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The Impact of Variable Solar Activity on Earth's Climate
Volume 8, Number 1: 5 January 2005

There were periods in the past, according to Pustilnik and Yom Din (2004), "when numerous enthusiasts accepted the influence of solar activity on the terrestrial environment as an evident fact."  Throughout the 20th century, however, a more agnostic view prevailed, the outlines of which are briefly described in our review of the paper of Damon and Laut (2004), which illuminates the most recent incarnation of the clash of the two philosophies, where emphasis is currently placed on making a direct, albeit multiple-linked, connection between observable climatic parameters and measurable characteristics of solar activity.  With the seeming deadlock that prevails in this enterprise, however, it is only natural to wonder if there is another way of attacking the problem that could skirt, at least in the short term, this significant impasse.

One promising approach is the tack being taken by Pustilnik and Yom Din (2003, 2004), who have looked for links between solar activity and the market prices of various consumables (such as wheat) - which are known to be influenced by climate via the effect of climate on yield - by analyzing the characteristics of cycles that can be demonstrated to exist in temporal displays of each factor.

In their first foray into this field of climatic sleuthing, Pustilnik and Yom Din (2003) compared statistical properties of the intervals between wheat price bursts in England during the period AD 1249-1703 with the statistical properties of intervals between minimums of solar cycles during the period 1700-2000.  In doing so, they found, in their words, that "statistical properties of these two samples are similar, both for characteristics of the distributions and for histograms of the distributions."  In addition, they analyzed the direct link between wheat prices and solar activity in the 17th century, finding that "for all 10 time moments of the solar activity minimums the observed prices were higher than prices for the correspondent time moments of maximal solar activity (100% sign correlation, on a significance level < 0.2%)."  These two sets of results were considered by them - and rightly so, in our opinion - to represent "direct evidence of the causal connection between wheat price bursts and solar activity," which in turn suggests that variable solar activity does indeed influence earth's climate.

So just what is this causal connection of which Pustilnik and Yom Din write?  In a nutshell, it is currently postulated to begin with the cyclical variability of solar magnetic activity, which cyclically modulates the solar wind, which similarly modulates the galactic cosmic ray flux that is ever incident upon the earth, which likewise affects cloud climatology, which in the proper solar activity phase can lead to a drop in agricultural production, which in turn leads to "price bursts" that result from reduced consumable availability, such as reduced wheat yields.

In their second attempt to demonstrate the reality of a solar-agricultural connection, Pustilnik and Yom Din (2004) studied the cyclical behavior of the Composite Unit of Consumables in England for the period AD 1264-1954, as well as the average yearly prices of various types of wheat grown in the United States over the 20th century.  The first of these exercises, i.e., their "test of the interval distribution of the prices of consumables for Medieval England," once again revealed "a good consistence with the interval distribution of sunspot minimum-minimum."  Likewise, the second endeavor, i.e., their "test of the maximum-minimum price asymmetry for wheat in the USA in the 20th century," showed that "the effect of the influence of solar activity also occurred," although its amplitude and significance were lower than what they found for Medieval England, presumably as a result of the confounding effects of the existence of reserves and access to external markets with low transfer costs in the 20th century (both of which phenomena were minor to non-existent in Medieval England), which tend to suppress market sensitivity to disturbances of local product supply.

The several results obtained by Pustilnik and Yom Din clearly suggest there is a solar-climate connection that is much stronger than what is implied by the small change in solar irradiance that is evident in the 11-year solar cycle.  Hence, it behooves us to continue to work on the problem of quantitatively elucidating the several linkages in the proposed chain of events that begins with a change in solar activity and ends with a change in the price of agricultural consumables.  In so doing, we should eventually gain a full understanding the several phenomena that combine to produce the linkages that lead from changes in solar activity to the changes in climate that produce observable changes in crop productivity.

Sherwood, Keith and Craig Idso

References
Damon, P.E. and Laut, P.  2004.  Pattern of strange errors plagues solar activity and terrestrial climatic data.  EOS, Transactions, American Geophysical Union 85: 370, 374.

Pustilnik, L.A. and Yom Din, G.  2003.  Influence of solar activity on state of wheat market in medieval England.  Proceedings of International Cosmic Ray Conference.

Pustilnik, L.A. and Yom Din, G.  2004.  Space climate manifestation in earth prices - from medieval England up to modern USA.  First International Symposium on Space Climate: Direct and Indirect Observations of Long-Term Solar Activity.