Variations on Sun’s role in climate change

It is good that Physics Today reported on the work of Nicola Scafetta and Bruce West. They have done by far the best work in relating solar variability to terrestrial climate, bringing sophistication and rigor to a field dominated mostly by unsupportable positions that the Sun’s effect is negligible on the one hand, or is responsible for nearly all observed global warming on the other. That solar variability has appreciable coupling to Earth’s climate becomes obvious when an observer notes the imprint of the Schwabe sunspot cycle on the climate temperature record. ¹ The identical scaleless noise spectra for solar and terrestrial climate fluctuations provide additional support for coupling and for regarding the Earth–Sun network as a complex system.

Unfortunately, the Intergovernmental Panel on Climate Change clings to its position that solar variability effects are negligible, to the detriment of its credibility. Given known solar variability, the IPCC position can be rationalized only if the so-called hockey-stick global temperature reconstruction, ² which shows little natural variation, is valid. However, that reconstruction is at odds with natural history and has been shown to be statistically flawed; ³ more recent reconstructions ^4,5 show much more natural variation. The fact that general circulation models do not give appreciable Sun–Earth coupling merely shows that they are leaving out essential physics—by no means their only serious shortcoming. Unfortunately, the phenomenological approach of Scafetta and West only informs us of the magnitude of the climatic impact of solar variability. It does not shed light on the actual physical mechanisms, so it points to the need for more research on physical coupling mechanisms between those interacting complex systems.

It is also unfortunate that Physics Today chose to feature this work as an Opinion, rather than giving it the fullfledged article status it deserves. The readership should be informed in more detail about this important work.