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New papers show clear impact by solar activity on the earth’s climate. Images: NASA Earth Observatory.

By Dr. Sebastian Lüning and Prof. Fritz Vahrenholt

(German text translated by P Gosselin)

It’s been claimed time and again that solar activity cycles for the most part can be neglected climatically. They hardly have any impact. Therefore it is all the more amazing when almost every month a new scientific study comes out that documents the exact opposite.

One example comes from November 2016 when the Geophysical Research Letters published a paper by Adrián Martínez-Asensio et al on the impact of solar activity on sea level. The scientists documented that the autumn sea level extreme in Venice and Triest are in fact controlled by the 11-year solar cycle.

In the wintertime the sun’s impact is seen at other coastal locations, namely Marseille, Ceuta, Brest and Newlyn. What follows is the paper’s fascinating abstract:

Decadal variability of European sea level extremes in relation to the solar activity

This study investigates the relationship between decadal changes in solar activity and sea level extremes along the European coasts and derived from tide gauge data. Autumn sea level extremes vary with the 11 year solar cycle at Venice as suggested by previous studies, but a similar link is also found at Trieste. In addition, a solar signal in winter sea level extremes is also found at Venice, Trieste, Marseille, Ceuta, Brest, and Newlyn. The influence of the solar cycle is also evident in the sea level extremes derived from a barotropic model with spatial patterns that are consistent with the correlations obtained at the tide gauges. This agreement indicates that the link to the solar cycle is through modulation of the atmospheric forcing. The only atmospheric regional pattern that showed variability at the 11 year period was the East Atlantic pattern.”

Another example is found in March, 2016. Jordahna Ellan-Ann Haig and Jonathan Nott reconstructed the tropical cyclone history of Australia for the past 1500 years. Here they discovered that the observed variability was mostly controlled by solar activity over decades and centuries. Haig and Nott hope that future tropical storm forecasts can benefit from the important solar factor.

The paper’s abstract follows:

Solar forcing over the last 1500 years and Australian tropical cyclone activity

Accurate seasonal and decadal predictions of tropical cyclone activity are essential for the development of mitigation strategies for the 2.7 billion residents living within cyclone prone regions. The traditional indices (Southern Oscillation Index and various sea surface temperature indices) have fallen short in recent years as seasonal predictors within the Australian region. The short length of these records (i.e., <50 years) has meant that our current knowledge of larger-scale drivers at interdecadal, centennial, and millennial scales is limited. The development of a new tropical cyclone activity index spanning the last 1500 years has enabled the examination of tropical cyclone climatology at higher temporal resolution than was previously possible. Here we show that in addition to other well-known climate indices, solar forcing largely drives decadal, interdecadal, and centennial cycles within the tropical cyclone record.”

Lastly there’s a fairly recent example from South America. Andrés Antico and Maria Tores examined the discharge rate of the Amazon for the last 100 years in an article published in 2015. They discovered that the development is very closely coupled to solar fluctuations. The paper’s abstract follows:

Evidence of a decadal solar signal in the Amazon River: 1903 to 2013

It has been shown that tropical climates can be notably influenced by the decadal solar cycle; however, the relationship between this solar forcing and the tropical Amazon River has been overlooked in previous research. In this study, we reveal evidence of such a link by analyzing a 1903–2013 record of Amazon discharge. We identify a decadal flow cycle that is anticorrelated with the solar activity measured by the decadal sunspot cycle. This relationship persists through time and appears to result from a solar influence on the tropical Atlantic Ocean. The amplitude of the decadal solar signal in flow is apparently modulated by the interdecadal North Atlantic variability. Because Amazonia is an important element of the planetary water cycle, our findings have implications for studies on global change.”