The La Porte Weather Anomaly: ItsControversies and Implications

Val EichenlaubDepartment of Geography, Western Michigan University,

Kalamazoo, Michigan 49001

The fact that cities affect climates in various ways and thatinadvertent climatic change has resulted from the progressive con-centration of people and their activities in urban areas has long beenrecognized. Increasing stress on finely-tuned atmospheric systems bymetropolitan areas seems likely in the future since the trend of urbangrowth continues unabated; the 1970 XL S. Census shows nearly theentire decadal growth of population to have been absorbed in urban-ized areas. Well aware of the likelihood of increased urban-inducedclimatic change, atmospheric scientists, in an era of heightened eco-logical awareness and sharpened social concern, have addressedthemselves to the task of reevaluation of their research priorities andgoals. A recent report of the National Academy of Sciences Com-mittee on Atmospheric Sciences, for example, listed, among fourmajor research objectives of the 1970’s, "[the establishment of]mechanisms for rationally examining deliberate and inadvertentmeans of modifying weather and climate."1During recent years of steady but unspectacular progress in the

understanding of inadvertent weather changes, no single study hasaroused as much interest, or controversy, over urban weather modifi-cation as the La Porte Weather Anomaly. Central to the theme of theLa Porte Anomaly has been the capacity of large urban-industrialareas to significantly alter precipitation processes and patterns. Thecontroversies have centered over the difficulties atmospheric scien-tists must face in identifying and evaluating such effects. Identifica-tion is hampered by the background "noise" created by many natu-rally occurring variations in the spatial and temporal behavior ofprecipitation, and evaluation is made difficult by inconsistencies indata collecting, or, in many cases, simply by a lack of valid, pertinentdata which can be retrieved for analysis.

THE ANOMALYDevelopments leading to widespread recognition of the anomaly

began when Stanley A. Changnon Jr.j now Head of the AtmosphericSciences Section of the Illinois State Water Survey, investigated theprecipitation record of La Porte, Indiana, a National Weather Ser-vice Cooperative station. The record had indicated a 30% to 40%

’ National Academy of Sciences Committee on Atmospheric Sciences, The Atmospheric Sciences and Man’sNeeds’ Priorities for the Future,^AS-’NRC, Washington, D. C., 1971, p. 78.

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The La Porte Weather Anomaly 209

increase in annual precipitation since 1925,2 and a graph of annualrainfall appeared in phase with the production curve of the Chicagoiron and steel industrial complex 30 miles to the west. Suggested wasa causal connection. By careful and unbiased study of the precipita-tion record, Changnon attempted to determine whether the observedincrease was real, attributable to urban-industrial effects (inadver-tent weather modification) or whether it was a fictional result ofsystemized observer bias or gage site changes.

Publishing the results of his analysis in the Bulletin of the AmericanMeteorological Society in 1968,3 Changnon found that most of theobserved increase had occurred during the warm season (and hencewas likely related to enhanced convectional activity), that it did notrain more often at La Porte than at surrounding cities, (but simplymore heavily), and that La Porte exhibited significantly morethunderstorm days and hail days than adjacent stations. During theperiod 1951 to 1965, when the anomaly was most pronounced,La Porte averaged 31% more precipitation, 38% more thunder-storms, and 246% more hail days than other area stations.

Considering the evidence carefully, Changnon concluded that thefactors indicating a factual increase greatly outweighed those pointingto a fictional increase. Consequently, he surmised that the increasewas real, attributable to the inadvertent modification by the upwindChicago urban-industrial area. Industrial complexes may, in theory,affect precipitation in several ways�by providing condensation andice nuclei, by the addition of heat, and by the addition of water vapor.Changnon did not attempt to evaluate the role of each in contributingto the La Porte anomaly. He felt, however, that the evidence sug-gested that the addition of heat might be a primary cause of theincrease in La Forte’s convective activity and warm season rainfall.Changnon concluded that this case showed valid proof that man

can initiate sizable increases in convective precipitation over andnear large urban-industrial areas. Although considerable previousevidence had existed through both European and U. S. studies thaturban areas could modify precipitation,4 it was the La Porte revela-tions which really caught the public eye, with the results of Chang-non’s study subsequently being reported in Saturday Review, Scien-tific American, Industrial Research, and Newsweek News Focus ^ In

2 Glenn E. Stout, Some Observations of Cloud Initiation in Industrial Areas, Technical Report A62-5, RobertA. Taft Sanitary Engineering Center, Public Health Service, Cincinnati, Ohio, 1962.

a Stanley A. Changnon, Jr. "The La Porte Weather Anomaly�Fact or Fiction?" Bulletin, American Meteoro-logical Society, 1968, 49, 4-11.

4 Stanley A. Changnon, Jr. "Recent Studies of Urban Effects on Precipitation in the U. S." Bulletin, AmericanMeteorological Society, 1969, 50, 411-421.

6]. Lear, "The Home-brewed Thunderstorms of La Porte, Indiana" Saturday Review (April 6, 1968) 53-55."Factory-made Rain" Scieniifie American, 1968,218(4), 49-50."Steel Mills: New Rain Producers" Industrial Research, 1968,10, 7."Steel Mills: New Rain Producers" Industrial Research, (May 1968) II."Heavy Industry in Chicago means more Rain in La Porte" Newsweek, Editors, Neu’s Focus (April 19,

1968)2.

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addition, the increases noted at La Porte bordered on the spectacular,while other precipitation changes previously identified were of muchsmaller magnitude.

THE CONTROVERSIES

Challenge from the scientific world came quickly. Ogden6 investi-gated the records of a number of rainfall stations in the vicinity ofthe Port Kembia, Australia, steel plant and concluded that the steelworks exerted little influence on the annual rainfall totals. He alsoasserted, through the employment of double mass curves, (a statisti-cal technique for revealing the time of change in the station^ climaticrecord), that the rainfall variations at La Porte up to 1940 werecaused by a change in gage site in 1927. Changes observed there afterthat time were unchallenged by Ogden. On the basis of his study,Ogden asserted that "there remained no strong positive evidence thatindustrial activity anywhere has measurably influenced total rain-fall/37

Writing in the Bulletin of the American Meteorological Society,B. G. Hoizman and H. C. S. Thorn8 refuted the existence of a LaPorte anomaly, attributing the apparent rainfall increase to observererror, and concluding that the precipitation record at La Porte was"statistically invalid and physically unacceptable."9Changnon replied convincingly to both the Ogden and Hoizman

and Thorn arguments. He refuted Ogden’s conclusion regarding thelack of evidence that rainfall has been measurably affected by in-dustrial urban activity.10 He questioned Ogden^s use and interpreta-tion of double mass curves, and cited Ogden^s lack of considerationof other anomalous La Porte precipitation conditions (warm seasonrainfall, thunderstorms, and hail) which could not be related to achange in gage exposure. Changnon also concluded that an unsup-ported effect of Port Kembia on the precipitation pattern in its en-virons could not be taken as indicative of lack of a relationship be-tween the Chicago urban-industrial area and La Porte, given theoverwhelmingly larger industrial buildup in Chicago as compared toPort Kernbla.

In his reply to Hoizman and Thorn, Changnon presented addi-tional new evidence including correlations between srnoke-haze days

«T. L. Ogden, "The Effect of Rainfall on a Large Steelworks," Journal a/Applied Meteorology, 1969, 8, 585-591.

’ Loc. cit^ 590.» E.G. Hoizman and H. C.S. Thorn, "The La Porte Precipitation Anomaly" Bulletin, American Meteorologi-

cal Society, 1970, 51, 335-337.9 Loc. cif., 337.10 Stanley A. Changnon, Jr. "Comments on the Effect on Rainfall of a Large Steelworks" Journal of Applied

Meteorology, 1971, 10, 165-168.

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at Chicago and rainfall at La Porte, hail-loss insurance data whichsubstantiated the large observed hail increase, and rain-day fre-quencies per week day, which failed to support fictional explanationsof the anomaly.11 He also cited shortcomings in the HoIzman-Thomarguments concerning (1) how observer error of the required magni-tude could have been perpetrated, (2) their failure (like Ogden) toinvestigate other precipitation data, and (3) inconsistencies between1964-1968 data sources listed by Hoizman and Thorn and thoseshown to have actually existed at La Porte. Changnon concluded thatthe HoIzman-Thom results provided little new information, andrefuted their implication that the La Porte Anomaly was fictional.Hoizman subsequently repeated his allegation of a spurious precipi-

tation record in Science, stating that the "La Porte rainfall record isa celebrated but specious example of man^s inadvertent modificationof climate."12 Replying to Hoizman once again,13 Changnon madereference to his detailed reply to Hoizman’s arguments which hadpreviously appeared in the Bulletin of file American MeteorologicalSociety, and cited a more recent study by Hidore14 which analyzedrunoff from the Kankakee River (the master stream of the drainagebasin within which La Porte is located). Hidore’s results supportedthe existence of the anomaly by indicating a statistical relation be-tween the increase in runoff of the Kankakee River and the increasedprecipitation noted by Changnon for La Porte. Thus Hidore^s study,for the first time, rather than utilizing the station precipitation data,the validity of which had become controversial, centered on otherrelated environmental variables. The wisdom of alternative ap-proaches to the problem was well expressed by Hidore, writing inScience in reply to Hoizman’s latest challenge, who stated "it isthrough continued investigation from a variety of approaches thatthe question of the validity of the La Porte Anomaly will be re-solved."15

Hidore’s study elicited yet another response by Hoizman16 whoasserted that his own study of runoff data in the La Porte Areashowed little or no influence of excessive rainfall at La Porte. Hoiz-man again pointed to observer bias and error as primarily being re-sponsible for "the erroneous precipitation record at La Porte."Hidore, replying to Hoizman’s latest challenge, stated that Hoizman^srunoff data, in fact, supported the anomaly.17n Stanley A, Changnon, Jr. "Reply" Bulletin, American Meteorological Society, 1970, 51, 337-342.

" B. G. IIoIzman "La Porte Precipitation Fallacy" Science, 1971,171, 847.

" Stanley A. Changnon, Jr. "La Porte Anomaly*’ Science (Letters), 1971, 172, 987.

"John J. Hidore "The Effects of Accidental Weather Modification on the Flow of the Kankakee River"Bulletin, American Meteorological Society, 1971, 52, 99-103.

" John J. Hidore "La Porte Anomaly" Science (Letters), 1971,172, 988.

" B. G. Hoizman "More on the La Porte Fallacy" Bulletin, American Meteorological Society, 1971,52, 572-573."JohnJ. Hidore "Reply" Bulletin, American Meteorological Society, 1971, 52, 573-574.

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The debate over the La Porte precipitation record spurred parallelcontroversies over the capacity of industrial sources to modify pre-cipitation. For example, Hobbs, Radke, and Shumway18 publishedthe results of their study of precipitation and streamflow records inthe State of Washington, which revealed increases in the mean an-nual precipitation (over 30% in some cases) in the regions near anddownwind of pulp and paper mills. These industries they describedas large sources of cloud condensation nuclei. The significant inad-vertent changes in precipitation claimed by Hobbs et al, were quicklychallenged. Elliot and Ramsey,19 in correspondence to the Journal ofAtmospheric Sciences, questioned the use of statistics in the study,and the neglect of consideration of several extraneous factors whichthey felt might have altered precipitation patterns. In a reply, Hobbs,Radke, and Shumway refuted their assertions in arguing convincinglyfor the anthropogenic causes of the observed increases.20

THE IMPLICATIONSThe controversy, and more importantly, the interest aroused over

the La Porte data continues. The implications of the La Porte recordextend far beyond the scope of a single station record to indict othermajor urban-industrial areas as precipitation modifiers. The stimulusthus provided by the anomaly in terms of increased awareness of thepotential for inadvertent climatic change posed by a rapidly growingurban population and mushrooming industrial output has beenbrought home to the public as never before. Several research propos-als including a two year grant to the Illinois State Water Survey fora study of precipitation patterns around eight major U. S. cities, anda joint five year field project (Argonne National Laboratory, Univer-sity of Chicago, Illinois State Water Survey, University of Wyoming)to study precipitation conditions in the St. Louis area, beginning in1971, have already been funded. Preliminary results of the IllinoisState Water Survey study have shown evidence of warm season pre-cipitation increases at St. Louis, both cold and warm season increasesat Chicago, and increases in both summer and winter precipitationacross the urban area of Washington, D. C.21The controversies associated with the anomaly have extended the

caution light to researchers attempting to evaluate inadvertent18 P. V. Hobbs, L. F. Radke, and S. E. Shumway "Cloud Condensation Nuclei from Industrial Sources and

Their Apparent Influences on Precipitation in Washington State" Journal of Atmospheric Sciences, 1970, 27,81-89.

19 Wm. P. Elliot and Fred L. Ramsey "Comments on Cloud Condensation Nuclei from Industrial Sources andTheir Apparent Influence on Precipitation in Washington State" Journal of Atmospheric Sciences, 1970, 27,1215-1216.^P. V. Hobbs, L. F. Radke, and S. E. Shumway "Reply" Journal of Atmospheric Sciences, 1970, 27, 1216.21 Floyd A. Huff, Stanley A. Changnon, Ir., and Timothy A. Lewis, "Climatological Assessment of Urban

Effects on Precipitation" Preprints of Papers Presented at Conference on Air Pollution Meteorology, Raleigh,N. C., April 5-9, 1971, 98-103.

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climatic change. Changnon, in analyzing the response to the anomaly,listed four major lessons learned from the anomaly which are appli-cable to the evaluation of inadvertent precipitation modification.22These included: (1) all existing historical weather data at the anomalylocale must be very thoroughly analyzed, in both time and space, anda theoretically sound explanation for the anomaly must be offered;(2) all corroborating geophysical data must be sought and examined;(3) studies of other locales, either similar or dissimilar in climate,where urban industrial complexes exist, are needed, (4) field studiesinvolving physical measurements of urban-industrial effects in theatmosphere interacting with clouds and precipitation must be con-ducted to explain and establish the cause(s).

Continued research attempts to resolve the controversy over theLa Porte data. An abrupt floristic transition near the western marginof the anomaly area has been noted, and a preliminary tree-ringanalysis of red oak near La Porte has given some support to the oc-currence of the precipitation increase.23 Other meteorological featuresin the area, such as lake breeze convergence zones, have also beenrecognized and may play a role in creating anomalous precipitationoccurrences.Although the question of whether the anomaly is real or not may

never be completely answered, much evidence has been presentedwhich suggests that the anomaly is indeed fact, and not fiction. Inany event, the La Porte weather record has focused the attention ofboth scientists and laymen on the delicate balance which exists in theatmosphere, and on man’s innate capacity to alter it.

^Stanley A. Changnon, Jr. "Lessons from the La Porte Anomaly" unpublished paper presented at Inter-national Conference on Weather Modification, Canberra, Australia, September 6-11,1971. Abstract m Bulletin^American Meteorological Society, 1971, 52, 632.

23 Jay R. Harman and Wallace M. EIton "The La Porte, Indiana Precipitation Anomaly" Annals, Associationcj American Geographers^ 1971, 61, 468-480.

The Central Section Meeting of the Illinois Council of Teachers ofMathematics will be held at Illinois State University on April 29, 1972.The chairman of this yearns conference in Normal is Dr. Lotus Hersh-berger, Department of Mathematics, Illinois State University, Normal,Illinois 61761.