta concludes that the IPCC erroneously ascribes all of the climate change to anthropogenic forcing. When the anthropogenic effect is corrected, it accounts for less than half the recent climate change. Additionally, Scafetta shows that the empirical model in his paper projected the cooling of the most recent decade, whereas the IPCC GCMs produced a quasi-monotonic warming of the climate from about the year 2000 on. Furthermore, Scafetta's model produces a warming of only 0.8-1.5°C by the end of the 21st century.
Skeptics have long cautioned the public about the shortcomings of the IPCCs reliance on GCMs in producing climate change scenarios for the next century. In addition to well-documented problems with model numerics, the lack of data, and chaos, the model physics fall short. This is true not only for such internal processes as cloud physics, but also for such external forcing as sun-moon tidal forcing, and other solar system gravitational cycles which influence solar output. This work demonstrates that there is increasing evidence that our very solar system is playing a significant role in decadal and multidecadal climate variations. As such, the climate projections produced by Scafetta's empirical harmonic model are likely more realistic and are certainly more optimistic.
Loehle, C. and Scafetta, N. 2011. Climate Change Attribution Using Empirical Decomposition of Climatic Data. The Open Atmospheric Science Journal 5: 74-86.