Sun Power, Part 2

It was Galileo, using his newly invented telescope, who, around 1600, saw sunspots for the first time in western history. From that point forward, sunspot observations were made on a regular basis by astronomers throughout Europe.

Sunspot observations had also been made by the Chinese around 800 AD.

In 1800, an astronomer, Herschel, was struck by the eleven-year sunspot cycle, and the perceived variation in commerce every ten years. Turning to Adam Smith’s Wealth of Nations, he found data about the price of wheat that varied with the sunspot cycle. When sunspots were few in number, the price of wheat was high, and when sunspots were plentiful, there were abundant harvests and the price of wheat was low.

With this rudimentary idea that sunspots were related to climate, other astronomers, often sustaining criticism from their peers, searched for more data that could establish a stronger link between sunspots and climate.

Dramatic evidence of a strong linkage was provided by another astronomer, Walter Maunder, who at the age of 70, in 1922, linked the lack of sunspots between 1645 and 1715, to the bitter cold of that period.

It wasn’t until the 1970s, when Dr. Jack Eddy focused attention on Maunder’s work, that the significance of the Maunder Minimum became understood.

Sun Spot chart from NASA
Sun Spot chart from NASA

The Maunder Minimum is believed to have been the cause of the Little Ice Age. The Dalton Minimum is the period during the first two cycles beginning around 1800.

The 20th century seems to have been a period where sunspots were more frequent, especially from 1950 to 2000, while the most recent cycles in the 21st century have had fewer sunspots.

The forecast is for cycle 25 to be smaller in number than cycle 24, shown to the right of this photo, which is the smallest number of sunspots since cycle 14 that reached its peak around 1912.

Sun Spot Cycle 24 as of January 2015
Sun Spot Cycle 24 as of January 2015

Even if there is a causal relationship between sunspots and climate, it has only been recently that a mechanism for the linkage has been proposed.

In 1997, Dr. Svensmark, a Danish scientist at the Danish National Space Institute, proposed that sunspot eruptions affected the strength of the sun’s magnetic field, which in turn, affected the earth’s magnetic field.

When the magnetic fields surrounding the earth were strong, during periods of high sunspot activity, cosmic rays were deflected away from the earth. When there were few sunspots, during periods of low sunspot activity, cosmic rays could enter the earth’s atmosphere and affect the earth’s climate.

Svensmark suggested that cosmic rays could affect low level cloud formation, with more cosmic rays creating more low level clouds. He proposed that an increase in low level cloud coverage would result in lower temperatures as they acted like a shade over the earth, while also reflecting more sunlight away from the earth’s surface.

The major controversy surrounding Svensmark’s hypothesis was whether cosmic rays could induce cloud formation.

In 2007, Svensmark conducted a laboratory experiment that seemed to confirm that cosmic rays could induce cloud formation.

The debate then resulted in the Cloud experiment at CERN, Europe’s premiere research center.

The Cloud experiment proved, with little doubt, that cosmic rays can induce cloud formation.

Professor Nir Shaviv, Hebrew University, Jerusalem, explains all of this, plus the results of computer projections using the effects of low level clouds on temperatures, in a 37 minute presentation. The presentation is available at

Svensmark has provided an explanation for how the sun, or more specifically sunspots, can affect climate change.

While this is admittedly only a hypothesis, it has substantial scientific underpinning going back several hundred years, and perhaps longer.

This is in contrast with the CO2 hypothesis that’s based on data going back only a hundred years or so.

In addition, the sunspot hypothesis is consistent for hundreds of years, at least back to 1600, while the data supporting the CO2 hypothesis is not consistent.

From the mid 1800s throughout the 20th century, temperatures increased as atmospheric CO2 increased, but prior to 1860 atmospheric CO2 remained virtually constant while temperatures varied, up and down, including the medieval warm period and the little ice age.

If temperatures varied while atmospheric CO2 remained constant, there must not have been a very strong linkage between temperatures and atmospheric levels of CO2.

The Carrington event demonstrated the power of the sun, while Svensmark has shown how its power could affect climate change.

Couldn’t the sun be a more reasonable answer for climate change than atmospheric CO2?

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0 thoughts on “Sun Power, Part 2

  1. It is not the Earth’s magnetic field that deflects cosmic rays, but the solar field associated with the solar wind and SEP (charged particles) that flow out through the whole solar system. Cosmic ray particles (mostly ionized protons) have energies in the giga-volt range (a million times the energy of the solar wind, which does get deflected by Earth’s field), and to deflect cosmic ray particles requires either a very strong magnetic field or one that operates over a very large distance, such as the whole inter solar system. The Earth’s field is neither very strong nor does it extend sufficiently far.
    This does not change the possibility that cosmic ray particles may produce ionization in the atmosphere, which act as nuclei for cloud drops.

  2. Thanks.
    I have seen this explained in terms of solar flux and solar magnetic field. I can’t differentiate or explain which description is most accurate. The Earth’s magnetic field is a small player, though I don’t know how small.
    Can you send me a link to a better description of the mechanism i.e., magnetic field or solar wind, by which the cosmic rays are deflected or allowed to enter the Earth’s atmosphere?
    I want my description to be as accurate as possible.
    As best I can determine, the solar wind is a magnetized plasma.

  3. Here are two broad but general summary on cosmic rays.

    The solar wind is about 90% hydrogen and most of the rest helium. The nuclei are stripped of electrons, and thus the solar wind is a mixture of positive and negative particles, which behave differently in an electro-magnetic field. Because the propagated solar field is not linear, but distorted in shape, the altered particle path is not a smooth curve.

    The mechanism of deflection of cosmic rays is the same as what occurs in a laboratory mass spectrometer (you can google that for the basic physics). A particle is ionized and accelerated. When it passes through a magnetic field, its path is bent in proportion to its mass, but also in proportion to the strength of the magnetic field and the distance over which it exists. The solar field acts over most of the solar system, and very slowly produces significant alternation of the cosmic ray particle path, bending it out of the solar system. As cosmic ray particles have a distribution of energies, the lower energy ones are deflected more..

    • Thanks.
      The NASA article was very helpful. I already had a reasonably good understanding of cosmic rays, but the CalTech article helped broaden my understanding.

      I also read another paper, Solar Wind and Interplanetary Magnetic Field: A Tutorial by C.T. Russell. It was somewhat beyond my knowledge with respect to terminology and concepts, though the basic idea was clear.

      It described the solar wind as, “the solar wind is a magnetized plasma in which, throughout most of the solar system, the magnetic and plasma pressures are comparable.” The paper focuses on what transpires at 1AU, the distance from the sun to the Earth.

      The solar wind and accompanying magnetic field, forms the Heliosphere.

      NASA’s description of the three conditions that affect the heliosphere is very useful.
      1. The strength of sun’s magnetic field
      2. The strength of the solar wind
      3. The shape of the current sheet

      Anyone reading my article can see that the fundamental concept of the sun’s magnetic field blocking cosmic rays is abbreviated but sound.

      When I write on this subject again I will be clearer, and incorporate these three concepts into the article.

      My objective is to keep things simple, so that non-scientists/engineers can relate to the concepts, while being as accurate as possible when writing on any particular subject.

      And as you mentioned, the concept of cosmic rays affecting cloud cover remains a possibility.

      Thank you for your help.

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