PNAS Study Shows Powerful Correlation Between Sun And Climate Over The Last 9000 Years

By Dr. Sebastian Lüning and Prof. Fritz Vahrenholt
(Translation / editing by P Gosselin)
The IPCC thinks the sun plays nary a role on climate and that anthropogenic factors explain almost the entire warming since 1850.

It’s been completely ignored that Gerard Bond was able to show more than 10 years ago that the last 10,000 years have been characterized by a global temperature roller coaster that runs up and down in sync with solar activity (Bond et al. 2001).

Figure 1: Comparison of solar activity (blue curve) and the Asian climate development (green curve, delta ¹⁸O of a stalagmite in a Chinese cave) for the last 9000 years (both curves normalized). One clearly sees a good agreement between the two curves, which stgrongly suggests a significant climate impact by the sun. Figure from Steinhilber et al. (2012).

In our book “The Forgotten Sun“ (p. 68-75) we were able to show the close relationship between the climate and the sun in multiple studies from all parts of the globe and that the warming of the last 150 years also closely follows the pattern.

Now a new paper by the international team of scientists led by Friedhelm Steinhilber of the Swiss Federal Institute for Aquatic Sciences and technology (Eawag) has just produced yet more important evidence of the sun’s impact on the Holocene climate development. The group, which also includes glaciologist Hans Oerter of the Alfred Wegener Institute in Bremerhaven, Germany, published the results last month in the Proceedings of the National Academy of Sciences (PNAS).

Using multiple Antarctic and Greenland ice cores and global tree-ring data, the scientists reconstructed solar activity over the last 9000 years. They also used the so-called cosmogenic beryllium and carbon isotopes 10Be and 14C, whose frequency on Earth is controlled by the strength of the sun’s magnetic field, and thus by solar activity.

The group carried out a spectral analysis of the new solar activity curves and found, as expected, the usual characteristic solar cycles, among them also the 210-year Suess-de Vries cycle, the 1000-year Eddy-cycle and the 2300-year Hallstatt-cycle. The Grand Solar Minima coincided mostly with the minima of the Suess-de Vries cycles.

The cycles are superimposed by the longterm rising and falling signal of orbital changes associated with the Milankovitch cycles. The Milankovitch cycle is in part responsible for the warm temperatures of the Holocene Optimum 6000 years ago, when it was considerably warmer than today. Steinhilber and his colleagues removed these orbital signals from the data in order to filter out the primary solar activity.

They then compared the new solar activity reconstruction with a climate dataset earlier obtained by colleagues in a Chinese cave covering the last 9000 years. The fluctuations in the ¹⁸O-oxygen isotope concentrations show the precipitation fluctuations and the intensity of the Asian monsoons. What resulted was a surprising agreement between solar activity and the Asian climate development (see Figure 1 above).

In times of low solar activity, Asian monsoons were less pronounced in general. Also the most important solar cycles could be found in the frequency analysis of the Asian climate signal. One can only conclude that solar activity cycles are the main driver of the last 10,000 years and that they continue to be so today as we continue to remain in the now well-documented pattern.

In the 9000-year time period investigated by Florian Steinhilber and his colleagues, there are however some phases where the correlation between solar activity and climate is missing. For these periods, the scientists assume that other geological factors, like large volcanic eruptions and associated atmospheric aerosols, or other natural factors influenced and overrode the solar signal. In general these factors must always be taken into account when conducting statistical analyses.

The new results from the Steinhilber Group once again shows the significant importance of the sun on the Earth’s climate development.

We can only hope that the authors of the current, new IPCC report will add it and all the other important studiesn in its synthesis report and finally add the sun’s major impact in the models. However, this only hopeful thinking. In contradiction to the growing body of scientific evidence, the IPCC has already made it clear that it will ignore the sun’s major impact even more (see our blog article “Der neue IPCC-Klimabericht: Sonne noch weiter degradiert!“).

This needs to be seriously looked into.