Reprinted from Aeronautics and Astronautics, Vol. 13, No.4, pp. 10-19, April 1975, with the permission of the publisher, the American Institute for Aeronautics and Astronautics, and of the author. Sun-Weather Relationships
ByJ. W. KING Appleton Laboratory, Slough, England
As they profoundly influence civilization, and have not been well explored, Sun-weather relationships should become a major field of research in the decade being ushered in by GARP and the IMS
Many people have suggested in the past latitudes a negative correlation existed oscillations associated with the ll-year that the weather is influenced by the before about 1915 A.D. and a positive sunspot cycle exhibit opposite phases at 11- and 22-year sunspot cycles. I believe one after that. Bowen (1974) drew 17 deg Sand 43 deg S (see F-2). that the accumulated evidence is so attention to the fact that in the Moreover, the sunspot cycle appears to compelling that it is no longer possible southern hemisphere the rainfall influence the rainfall in opposite ways to deny the existence of strong con- at 55 deg Nand 35 deg N (King, 1973). nections between the weather and The solar-cycle-induced rainfall radiation changes (electromagnetic oscillations referred to range from and/or corpuscular) associated with 'I about 3 to some 50% of the normal whole range of solar phenomena. Eve" annual total. Obviously, a reduction of the most skeptical scientist who in- rainfall by 25% in each of several years vestigates the literature thoroughly will around one of the extremes of the be forced to concede that important sunspot cycle is of considerable im- aspects of lower-atmosphere behavior portance. .Anillyses comb in in data are associated with solar phenomena ~ zones exhibiting opposite solar- ranging from short-lived events such as cycle effects will inevitably lead to the solar flares, through 27-day solar erroneous conclusion that no solar- rotations to the l I-year, 22-year, and cycle effect exists, as will an ana ySIS of even longer solar cycles. The com- rainfall data from regions situated plicated pattern of sun-weather between zones in which the sunspot- relationships undoubtedly needs much cycle effect is opposite. further clarification, but progress in The annual rainfall totals at For- this field will be hindered if the view taleza, Brazil, and at three sites in prevails that such relationships should South Africa (F-3 and F-4) were not be taken seriously simply because positively correlated with the "double" the mechanisms involved in explaining JOE W. KING received a Ph.D. at sunspot cycle for considerable periods Cambridge University, England, in them are not yet identified. 1955 and was awarded the of time. The modulation associated What must be sought now are the Hamilton Prize by the University with the double cycle amounted to mechanisms responsible for the for his dissertation. He is an about 35% of the average annual total complicated sun-weather relationships "individual merit senior principal at Fortaleza and to about 25% of the scientific officer" at the Appleton that exist and greater insight into their Laboratory. At Appleton he average rainfall at the South African practical consequences for agriculture, received the 1966 Wolfe Award stations. Data from Fortaleza are energy consumption, and national from the U.K. Ministry of Technol- available from 1865 onwards. After the economies. ogy for his upper-atmospheric first 60 years the relationship between research. For four years Dr. King chaired the European Space the rainfall and the double cycle at Weather and the Solar Cycle Research Organisation's ion group Fortaleza changed phase. The SO years F-l summarizes a rainfall analysis by and is now vice-president of the of data available from South Africa ICSU special committee on solar- show a consistent positive correlation Xanthakis (1973). He observed that at terrestrial physics and chairman- high northern latitudes (70-80 deg) the elect of the URSI commission on with the double cycle. The African ll-year solar cycle was positively the ionosphere. He is a member of rainfall data for latitudes south of those correlated with a lO-cm oscillation in three British national committees where the double-sunspot-cycle in- the annual rainfall total; at latitudes (for radio science, geomagnetism fluence is observed exhibit a and aeronomy and solar-terrestrial between 60 and 70 deg N the opposite physics). pronounced oscillation having a period behavior occurred while at still lower of about 10 years (Tyson et al, 1974) in 109 anti-phase with the sunspot cycle (King 25070"· BO° N 157"W-srE et al, 1974). U)200 12 STATI F-5 gives particularly impressive ~ evidence of an association between :f 150 rainfall and the double sunspot cycle. It !z 100
200 A FORTALEZA (4°S.39°W) E 0::: 100 w B CD :2 ::::J Z 0::: 100 I- 0 w o0.. CD :2 (f) ::::J Z Z ::::J (f)-IOO ~ (f) tSUNSPOTi Z I MINIMA ::::J r i r (f) -100 -2001~9~10~~B~20~~19~3~0~~19~4~0--~19~5~0---1~9L60--~1970 YEAR AD. r r I i F-4 Smoothed annual rainfall totals at three places in -2°98~6~5~~1~87=5~~18~8~5--~18~9~5---=19~0~5--~B~15~--~19South25 Africa (after Tyson, 1974) compared with the double sunspot cycle; the period studied includes six sunspot YEAR AD minima. regions, the mean air temperature at 2. The level of the water in Lake or some other solar phenomenon the Earth's surface varies in opposition Victoria, positively correlated with associated with sunspots cause to the sunspot cycle, being lowest at sunspot number before about 1930, has thunderstorms." They also established sunspot maxima and highest at sunspot been negatively correlated since about statistically that the observed variation minima. This was suspected by Her- 1950; during the interim period little of the frequency of thunderstorms in schel as early as 1801 but was first correlation existed between sunspot the West Indies during the sunspot clearly demonstrated by Koppen (1873) number and the water level. cycle was "definitely significant," the and has since been confirmed by Lightning events in Great Britain (F- probability of obtaining the correlation Mielke (1913), Hildebrandsson (1914), 7, plotted on an arbitrary scale by chance being less than 0.1% "We Walker (1915, 1923), Mecking (1918), designed to indicate variations in the have established," they said, "a high Clayton (1923), Droste (1924) and number of power failures associated probability that thunderstorm others." In their Handbook of with lightning strikes) during four frequency ill the West Indies is related Statistical Methods. in Meteorology, sunspot cycles varied by a factor of in some way to the sunspot maximum." Brooks and Carruthers (1953) nearly two in phase with the sunspot Cornish (1954) concluded that the examined the significance of some of cycle (Stringfellow, 1974). Brooks oscillations in the Adelaide rainfall the negative correlations between (1934) first showed that a significant records (F ·5), "must be due to secular tropical temperatures and sunspot relationship exists between the oc- changes in the latitudinal paths of numbers and concluded that they were currence of thunderstorms and the anticyclones with their attendant "undoubtedly significant." Although annual sunspot numbers: correlation cyclones across southern Australia." the tropical temperatures examined by coefficients up to 0.91 were obtained Bodurtha (1952) reported that the the early workers referred to by Brooks from long series of data, the largest sunspot cycle strongly influences both correlated negatively with sunspot correlation coefficients relating to high the frequency and the intensity of number, Troup (1962) pointed out a latitudes. In 1953 Brooks and anticyclogenesis, so it may be con- relatively recent reversal of this: "Over Carruthers made this observation: cluded that the number and intensity of the tropics as a whole, the correlations "There is a correlation coefficient of + anticyclones and the latitudes at which between sunspot number and tropical 0.88 between the number of thun- they occur all vary during the solar temperatures which were negative prior derstorms recorded in Siberia and cycle. to 1920 have become zero or even mean annual sunspot relative number. Schostakowitsch made one of the positive subsequently. Of recent years Since it 'is inconceivable that thun- most comprehensive investigations of there has apparently been a reversal in derstorms in Siberia cause sunspots, it the influence of the solar cycle on the the phase of the temperature cycle." is reasonable to assume that sunspots weather. He prepared detailed global III F-5 Ten-year smoothed means (lower curve) of the annual rainfall "quartile" (the o date by which one quarter of APRIIr------~ the annual rai nfall had oc- curred) for Adelaide, APR21 Australia. After Cornish (1954). The date fl uctuates by MAY I about six weeks in phase with the double sunspot cycle MAYII plotted in the form shown in the upper curve. The Cornish MAY 21 data points are sl ightly displaced because he used MAY 31 smoothed means for an even number of years. JUNIOL---~---L--~----L----L--~----L---~---L--~ 1844 1854 1864 1874 1884 1894 1904 1914 1924 1934 1944 YEAR A.D. CENTRAL ENGLAND. JULY ~ 16·5 ~ w jI20,------.------.--- a:: w ::J LL tr 2 a:: '" w a: (L l;; ::;; 0: w w r l- LL 15,5 :'!IOO x 0: w W a ::CD;, ;;; :::J w 1002 \;! I- l( ~ maps '(reproduced by Clayton, 1933) flares, Schuurmans (1965) computed zone." Reiter (1973) showed that the showing how the temperature, pressure the change in height of the SOO-mb level influx of stratospheric air to the 3-km and rainfall over the Earth vary be- over much of the northern hemisphere level increases on the second or third tween sunspot minimum and during the first 24 hr after each of 53 day after an H 0: and/or X-ray flare. He maximum. flares. He concluded that the pattern of concluded that "the use of this height changes "shows a remarkable statistically evident solar-terrestrial Response of the Lower Atmosphere regularity with a symmetry with respect relationship would be in order in the To Short-Lived Solar Phenomena to the geomagnetic rather than to the practical forecasting of influxes of In recent years, several analyses have geographic pole. The main features stratospheric air into the biosphere." indicated that short-lived solar suggested by the picture are a rise in Results such as these show that the phenomena may trigger a response in height in the region of the geomagnetic circulation of the lower atmosphere is the lower atmosphere. To investigate pole and a wide region of fall in height significantly modified after solar flares. the tropospheric response to solar coinciding quite well with the auroral As measured by the "vorticity area 112 120~--~-----.-----.----,-----,----, not related to" the Moon. Studies of the phase of the cycle suggest that, if the /", POLARITY CHANG1-.:..:... periodicity has a solar origin, its phase must be determined by another 115 / ' __ ?-::-:.77-.L::.····...TOWARDS-A. WAY1/ "'~ -, / /- ....FROM SUN(24)/ .: ,'::.,. mechanism. Berkes (1955) has reported the existence of a 27-day periodicity in ..' / \-I, /.: v- wind speed and Egyed (1961) noted a 110 ·········P~LARITY \ '\. /./ 27-day periodicity in soil temperature. Many authors including Sazonov C\J CHANGE AWAY \... / . FROM - TOWARDS', \. /. . (1%5), Mustel (1%6), Beynon and E Winstanley (1969), Roberts and Olson .x: SUN (29) ':::·~f ID (1973), Stolov and Shapiro (1974), and o Sidorenkov (1974) have reported 16JAN- 31 MAR (22) associations between magnetic activity X :--...... •... ..••.\ . 115 V j\ -, I.... -, . and lower atmospheric phenomena. But Hines (1973) pointed out that, since x :'\ /\ \ I.: \ w ....' \_1 '- j .... j / , geomagnetic activity may be caused by o 110 /\. \ /.... <, lower-atmosphere disturbances, it is Z not possible to come to any definite I NOV - 15JAM3IJ···.....~ - 1967 - 1970 (27) I- r- it may be significant that at least some U " ---.. I .~ -, of the atmospheric phenomena occur i= ····7 ...:.:../····.-:..\ ········ / ..: " . several days after the associated 0:: \ / -, . geomagnetic activity. For example, F-9 o - / /. shows that the vorticity area index for > 110 .o 1964-1966 (26) """ troughs preceded by a sharp rise in r' magnetic activity increases 40% five E ,. ..."/., o ••.••• I days after the magnetic disturbance. o 105 ...... :."/ This behaviour, and some of the r0 , .... / y/ other s un-weat her relationships mentioned, occurs only during winter 100~----~----~--~-----L-----L----~ months. Stolov and Shapiro (1974) -4 -2 0 2 4 6 analysed 24 years of 700·mb heights -6 from 200N to 700N and concluded that DAYS AFTER CROSSING SECTOR BOUNDARY "the 7oo·mb height difference between F-B Average behaviour of the northern-hemisphere "vorticity area index" around 200N and 550N increases significantly the dates of 53 interplanetary-magnetic-tield sector boundary crossings; winter, in winter four days following 1964-70. The data have been divided into two groups in three different ways. In geomagnetic disturbance." Even in each case, the hem ispheric vorticity index shows an oscillation of about 10%. After Wilcox et al (1974). summer a statistically significant in- crease was found, but "the effect is most clear in: winter in the quadrant index" at various heights in the al (1974) have also reported a 900 to 1750W and corresponds to a 7% troposphere (Wilcox et al, 1974), the relationship between sector crossings increase in the mean geostrophic circulation also appears to be modified and the lower atmosphere. westerly flow." Their analysis of the around times when the interplanetary Solar phenomena tend to recur with 700·mb heights following geomagnetic magnetic field sector boundaries cross periods of the order of 27 days, the disturbances reveals that "the effect the Earth. These boundaries originate synodic period of revolution of the Sun. proceeds with the growth and at the Sun and sweep across the Earth Panofsky (1967) has shown that "this development of large negative centres as they rotate during the 27-day solar period is close to the period of the in the latitude belt 400N to 600N." rotation. F-8 shows how the vorticity maximum fluctuations of mean west Role of Earth's area index of the northern hemisphere winds" at upper-middle latitudes. Magnetic Field varied on average during the 53 sector Similar behaviour is not observed at boundary crossings for which dates lower latitudes. Several studies have shown that sun- were known. It appears significant that After an investigation of the 5OO-mb weather relationships are most sim ilar results were obtained circulation along the auroral belt, Riehl pronounced in the vicinity of the irrespective of how the data set was (1956) concluded that "circulation auroral zone. Sarukhanyan and subdivided: Three different methods increases and decreases take place with Smirnov (1970), for example, concluded (see F-8) each showed the average a period which can be related to the "the pattern of the amplitude vorticity area index varying by about mean solar rotation in the (solar) distribution of the l l-year variation of 10%. A change of this magnitude in the equatorial zone." atmospheric pressure shows that the index is of considerable importance. Rosenberg and Coleman (1974) amplitude increases only up to 700N. Because only limited data are available studied the southern California rainfall Further north the amplitudes decrease. at the present time, further information power spectrum and concluded that Thus the maximum amplitudes of the about the behaviour of the troposphere "there is a significant peak at almost l l-year variations are observed in the during sector boundary crossings will exactly 27.0 days." Their study showed 65- 700N zone. This zone is known to be awaited with interest. Mansurov et that the 27-day rain cycle is "probably have the maximum density of solar 113 corpuscular radiation, maximum 13~----~----~----~----~--~ occurrence of auroras, and maximum frequency of magnetic disturbances." F-lO shows the latitudinal variation 94 TROUGHS A of the change in surface pressure (averaged around the Earth at par- 120 PRECEDED BY / \ ticular latitudes) between sunspot SHARP RISE IN (/ \ minimum and maximum. calculated by MAGNETIC \ me from data published by Miles N (1974). The pressure variation E .x associated with the ll-year sunspot v 110 A~TIVITY~/ \ cycle is particularly large in the auroral o belt. (Unfortunately, Miles did not x publish data for higher latitudes.) The x observation of Sarukhanyan and w / L_, Smimov-that the effect decreases at o 100 Z \ latitudes above 700N-has been /' 114 800,--,--,---,--,--,---,--,---,--, 600 400 200 AURORAL ---.BELT 0-6 0-4 0-2 LONGITUDE (OE) 00 30 60 90 F-11 Spatial variations of three different meteorological parameters compared with the intensity of the LATITUDE (ON) geomagnetic field (after King, 1974b)_ The upper three F-10 Latitudinal variations of two atmospheric boxes contain maps, published by Bean et al (1966), that parameters showing particularly large effects in the indicate how average tropospheric temperature, surface auroral belt. The val ues in the upper and lower curves were humidity and surface pressure vary over most of the calculated from data published by Van Loon et al (1973) northern hemisphere in November. The lowest box and Miles (1974) respectively. contains a map of the intensity of Earth's magnetic field. 540.-----~------~----~~----~------,------...... (f) 500 m bar (shifted f- 25°to the West) -49 z (f) => 0:: Magnetic u) W f- 0 w -51 U 2 530 <:( 0 U -l w w 0 -53 LL U -l f= w > -55 zw w 520 l') -l <:( .D 2 E -57 (f) 0 :r: 0 f- LD 0:: LL <:( 0 -59 w f- 510 LL :r: 0 l') >- -61 f- F-12 Longitudinal W :r: (7j variations at 60-deg N of z the average height of the w 500-mb level for January f- (after Palmen and Newton, -63 z 1969) shifted 25 deg to the 500 west and the intensity of -180 -120 -60 0 60 120 180 the geomagnetic field. LONGITUDE (DEGREES EAST) 115 correlation coefficient between pairs of present time we know that large as a consequence of this, the field may values read off the two curves at in- changes in the amount of ozone may influence the weather. It should be tervals of SO,OOO years is 0.67, in- take place within a few days-changes borne in mind that "the correlation dicating a very high probability (greater of the order of±2S%-and these are coefficient between the temperature of than 99.9%) that the two parameters closely associated with changes in the the troposphere and the ozone content are related. King and Willis (1974) have weather conditions." of the atmosphere is about -0.7" suggested that the "Little Ice Age" The spatial variation of ozone over (Dobson, 1936). which occurred in Europe between the Earth is not yet fully understood, Apart from cosmic rays and ozone, 15SO and 1850 A.D. was associated and it seems reasonable to suggest that other mechanisms which may affect with the unusually high values of attention should be paid to the Sun-weather relationships include the magnetic inclination that existed at remarkable similarity which exists following: that time. between the global map of ozone and 1. The influence of energetically the intensity of the geomagnetic field. weak upper-atmosphere phenomena on Mechanisms F-15 shows the regions where most lower-atmosphere systems that are The Earth's magnetic field, as we ozone is observed in the northern and close to resonance (Green, 1974). The see, may playa role in bringing some southern hemispheres (London and effective amplification (of an sun-weather relationships about. What Kelley, 1974), and I have compared energetically weak driving force) that geophysical phenomena that vary these with the regions of extreme may occur in an atmosphere which during the solar cycle, we might then magnetic Band L values. It may be that reacts nonlinearly has not yet been ask, does the Earth's magnetic field the ozone content is controlled in some adequately investigated. influence? way by the Earth's magnetic field and, 2. The solar-cycle variation of the One is cosmic rays. Ney (1959) drew attention to the fact that at the 500-mb level the amount of ionization 47.600r---r----.---,--,--r---r---,---,--,--,----,---,--y---,4·8 U associated with cosmic rays decreases 47.800 4'6 ~ by a factor of about 4 between sunspot ~ 48.000 4'4 gs minimum and maximum, and made ~ ~ this suggestion: "If there is a con- ~ 48.200 4'2 a:: ~ w nection between atmospheric ionization ~ 48.400 4'0 ~ and thunderstorm activity for example, ~ 48,600 3'8 ~ iJi a solar-cycle modulation might be z observed in climatological data." The w Ui effects of the sunspot-cycle-induced ~ 47,600 w I changes of lower-atmosphere con- u 47,700 U i= ~ ductivity on atmospheric electric fields, ~ 47,800 ...J cloud formation, tem peratures, ~ 47,900 ~ thunderstorm activity and rainfall do ~ z 48,000 116 F-15 OZONE AND MAGNETIC-FIELD VALUES frequency of occurrence of short-lived The upper box .shows the regions in the northern and southern hemispheres phenomena. The response of the where the total ozone content, averaged over 13 years, is greatest. The ozone troposphere to the ll-year sunspot content decreases from the high values shown to about 240 m illiatmosphere centimetres at low latitudes. After London and Kelley, (1974). The lower box cycle may represent merely an in- shows the regions of greatest magnetic-B and magnetic-L values in each tegration of the effects caused by short- hemisphere. lived phenomena such as solar flares or 90.------~------~------~------.geomagnetic storms, which are much more frequent at sunspot maximum 6 than minimum. 3. The effect of water vapour formed from solar-wind protons as suggested 30 by de Turville (1%la, 1961 b). 4. The effects of possible, but as yet o unknown, solar-cycle changes in the "Solar Constant," that is, in the total electromagnetic energy radiated by the -30 320 Sun. 340 -60 S. Variations of the efficiency of the -:;'2-0 C > coupling between the solar wind and .e.....z the magnetosphere as the direction of the interplanetary magnetic field varies w (Svalgaard and Wilcox, 1974) or as the o::J 60 solar-wind velocity varies (Intriligator, r- 1974) during the sunspot cycle. ~ 30 B=O'50 6. Variable reflection by the upper -.J atmosphere of upward-propagating o gravity-wave energy (Hines, 1974). Implications of Sun- Weather -30 Relationships Sun-weather relationships affect our -60 &~o.ss lives in numerous ways, many of which are not appreciated. The following are -90~------~------L------~------~ examples: -180 -90 0 90 180 Energy budgeting and electricity LONGITUDE (OE) distribution. Mather (1974) has shown that between 1900 and 1960 in Maryland, Delaware, and Virginia 60,------,------,------, temperature oscillations averaging 2.S C (4.S F) occurred with "a marked cyclic movement with about 22 years between success ive peaks." These oscillations are 180 deg out of phase with the double sunspot cycle plotted in F-S, and there seems little doubt that they are associated with the double cycle. A 2.S C temperature oscillation extending over large areas will ob- viously affect the demand for energy. It should be noted in this connection that the frequency of lightning strikes af- fecting electricity supplies (F -7) correlates strongly with the sunspot cycle in certain parts ofthe world. Food production and famines. Several authors have drawn attention to the influence of the sunspot cycle on agricultural productivity; relationships between the solar cycle and agriculture are hardly surprising since the phase of the annual rainfall can vary by six weeks during the double solar cycle (F- S). Filewicz (1962) discussed the effects 1875 1900 1925 of severe winters on fruit-growing in YEAR A.D. North America and Europe. He and F-16 Evidence from which Vibe (1967) concluded that the sunspot cycle in- others (particularly Baur-see Lamb, fluences the motion of sea ice around Greenland. 1972) believe severe winters to be 117 associated with the extremes of the It is interesting that famines, which resolve several problems in the field of sunspot cycle. After a study of forest occur mainly in the eastern half of the sun-weather relations, including the growth, Bray (1965) saw a "relationship northern hemisphere around sunspot following: between growing season, climate and minimum, tend to migrate northward. -How does the efficiency of the solar activity." I have shown (King. Famine swept China in the periods coupling between the solar wind and 1973) that the length of the growing 1887-89,1919-21 and 1929-30 and then the magnetosphere vary during the season estimated for 'agricultural in Russia in 1891-92, 1921-22 and sunspot cycle? purposes varies in phase with the 1932-33. This northward migration of -What physical phenomena ac- sunspot cycle. King et al (1974) used the famine regions resembles the company interplanetary magnetic field world wheat-production figures for movement of drought regions in North sector boundaries? 1949-73 to show how the sunspot cycle America. As Thompson (1973) points -How constant is the Solar Constant? influences food production and con- out, "The droughts of the 1930s and -What properties of the 22-year cluded that the present low level of 1950s began in the southwestern states sunspot cycle may be associated with world food reserves may be associated several years before the peak of the lower-atmosphere effects? with the decline in solar activity during droughts in Nebraska and Kansas. The All the "mechanisms" described the approach to the 1974-75 sunspot tendency apparently is for droughts to earlier require further study to minimum. The modulation of wheat migrate northward gradually for determine whether or not they playa production associated with the l l-year several years." role in sun-weather relationships. It sunspot cycle seems to be at least 100/0 Drift of sea ice. The upper part of F- appears unlikely that significant in many parts of the world; in certain 16 contains information kindly drawn progress will be made in this field until countries it may even exceed 50%. to my attention by E. Ungstrup. The we know the general morphology of the The decline of solar activity between curve shows the "polar-bear bag" in Sun-weather relationships that exist the 1968 sunspot maximum and the southwest Greenland-the number of and the role played in these by the minimum due in about 1974 may well polar bears caught there each year auroral zone. We need further com- account for the shortfalls of the Soviet (Vibe, 1967). Vibe, a zoologist, pointed parisons of geomagnetic and wheat crops in recent years. out that the polar bear bag follows the climatological data from different Thompson (1973) and Roberts (1974) sunspot cycle (delayed, as F-16 shows, epochs to establish the relationships drew attention to the fact that droughts by about two years). He says that the between magnetic-field and climatic in certain agriculturally important sunspot cycle appears to "influence the changes. regions of the United States occur in acceleration of drift ice which serves the It appears highly desirable that the the years around every second sunspot polar bear as a means of trans- effects of geophysical phenomena minimum. The last drought was portation." If Vibe's interpretation is should be included somehow in centered on the sunspot-minimum year correct, the solar cycle exerts a meteorological models. If, for example, of 1954, and it seems significant that significant influence on the behaviour the wavenumber 1 and wavenumber 2 the wheat crop in the United States in of sea ice in the north Atlantic. The tropospheric patterns are associated that year fell 12% short of the average possible implications of this for nor- with Earth's magnetic field, they for the five previous years. In 1974, thern countries and also for the science should probably not be expected to when the next drought was to be ex- of oceanography .and the theory of move as though they were Rossby pected, lack of rain adversely affected ocean-atmosphere coupling should be waves. The accuracy of calculations the U.S. corn crop. assessed. made using divergent barotropic Further examples of solar-cycle Inadvertent man-made weather models could perhaps be improved by effects on agriculture have been cited modification. Helliwell and Katsufrakis making allowance for certain by Gamow (1965): "The correlation (1974) reported that the Canadian geophysical processes. between the number of sunspots and electrical power d istribu tion system The coincidence of major in- the growth of trees indicates that trees appears to trigger VLF emissions in the ternational meteorological and grow faster during the years of sunspot magnetosphere. Such emissions induce geophysical programs, the Global maxima. A related correlation seems to electron precipitation, and if particle Atmospheric Research Program exist between the number of sunspots events do indeed affect the circulation (GARP) and the International and the price of wheat: the smaller the of the troposphere, a real possibility Magnetospheric Study OMS), later in number of sunspots, the higher the exists that electricity distribution this decade provides a golden op- price of wheat. This can probably be systems may influence the lower at- portunity for collaboration between two explained by saying that during the mosphere. groups of scientists who must surely lean sunspot years less wheat grows per National economic systems. Several interact more than they do at present- acre." authors have gone so far as to suggest meteorologists and space physicists. In a recent analysis (to be published that solar-cycle-induced meteorological Acknowledgment elsewhere), I show that 29 of the 68 effects may be sufficiently important to major famines since 1700 A.D. came in influence the economies of in- I owe thanks to J. A. Saxton, sunspot-minimum years or in the years dustrialized nations. A review of this Director of the Appleton Laboratory, immed iately preceding sunspot subject has been published by Williams for supporting this work, and I am minimum. The probability of such a (1961). Sparkes (1974) supports the indebted to Mrs. A. 1. Slater for help high proportion of the famines oc- opinion of the economist J. M. Keynes with data analysis. curring by chance in these two years (1961). The possibility of solar-cycle- References from each sunspot cycle is smaller than induced meteorological phenomena 10-4. Of the ten "sunspot minimum playing a part in harvest fluctuations Full details of the papers referred to minus one" years during the period which in turn affect the trade cycle, can be obtained from me on request. 1866 to 1963, eight produced famines concluded Keynes, "is not to be lightly Please use the following address: Dr. J. killing a total of at least 26 million dismissed." W. King, Appleton Laboratory, Ditton people. It will take satellite observations to Park, Slough SL3 9JX, England. • 118