August 20, 2004
Variations In Sun's Magnetic Field Influence Climate Trends?

Some climate scientists are arguing that the intensity of cosmic rays from distant exploding stars varies over time to cause long term changes in Earth's climate.

The idea will also be backed up by Nigel Marsh of the Danish Space Research Institute in Copenhagen.

Marsh and his colleagues looked at satellite images of low-altitude clouds from the past 20 years. They noticed that the pattern of global cloud cover varied over a time scale of roughly 10 years, and found a correlation with the 11-year sunspot cycle.

The more sunspot activity there is, the greater the strength of the sun's magnetic field. And cosmic rays are deflected by this field, so the stronger it is, the fewer rays reach the Earth, and the lower the cloud cover.

The Copenhagen team also found that clouds were scarce near the equator and thicker towards the tropics. According to Marsh, this is because cosmic rays have a hard time punching through Earth's magnetic field at the equator, but can leak in through the relatively weaker field nearer the poles.

The Sun is known to go through periods of much lower sunspot activity. One such period is known as the Maunder Minimum coincided with the "Little Ice Age" back in 1645-1715. During low sunspot periods it is thought that the Sun puts out less light energy and hence causes a cooling effect on Earth's climate. But this theory about cosmic rays basically provides another way that sunspot activity fluctuations can cause climate fluctuations: low sunspot activity reduces the magnetic field of the sun and therefore lets more cosmic rays through to the Earth to increase cloud cover and therefore to cause reflection of light before it reaches the surface.

One of the proponents of this theory, Nir Shaviv of the Hebrew University in Jerusalem, Israel has an interesting set of web pages arguing his view point. See his graph of Earth climate cycles and Milky Way galaxy spiral arm rotations.

There are indications that Cosmic Rays affect climate on Earth. If this is true, then one should expect climatic variations while we roam the galaxy. This is because the density of cosmic ray sources in the galaxy is not uniform. In fact, it is concentrated in the galactic spiral arms (it arises from supernovae, which in our galaxy arise predominantly from the death of massive stars, which in turn form and die predominantly in spiral arms). Thus, each time we cross a galactic arm, we should expect a colder climate. Current data for the spiral arm passages gives a crossing once every 135+/-25 Million years.

A record of the long term variations of the galactic cosmic ray flux can be extracted from Iron meteorites. It was found in this work that the cosmic ray flux varied periodically (with flux variations greater than a factor of 2.5) with an average period of 143 +/- 10 Million years. This is consistent with the expected spiral arm crossing period and with the picture that the cosmic ray flux should be variable. The agreement is also with the correct phase.

The main result of this research, is that the variations of the flux, as predicted from the galactic model and as observed from the Iron meteorites is in sync with the occurrence of ice-age epochs on Earth. The agreement is both in period and in phase: (1) The observed period of the occurrence of ice-age epochs on Earth is 145+/-10 Myr (compared with 143 +/- 10 Myrs for the Cosmic ray flux variations), (2) The mid point of the ice-age epochs is predicted to lag by 31 +/- 8 Myr and observed to lag by 33 +/- 20 Myr. This can be seen in the following graph:

I am in no way qualified to comment on the plausibility of this particular theory. But there have been a number of surprising discoveries in recent years of unexpected factors that influence climate (see my Trends Climate category archives for interesting examples). This leads me to suspect that current climate models are too simple to use with a high level of confidence when making public policy decisions. There is a large degree of uncertainty when we look ahead at the future of Earth's climate.

Share |      Randall Parker, 2004 August 20 03:42 PM  Climate Trends

willie soon said at August 25, 2004 6:55 AM:

hi randall,

just saw your posting through TechCentralStation (i post
articles occasionally,

i simply want to add to your reading by making
available good reading on the subject of Maunder Minimum and
Sun-Climate connection:

(1) "The Maunder Minimum and the Variable Sun-Earth Connection"
(Soon & Yaskell, World Scientific Publishing Co, 2004)
for a popular and accessible reading of the subject

(2) Summer_of_1816.pdf (6.6 Mb) from

The 1816 article contains descriptions of the cold 1816 summer (yes
that meant June's icicles and August's snow in New England!),
the April 1815's Tambora eruption, the Dalton minimum of
the solar magnetic activity cycles, the wobbling position of
the Sun in the solar system, Mary Shelley's Frankenstein, Ben Franklin's
note on the association of volcanic eruptions/ejecta and foul weather.

Also Thomas Jefferson's weather record at Montecello plus his remarkable
foresights to call for the establishment of a modern paleoclimatic
reconstruction program "to ascertain ... curious [weather/climate] fact
in physical history" and more!

(3) you and other interested readers may also find several
papers on the subject of CO2 and global warming and the
difficult implementatons in compute climate models in
the same URL posted above for 1816.

I recommend
(a) CRpaperACTUALNov01.pdf

(b) Apr7-EnEpaper+3figures.pdf

(c) SLB-GRL04-NHtempTrend.pdf

Of course, please feel free to read anything on this URL,
probably the most important and interesting documents
are my replies to questions from US Senators
in Soon-replytoInhofe.pdf + Soon-replytoJefford.pdf

thanks again for the discussion and especially for calling attention
to closer attention to solar variability as plausible and non-negligible
factors of past, present and future change in earth's climate.

good day!


Willie Soon
Harvard-Smithsonian Center for Astrophysics
60 Garden Street, MS 16
Cambridge, MA 02138, USA
phone: (617) 495-7488
fax : (617) 495-7095

Author of the new book: "The Maunder Minimum and the Variable
Sun-Earth Connection" (March 2004)

Also the Receiving Editor for New Astronomy

"He had been Eight Years upon a Project
for extracting Sun Beams out of Cucumbers,
which were to be put into Vials hermetically
sealed, and let out to warm the Air in the raw
inclement Summers."
--- (A visit to the grand Academy of Lagado, Swift 1726)

Steve Yaskell said at September 2, 2004 2:53 AM:

Dear Randall,

The latest rampages, I read, up on Capitol Hill with Baliunas and Soon and Mann (read Legates' commentary in the Washington Post of Aug 26, last, reachable on the web) are a series of events that stretch out past the several years I spent working on various projects with Dr. Soon.

I think it goes all the way back to Ecclesiastes, in Chap 9, 13-18:

"This wisdom have I seen also under the sun, and it seemed great unto me.

There was a little city, and few men within it, and there came a great king against it,
and besieged it, and built great bulwarks against it.

Now there was found in it a poor wise man, and he by his wisdom delivered (saved) the city:
Yet no poor man remembered that same wise poor man.

Then I said, Wisdom is better than strength: nevertheless the poor man's wisdom is despised,
and his words are not heard.

The words of wise men ARE heard in quiet more than the cry of him that ruleth among fools."

But the preacher concludes Chapter 9 thus,

"Wisdom is better tha weapons of war: but one sinner destroyeth much good."

So the moral of the story is, the levite (poor, wise) protects and saves the truth (Lincoln comes to
mind, and his war on slavery). But the lesson is, that it only takes one to destroy the good (the truth,
human happiness, maybe lives etc.)

(I think of the ancient Swedish diplomat (who died of illness in the Maunder Minimum) Axel Oxensjärnas's famous words, as he instructed his son in the diplomatic arts; "behold, with what little wisdom is the world guided."

There are, if you read the papers, many loud cries ringing out among those who rule loudly.

I take faith in the belief that in the quiet, the wise are heard (and I am no regular church goer or evangelist). But of course, having simply quoted some Judeo-Christian scripture, I have labeled myself an outcast among the loud: perhaps even a pervert.

best regards,

Steve Yaskell

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