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German Professor Fritz Vahrenholt and Frank Bosse present the solar report for October 2015. The current cycle continues to be a weak one.

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By Frank Bosse and Fritz Vahrenholt

[Translated/edited by P Gosselin]

In October, 2015, our mother star was less active than in September. The solar sunspot number (SSN) was 61.7, only 72% of what is normal this month into the cycle compared to the mean of the observed cycles since occurring 1755. In detail:

Fig. 1: Our current Solar Cycle 24, which started in December 2008, is shown by the red curve and is compared to the mean cycle (blue) and to the very similar solar cycle 5 shown by the black curve.

What really stands out are negative anomalies that occurred during the cycle ramp-up and the ensuing plateau phase. Until the 54th month the sun was only 47% as active as the mean. But later beginning at about month number 62 the current cycle followed along below the mean closely. Since then the current cycle has been tracing at about 73% of the mean value. Over the entire cycle so far the current cycle has been running on average at 56% of the mean. What follows is a comparison of all cycles:

Fig. 2: Comparison of all the cycles. The bars represent the SSN anomaly from the mean for 83 months into the cycle.

One clearly sees the activity hump in the middle of the 20th century, from SC 17 to SC 23. This was recently investigated at a conference at the end of October, 2015, which worked out the solar forcing for a new generation of climate models (CMIP6):

Fig. 3: Solar forcing for new climate models, source: Matthes & Funke 2015.

The contribution by Katja Matthes of the Geomar Center in Kiel, Germany and Bernd Funke of the Astrophysical Institute in Granada sees an increase of approximately 1 W/m² on average between 1880 and the level of 1950 to 2000 (light blue curve in Fig 3). Now a prediction until 2075 sees a drop in value to that of 1880 (grey in Fig. 3). One, however, does need to be careful with the forecast. The sun is a very dynamic star. Yet, the assumption that the solar irradiance is constant, which was the case in the older models (CMIP5 in light green), is being abandoned.

Today the solar forcing of the sun is assumed to be greater by a factor of 5 over what was assumed just a few years ago (e.g. Feulner & Rahmstorf 2010) when conventional climate science and also the IPCC accounted for a solar irradiance TSI variation of only 0.2W/m².

Clearly the sun is gaining more influence in the world of climate modeling, as it is getting neglected less in the new models. However we will not being hearing anything about these findings from the media during the upcoming Paris conference: There the sun will have no effect on our current climate. The only thing of any concern in Paris is trace gas CO2.