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The strong correlation between Galactic Cosmic Rays (GCRs) and cloud formation has for decades been postulated as a primary mechanism for solar-driven natural climate change. Concisely, “When the Sun is active fewer cosmic rays reach the Earth and, with fewer low clouds, the world warms up” (Svensmark et al., 2017). Since about 2000, however, this GCR-cloud correlation has been violated (solar activity has declined without accompanying GCR flux), leading many to question the link. A new paper suggests this post-2000 “violation” is actually “not…unexpected”, has occurred previously, and does not undermine the Sun-GCR/cloud explanation for naturally-driven climate change.

Galactic Cosmic Rays and Low Clouds:

Possible Reasons for Correlation Reversal

“Indeed, cloudiness changes can strongly modulate fluxes of both incoming short-wave solar radiation and outgoing long-wave radiation of the Earth and the atmosphere and, thus, influence significantly the radiative-thermal balance of the atmosphere. High-level clouds contribute to the warming of the atmosphere, whereas low-level clouds contribute, as a rule, to its cooling. A net influx of radiation coming to the Earth’s surface under cloudy conditions depends on latitude, season and underlying surface. According to the data obtained from spaceborne experiments [Nimbus 7 Earth Radiation Budget experiment (N7ERB) and Earth Radiation Budget Experiment (ERBE)], when averaged over the globe, cloudiness reduces the input of solar radiation by 44.5–54.3 W·m−2 (depending on the season) and the emission of long-wave radiation to space by 23.6–34.7 W·m−2 [1, 2]. As a result, cloudiness decreases the global radiative heating of the atmosphere by 17.3–26.8 W·m−2.”

“Influence of galactic cosmic rays (GCRs) on cloud formation is suggested to be an important part of the mechanism of solar activity influence on weather and climate. A high positive correlation between low cloud amount and GCR fluxes was observed in the 1980s–1990s; however, in the early 2000s, it was violated. In this work, we consider a nature of long-term correlation links between cloud cover at middle latitudes and GCRs, as well as possible reasons for this correlation reversal. It was shown that the GCR-cloud links observed on the decadal time scale are indirect and caused by GCR effects on cyclonic activity which depend on epochs of the large-scale atmospheric circulation. The reversal of GCR-cloud correlation in the 2000s seems to be due to a sharp weakening of the Arctic and Antarctic stratospheric polar vortices, which results in the change of the troposphere-stratosphere coupling and, then, of GCR contribution to the development of extratropical cyclogenesis.”

“Correlation links observed between lower atmosphere characteristics and phenomena related to solar activity may weaken, disappear and even change sign depending on time period. So, a violation of the cloud-GCR link in the 2000s is not an extraordinary event. Herman and Goldberg [56] suggested that a reason for temporal variability of solar-atmospheric links may be long-term processes of the Sun which do not influence sunspot numbers and/or some changes of atmospheric conditions. Veretenenko and Ogurtsov [42, 43] showed that temporal behavior of correlation links between surface pressure at extratropical latitudes and sunspot numbers is characterized by a roughly 60-year periodicity caused by changes in the epochs of the large-scale atmospheric circulation. The reversals of the correlation signs were found in the end of the nineteenth century, in the early 1920s, the 1950s and the early 1980s coinciding with climatic regime shifts at middle latitudes [57], as well as with the transitions between cold and warm epochs in the Arctic [58]. So, a violation of the cloud-GCR link in the 2000s seems not to be unexpected and may be associated with the next change of the circulation epochs resulting in the change of GCR contribution to extratropical cyclonic activity and, then, to cloud field formation.”

Cloud Radiative Forcing Can Explain 1980s-2000s Warming

Cloud cover changes dominate in altering the amount of solar radiation absorbed by the Earth’s surface (Stanhill et al., 2014; Mateos et al., 2014).

With fewer clouds, more solar radiation can be absorbed by the oceans rather than reflected back to space; this, in turn, leads to warming.

Cloud cover changes and the concomitant alteration of surface solar heat absorption can therefore explain the 1980s to 2000s warming via the increase in absorbed solar radiation (Pinker et al., 2005; Pallé et al., 2004; Herman et al., 2013; Wang et al., 2012; Calbó et al., 2016; Kauppinen et al, 2014; McLean, 2014).

The GCR-Cloud “Missing Link” To Climate Change “Breakthrough”

There has recently been a scientific “breakthrough” in understanding the “missing link” between the Sun’s modulation of cosmic rays and thus cloud cover, supported by real-world observational evidence (3,100 hours of data sampling and controlled experimentation).

The following is an abbreviated list of 14 scientific papers supporting the Sunspot Activity→Cosmic Ray Flux→Cloud Cover Changes→Climate Changes conceptualization published within the last year.

Sciencedaily press release for Svensmark et al., 2017

The missing link between exploding stars, clouds, and climate on Earth

“Breakthrough in understanding of how cosmic rays from supernovae can influence Earth’s cloud cover and thereby climate”

“The new results reveal, both theoretically and experimentally, how interactions between ions and aerosols can accelerate the growth by adding material to the small aerosols and thereby help them survive to become cloud condensation nuclei. It gives a physical foundation to the large body of empirical evidence showing that Solar activity plays a role in variations in Earth’s climate. For example, the Medieval Warm Period around year 1000 AD and the cold period in the Little Ice Age 1300-1900 AD both fits with changes in Solar activity.”

“‘Finally we have the last piece of the puzzle explaining how particles from space affect climate on Earth. It gives an understanding of how changes caused by Solar activity or by super nova activity can change climate.’ says Henrik Svensmark, from DTU Space at the Technical University of Denmark, lead author of the study.

“Data was taken over a period of 2 years with total 3100 hours of data sampling. The results of the experiments agreed with the theoretical predictions.”

• Low clouds made with liquid water droplets cool the Earth’s surface.

•Variations in the Sun’s magnetic activity alter the influx of cosmic rays to the Earth.

•When the Sun is lazy, magnetically speaking, there are more cosmic rays and more low clouds, and the world is cooler.

•When the Sun is active fewer cosmic rays reach the Earth and, with fewer low clouds, the world warms up .

The implications of the study suggests that the mechanism can have affected:

• The climate changes observed during the 20th century

• The coolings and warmings of around 2°C that have occurred repeatedly over the past 10,000 years, as the Sun’s activity and the cosmic ray influx have varied .

• The much larger variations of up to 10°C occuring as the Sun and Earth travel through the Galaxy visiting regions with varying numbers of exploding stars.

Govil et al., 2018

“The spectral analysis of the sedimentological parameters reveals the significant periodicities (>95% significance) centering at ∼1067, ∼907, and ∼824 years. The long-term trends in the data suggest the possible fluctuation of Antarctic ice-sheet superimposed on global climatic fluctuations due to solar activity. … The curiosity of climate scientists arises on the mechanism of reaction of the climate system in response to the changes in solar forcing. There are two possible mechanisms proposed which work through the atmospheric processes. The first mechanism includes the action of the ozone layer by increasing more UV radiations with increased solar activity. It must have raised the temperature in the stratosphere which produces stronger winds in lower stratosphere and troposphere. These strong winds in the troposphere result in the relocation of pressure cells and storm tracks which ultimately disturbs the climate system (Schindell et al., 1999; Crosta et al., 2007). The second proposed mechanism considers the cosmic rays and cloud cover responsible for amplifying the climate forcing (Svensmark, 2000).”

“ High solar activity is believed to be responsible for less cooling of the lower atmosphere due to reduced cloud cover (Marsh and Svensmar, 2000). Conversely, low solar activity is believed to provide additional cooling of the lower atmosphere. These two feedback mechanisms responsible for the climatic forcing due to solar activity may work alone or in conjugation and are also superposed to other climate forcing as well as variability of internal cycling (Rind, 2002). Further, the periodic increase in solar activity results in increased temperature in the lower atmosphere which causes melting of ice-sheets in the Antarctic region. It may further provide the periodicity in freshwater discharge in the Schirmacher lakes and hence regulates the depositional environment of the studies lake.”

Fleming, 2018

“The results of this review point to the extreme value of CO2 to all life forms, but no role of CO2 in any significant change of the Earth’s climate. … There is no correlation of CO2 with temperature in any historical data set that was reviewed. The climate-change cooling over the 1940–1975 time period of the Modern Warming period was shown to be influenced by a combination of solar factors. The cause of the Medieval Warm Period and the Little Ice Age climate changes was the solar magnetic field and cosmic ray connection. When the solar magnetic field is strong, it acts as a barrier to cosmic rays entering the Earth’s atmosphere, clouds decrease and the Earth warms . Conversely when the solar magnetic field is weak, there is no barrier to cosmic rays—they greatly increase large areas of low-level clouds, increasing the Earth’s albedo and the planet cools.”

“Nevertheless, these results over this long period strongly suggest that the solar magnetic feld/cosmic ray interaction is the primary cause of major climate-change events over the past 9400 years of the interglacial period. The 35-year cool period within the current Modern Warming was an example where the Gleissberg cycle imposed only a modest impact on the existing strength of the magnetic feld that was in place. The current Modern Warming will continue until the strength of the Sun’s magnetic field declines.”

Utomo, 2017

“A similar result was also found for the relationship between solar activity and cosmic ray flux with a negative correlation, i.e. 0.69/year. When solar activities decrease, the clouds cover rate increase due-0.61/month and – to secondary ions produced by cosmic rays. The increase in the cloud cover rate causes the decrease in solar constant value and solar radiation on the earth’s surface. … The increase in the formation rate of cloud would affect the decrease in the intensity of solar radiation reaching the Earth’s surface. The relationship between cosmic rays and solar constant is an “opposite” relationship because of the negative correlation type (r < 0). The phenomenon of “opposite” is in a good agreement with the result by Svensmark (1997) who found a correlation between temperature and global cloud coverage with the cosmic rays… [T]he climate also depends on variations in the flux of solar energy received by the earth’s surface. Variation in the solar energy flux is caused by variations in solar activity cycle. Thus the climate is a manifestation of how solar radiation is absorbed, redistributed by the atmosphere, land and oceans, and ultimately radiated back into space. Every variation of solar energy received at the earth’s surface and reradiated by the earth into space will have a direct impact on climate change on Earth.”

Tomicic et al., 2018

“Secondary aerosol particles, which are formed by nucleation processes in the atmosphere, play an important role in atmospheric chemistry and in the Earth’s climate system. They affect the Earth’s radiation balance by scattering solar radiation back to space and can also act as cloud condensation nuclei (CCN) and thereby affect the amount of cloud and its radiative properties. Clouds have a net cooling effect on the Earth’s radiation budget of about −27.7 W m−2 (Hartmann, 1993). Thus, a small change in cloud properties can have significant effect on the climate system . Results by Merikanto et al. (2009) and Yu and Luo (2009) have shown that a significant fraction (ranging between 31 and 70 %) of cloud-forming aerosol particles in the atmosphere are secondary particles that originate from nucleation. Therefore, understanding nucleation is crucial in order to fully understand the atmospheric and climatic effects of aerosols.”

Kitaba et al., 2017

“The weakening of the geomagnetic field causes an increase in galactic cosmic ray (GCR) flux. Some researchers argue that enhanced GCR flux might lead to a climatic cooling by increasing low cloud formation, which enhances albedo (umbrella effect). Recent studies have reported geological evidence for a link between weakened geomagnetic field and climatic cooling. … Greater terrestrial cooling indicates that a reduction of insolation [solar radiation reaching the surface] is playing a key role in the link between the weakening of the geomagnetic field and climatic cooling. The most likely candidate for the mechanism seems to be the increased albedo of the umbrella effect.”

Frigo et al., 2018

“In this work, we investigate the relationship between the ∼ 11-year and ∼ 22-year cycles that are related to solar activity and GCRs [galactic cosmic rays] and the annual average temperature recorded between 1936 and 2014 at two weather stations, both located near a latitude of 26◦ S but at different longitudes. … Sunspot data and the solar modulation potential for cosmic rays were used as proxies for the solar activity and the GCRs, respectively. Our investigation of the influence of decadal and bidecadal cycles in temperature data was carried out using the wavelet transform coherence (WTC) spectrum. The results indicate that periodicities of 11 years may have continuously modulated the climate at TOR [Torres, Brazil] via a nonlinear mechanism … The obtained results offer indirect mathematical evidence that solar activity and GCR variations contributed to climatic changes in southern Brazil during the last century . The contribution of other mechanisms also related to solar activity cannot be excluded.”

Biktash, 2017

“The effects of total solar irradiance (TSI) and volcanic activity on long-term global temperature variations during solar cycles 19–23 [1954-2008] were studied. It was shown that a large proportion of climate variations can be explained by the mechanism of action of TSI [total solar irradiance] and cosmic rays (CRs) on the state of the lower atmosphere and other meteorological parameters. … Recent studies by Pudovkin and Raspopov, Tinsley, and Swensmark have shown that the Earth’s cloud coverage is strongly influenced by cosmic ray intensity . Conditions in interplanetary space, which can influence GCRs and climate change, have been studied in numerous works. As has been demonstrated by Biktash, the long-term CR count rate and global temperature variations in 20–23 solar cycles are modulated by solar activity and by the IMF (interplanetary magnetic field). A possible geophysical factor which is able to affect the influence of solar activity on the Earth’s climate is volcanism. The effects of volcanism can lead to serious consequences in the atmosphere and the climate.”

Wilson and Sidorenkov, 2018

“The fact that the periods of eight out of nine of the most prominent peaks in the lunar alignment spectrum (highlighted column 3 of Table 2) closely match those in the spectra of ϕm [solar modulation potentional] and Tm [maximum daily temperature], strongly supports the contention that all three of these phenomena are closely related to one another. … principal component analyses of the 10Be and 14C records show that, on multi-decadal to centennial time scales, the radionuclide production signal accounts for 76% of the total variance in the data [18,19]. This would imply that there is a causal link between Tm [maximum daily temperature] and near-Earth GCR flux, with a factor related to the latter driving the former . … An implicit assumption that is used by those who reject GCR [galactic cosmic rays]-cloud models is that the GCR flux hitting the Earth needs to produce changes in the total amount of cloud cover over the majority of the globe in order to significantly affect the world mean temperature. However, this assumption ignores the possibility that regional changes in the amount of cloud cover could influence the rate at which the Earth’s climate system warms or cools. Of course, for this to be true there would have to be observational evidence that shows that the GCR flux can affect the level of cloud cover on a regional scale. Support for this hypothesis is provided [23] who claim that existing multi-decadal ground-based datasets for clouds show that there is a weak but significant correlation between the amounts of regional cloud cover and the overall level of GCR fluxes. In addition, Larken et al. [2010] find that there is a strong and robust positive correlation between statistically significant variations in the short-term (daily) GCR ray flux and the most rapid decreases in cloud cover over the mid-latitudes (30° – 60° N/S). Moreover, Larken et al. [2010] find that there is a direct causal link between the observed cloud changes and changes in the sea level atmospheric temperature, over similar time periods.” “Hence, the solar connection between Tm and ϕm can be summarized using a heuristic luni-solar model like that shown in Figure 6. Firstly, the model proposes that there must be some, as yet, unknown factor associated with the level of solar activity on the Sun (e.g. possibly the overall level GCR hitting the Earth) that is producing long-term systematic changes in the amount and/or type of regional cloud cover. Secondly, the model proposes that the resulting changes in regional cloud cover lead to variations in the temperature differences between the tropics and the poles which, in turn, result in changes to the peak strength of the zonal tropical winds. Thirdly, the model further proposes that it is the long-term changes in the amount and/or type of regional cloud cover, combined with the variations in the temperature differences between the tropics and the poles that lead to the long-term changes in the poleward energy and momentum flux. And finally, the model proposes that it is this flux which governs the rate at which the Earth warms and cools, and hence, determines the long-term changes in the world mean temperature.”

Vieira et al., 2018

“Galactic cosmic rays (GCRs) are the main source of ionizing radiation in the lower troposphere, in which secondary products can penetrate the ground and underground layers. GCRs affect the physical–chemical properties of the terrestrial atmosphere, as well as the biosphere. GCRs are modulated by solar activity and latitudinal geomagnetic field distribution .”

Tyasto et al., 2018

“Variations of charged particles of galactic cosmic rays (GCRs), which are caused by variations in the Earth’s magnetic field, are one of most significant among the variety of phenomena that influence the near-Earth medium and, consequently, the Earth’s climate and weather. Being the main sources of atmospheric ionization, they influence the atmosphere transparency and play the key role in formation of clouds, thunderstorms, and lightnings (Dorman, 2009).”

Luthardt and Rößler, 2017

“The 11 yr solar cycle, also known as Schwabe cycle, represents the smallest-scaled solar cyclicity and is traced back to sunspot activity (Douglass, 1928; Lean, 2000), which has a measurable effect on the Earth’s climate, as indicated by the Maunder minimum (Usoskin et al., 2015). Global climate feedback reactions to solar irradiance variations caused by sunspots are complex and hypothesized to be triggered by (1) variation in total energy input (Cubasch and Voss, 2000), (2) the influence of ultraviolet light intensity variation on composition of the stratosphere (Lean and Rind, 2001), (3) the effect of cosmic rays on cloud formation (Marsh and Svensmark, 2000; Sun and Bradley, 2002), and/or (4) the effect of high-energy particles on the strato- and mesosphere (Jackman et al., 2005). … [L]ike today, sunspot activity caused fluctuations of cosmic radiation input to the atmosphere, affecting cloud formation and annual rates of precipitation .”

Palcsu et al., 2018

“The relationship between the atmospheric concentration of cosmogenic isotopes, the change of solar activity and hence secondary neutron flux has already been proven. The temporal atmospheric variation of the most studied cosmogenic isotopes shows a significant anti-correlation with solar cycles. However, since artificial tritium input to the atmosphere due to nuclear-weapon tests masked the expected variations of tritium production rate by three orders of magnitude, the natural variation of tritium in meteoric precipitation has not previously been detected. For the first time, we provide clear evidence of the positive correlation between the tritium concentration of meteoric precipitation and neutron flux modulated by solar magnetic activity. We found trends in tritium time series for numerous locations worldwide which are similar to the variation of secondary neutron flux and sun spot numbers. This variability appears to have similar periodicities to that of solar cycle. Frequency analysis, cross correlation analysis, continuous and cross wavelet analysis provide mathematical evidence that the correlation between solar cycle and meteoric tritium does exist. Our results demonstrate that the response of tritium variation in precipitation to the solar cycle can be used to help us understand its role in the water cycle.”

Padovani et al., 2018

“The presence of small amounts of atomic hydrogen, detected as absorption dips in the 21 cm line spectrum, is a well-known characteristic of dark clouds. The abundance of hydrogen atoms measured in the densest regions of molecular clouds can be only explained by the dissociation of H2 due to cosmic rays. … Our findings show that a careful description of molecular hydrogen dissociation by cosmic rays can explain the abundance of atomic hydrogen in dark clouds. An accurate characterisation of this process at high densities is crucial for understanding the chemical evolution of star-forming regions.”