From KlimaNachrichten

By Dr. Ludger Laurenz

Summary and outlook:

• Changes in precipitation and drought intensity in Germany over the last 10 years are primarily based on the Sun’s 22-year Hale cycle and not on anthropogenic influence. This can be proven with the help of historical climate data from Münster/NRW. The surprisingly strong solar influence in the weather trend of Münster can be detected in all federal states, the Benelux countries and northern France.
• The solar-induced fluctuation range of the annual precipitation total of about 100 mm in the four-year average and 300 mm, in relation to the individual year, is much larger than changes that are attributed to anthropogenic climate change. The influence of the Sun’s Hale cycle on precipitation and drought trends can be used for monthly, seasonal and multi-year forecasts (Climate News 2025).

• If the influence of the 22-year Hale cycle on the rainfall and drought trend of months and years is so clear and serious, then it is not surprising that numerous recent research papers have demonstrated solar influence on the temperature trend of recent decades (Google Scholar).
                                                                                      
• Uncovering links between varying solar activity and weather trends shows the potential that climate research could use to place current changes in precipitation patterns and drought intensity in the context of natural influences such as solar and ocean cycles. We need a paradigm shift in climate science. The assumption that primarily anthropogenic causes are responsible for the precipitation patterns and drought intensity of recent years cannot be maintained against the background of solar influence.                                                                   
• The German Weather Service is informed about the new findings on the solar influence on the precipitation trend. They were noted there with interest. The German Weather Service has contacted a German university to further investigate the topic scientifically. If the results are positive, it is possible to test an application for the DWD seasonal forecasts.

The influence of cyclically fluctuating solar activity on weather and climate has been proven in thousands of scientific publications. Against this background, I first searched for traces of the 11-year sunspot cycle or Schwabe cycle of the sun in historical weather data from Germany in recent years. The results have been published in a publication in which I was involved (Laurenz et al. 2019 ). In recent years, I have primarily dealt with the influence of the approximately 22-year magnetic cycle or Hale cycle (with varying lengths from 20 to 23 years) on the weather and have written several articles for Klimanachrichten.de. In my search for solar influence, the focus is on precipitation, where solar influence is more clearly reflected than in temperature or sunshine duration.

From 2018 to 2022, several years of severe drought occurred in Germany. In contrast, the last two years were extremely rainy. This change was influenced or even caused by cyclically fluctuating solar activity. This article will be proven with the help of historical climate data from the Münster/NRW region.

With the help of the average of the annual precipitation total of several years, solar influence can be detected more reliably than with individual year data.

So far, I have been looking for the solar influence on the precipitation total in the weather data of individual years. Recently, I came across the globally used and available drought index SPEI (SPEI). At SPEI, drought data for different periods of 1 to 48 months are available. For example, to calculate the SPEI (48), the total precipitation and evaporation of the past 48 months are balanced.

With the idea of the 48-month period, I tried out whether a solar influence on precipitation activity could be detected with the help of a 48-month average of the past 4 years. The result is described using the example of the monthly precipitation total of Münster/NRW dating back to 1853. During this period, 8 Hale cycles are repeated.

Close relationship between the mean annual precipitation total of the last four years and the Hale cycle of the Sun

The method for detecting solar influence is relatively simple. First, the average of the past four years is calculated for each individual year since 1856. The course of the data series obtained in this way is shown in Figure 1. On the basis of the averaging, a repetitive up and down of the trend can be seen, which is not disturbed by individual annual results.

The data series is then “cut up” at the beginning of the 8 starting years of the Sun’s Hale cycles (see Figure 1). If the 8 sections are “superimposed”, Figure 2 is created.

During the 22-year Hale cycle, the precipitation totals of all Hale cycles follow more or less a common trend. This is evidence of solar influence, which repeats itself about every 22 years according to a similar pattern.

The strength of the solar signal is surprising. The black mean line drops after the maximum of 797 mm to the minimum of 686 mm and rises rapidly in the second half of the Hale cycle within only 5 cycle years almost to the maximum of the first cycle year. These 5 cycle years are just behind us in 2025. With a fluctuation range of approx. 100 mm on the four-year average, the solar influence on the annual precipitation total is of great economic importance with regard to the effects on agriculture, forestry, river navigation or water management.

The range of fluctuation caused by solar, which has been detected here for the first time, is about 100 mm (and about 300 mm in relation to the individual year Laurenz 2024), much larger than changes that are attributed to anthropogenic climate change. The main driver of the precipitation trend in recent years is obviously the variation in solar activity.

The differentiation between the curves of the individual Hale cycles is revealing. The 5 Hale cycles from 1881 to 1968 with the thin lines run close together. Three specially marked curves protrude upwards and downwards. The cycle with the green line starting in 1988 shows the highest precipitation totals, the cycle starting in 2011 shows the lowest, similar to the cycle starting in 1881.

The latter three cycles, with the strikingly strong deviations upwards and downwards, are also characterized by the fact that these deviations are more or less maintained over the entire course of the 22-year cycle. For example, at the start of the Hale cycle in cycle year 1 (bottom left in Figure 2), it could already be determined which energy program the sun will reel off in the next 22 years. That would be an exciting topic for solar physicists.

The 8 curves do not show a directional trend over 166 years. The current low-precipitation cycle starting in 2011 is preceded by the exceptionally rainy cycle starting in 1988. The lack of rain in the current cycle is not new. The level of precipitation was similarly low in the cycle beginning in 1858.

Regarding the supposed contradiction between the current drought in Germany and the current phase of the Hale cycle with very high precipitation levels overall: The current year 2025 is in the middle of the cycle phase with very high annual precipitation total, averaged over four years, in cycle year 15. How can we explain that in 2025 from February to May, at least in the northern half of Germany, record-breaking little precipitation has fallen? This is also likely to be influenced by solar activity. In cycle year 15, the annual precipitation total temporarily decreases by 100 to 200 mm on average over the last 8 Hale cycles compared to the previous year, only to rise again in the following year (cycle year 15). The year 1959, with the lowest annual precipitation total since 1853 in Münster, is also in cycle year 15.

There are 66 years between 1959 and 2025. The period length of another solar cycle is about 65 years. Will extreme droughts repeat themselves in the cycle year 15 at a rhythm of 66 years? 66 years before 1959 is 1893. In that year, it was also extremely dry in Münster in the first half of the year.

For skeptics and critics

The curve in Figure 2 appears to be chaotic at times in the first half of the Hale cycle. From this it could be concluded that the solar influence is not clearly proven by Figure 2. To counter this criticism, I have cut out the period 1881 to 1987 with 5 consecutive Hale cycles and shown separately in Figure 3. I hope that no one accuses me of “cherry picking” in this selection.

All curves follow a common trend, evidence of solar influence, which repeats itself approximately every 22 years according to the same pattern. The main driver of different precipitation trends over the course of the 22-year Hale cycle is the variation in solar activity.

Close relationship between the SPEI drought index (48) and the Sun’s Hale cycle

After the discovery of the solar influence in the four-year average annual precipitation total, I was curious about the result of the four-year drought index SPEI (48). The SPEI (Standardized Precipitation Evapotranspiration Index) is a globally used and available index for the identification of drought and moisture situations (SPEI Data). The SPEI can be used to determine the extent of drought conditions compared to normal conditions in a variety of natural and managed systems such as crops, ecosystems, rivers, water resources, etc.

SPEI values close to 0 represent near-normal conditions, while positive or negative values represent above- or below-average conditions. The SPEI indicates how much the difference between precipitation and evaporation is above or below the mean value, cumulatively over a certain period of time, e.g. 3 months, 6 months, 12 months or 48 months.

Figure 4 shows the course of the SPEI (48) for the Münster region.

In Figure 4, multi-year phases with positive and negative values alternate relatively evenly. Whether this change is due to the influence of the Sun’s Hale cycle can be determined using the same method as before for the precipitation total. To do this, I divided the SPEI (48) data series, which has been available since 1905, into the sections of the individual Hale cycles and superimposed them, with the result in Figure 5.

The influence of the Hale cycle is also visible in the SPEI (48). In Figure 5, all 6 curves follow a common trend, as evidence of solar influence. In the first half of the Hale cycle, the black mean line sinks to almost minus one (moderate drought) with a small intermediate high, and then rises steeply to 0.8 (too wet). The solar influence on the annual precipitation total, with the fluctuation range of almost two index values, can be used for forecasts and is therefore very interesting and economically significant for agriculture, forestry, shipping or water management.

In the case of SPEI (48), the differentiation between the curves of the individual Hale cycles is also revealing. The first 4 Hale cycles from 1903 to 1968 with the thin lines run close together. Two specially marked curves protrude upwards and downwards. The cycle with the green line, which begins in 1988, shows the highest index or humidity values, while the red cycle, which starts immediately afterwards in 2011, shows the strongest drought values.

The 6 curves do not indicate a directional trend over 119 years. Each cycle is presumably individually influenced by the fluctuating solar activity, which not only varies in 22-year cycles, but is superimposed and influenced by longer solar cycles of about 65/66, 100, 200 and 2300 years.

Close relationship between the SPEI drought index (24) and the Sun’s Hale cycle

After the discovery of the solar signal in the SPEI (48), I also searched for solar influence in the SPEI (24) with values accumulated over 24 months. The result is shown in Figure 6.

Naturally, the curves for the SPEI (24) in Figure 6 vary more than for the SPEI (48) in Figure 5. Nevertheless, the 6 curves follow a common trend at times, which can once again be seen as evidence of solar influence. The drought index forms a pronounced minimum in cycle year 10. The differences between the curves starting in 1988 and 2011, which are highlighted in green and red, are similar to those of the SPEI (48) and the annual precipitation total. A linear trend over the 119 years, which could have been triggered by the increase in the concentration of greenhouse gases, for example, is also not recognizable in this figure. The main driver of the trend is the variation in solar activity.

Why has the influence of the Hale cycle on the precipitation and drought trend in Germany not yet been discovered at research institutes?

The proven method for detecting cycles in historical data series is Fourier analysis. Reports on the detection of the 22-year Hale cycle in historical weather data series from Germany with the help of Fourier analysis cannot be found. Why could it be that the influence of the approximately 22-year Hale cycle, which is evident in Figures 2, 3, 5 and 6, cannot be detected by Fourier analysis and has not yet been discovered? The cause may lie in the period length of the Hale cycles, which fluctuates between 20 and 23 years. With such varying phase length, Fourier analysis obviously fails.

Detection of solar influence exacerbates the crisis of climate science

Recently, I came across the following press release (2025): “More and more often, the forecasts of climate models deviate from reality. Axel Bojanowski has let two scientists from the Max Planck Institute for Meteorology in Hamburg have their say. Prof. Björn Stevens and Prof. Jochem Marotzke speak of a crisis in climate science. Marotzke: “The current class of climate models runs into too many contradictions with reality.” Marotzke is worried about the great uncertainty of the models. As examples, he cites: “In large parts of the world, the models contradict each other on the question of whether it will rain more or less in the future. With regard to climate science, he speaks of “the other climate crisis”. This is the moment for a paradigm shift.”

The evidence of solar influence on the precipitation and drought trend in Germany underpins the need for a fundamental rethink. The previous assumption that primarily anthropogenic causes are responsible for the precipitation patterns and drought intensity of recent years can no longer be maintained against the background of solar influence. The issue of climate is far too complex to be able to reduce current changes unilaterally to anthropogenic causes.