CHANGEMENTS DE CLIMAT OF CLIMATE

C H A N G E S OF CLIMATE

Proceedings of the Rome Symposium

orgunized by Unesco und the World Meteorological Orgunization

LES CHANGEMENTS DE CLIMAT

Actes du colloque de Rome orgànisé par 1’ Unesco

et E’Orgunisution météorologique mondiale

U N E S C O

A R I D Z O N E R E S E A R C H - X X C H A N G E S O F C L I M A T E

P R O C E E D I N G S O F T H E R O M E S Y M P O S I U M O R G A N I Z E D B Y U N E S C O A N D W M O

R E C H E R C H E S S U R L A Z O N E A R I D E - X X L E S C H A N G E M E N T S D E C L I M A T

A C T E S D U C O L L O Q U E D E R O M E

O R G A N I S E P A R L ’ U N E S C O E T L ’ O M M

Titles in this series

/

Dans cette collection : I.

II.

III.

IV.

V.

VI.

VIL VIII.

M.

X.

XI.

XII.

xIn.

m.

xv.

XVI.

Reviews of research on arid zone hydrology

Compte rendu des recherches relatives à l’hydrologie de la zone aride Proceedings of the Ankara Symposium on Arid Zone Hydrology

Actes du colloque d’Ankara sur l’hydrologie de la zone aride

Directory of institutions engaged in arid zone research [en anglais seulement]

Utilization of saline water. Reviews of research

Utilisation des euus salines. Compte rendu des recherches

Plant ecology. Proceedings of the Montpellier Symposium

/

Gcologie végétale.

Actes du colloque de Montpellier

Plant ecoZogy. Reviews of research

I

Zcologie végétale. Compte rendu de recherches W i n d and solar energy. Proceedings of the N e w Delhi Symposium

[

lhergie solaire et éolienne. Actes du colloque de

New

Delhi

/

Energia solar y eólicu.

Actas del coloquio celebrado en Nueva Delhi

H u m a n and animal ecology. Reviews of research

/

l?cologie humaine et animale.

Compte rendu de recherches

Guide book to research data on arid zone development

Guide des travaux de recherche sur la mise en valeur des régions arides Climatology. Reviews of research ,

Climatologie. Compte rendu de recherches

Climatology and microclimatology. Proceedings of the Canberra Symposium Climatologie et microclimatologie. Actes du colloque de Canberra

Arid zone hydrology. Recent developments Hydrologie des régions arides. Progrès récents Medicinal plants of the arid zones

Les plantes médicinales des régions arides

Salinity problems in the arid zones. Proceedings of the Teheran Symposium Les problèmes de la salinité dans les régions arides. Actes du colloque de Téhéran Plant-water relationships in arid and semi-arid conditions. Reviews of research Zchanges hydriques des plantes en milieu aride ou semi-aride. Compte rendu de recherches

Plant-water relationships in arid and semi-arid conditions. Proceedings of the Madrid Symposium

[

Echanges hydriques des plantes en milieu aride ou semi- aride. Actes du colloque de Madrid

/

Intercambios hídricos de las plantas en medios áridos y semiáridos. Actas del coloquio celebrado en Madrid

XVII. A history of land use in arid regions

Histoire de l’utilisation des terres des régions arides

XVIII. The problems of the arid zone. Proceedings of the Paris symposium Les problèmes de la zone aride. Actes du colloque de Paris

XIX. Nomades et nomadisme au Sahara

xx.

Changes of climate. Proceedings of the Rome symposium organized by Unesco and W M O

Les- changements de climat. Actes du colloque de R o m e organisé par 1’Unesco etI?OMM

Biodtmatic‘map of the Mediterranean zone. Explanafory nofes Carte bioclim’atique de la zone méditerranéenne. Notice explicative

. J

XXI.

T h e reviews o%rese&ch are published with a yellow cover

;

the proceedings of the symposia with a grey cover.

Lea comptes rendus de recherches sont publiés sous couverture jaune ; les Actes des colloques, sous couverture grise.

Published in 2963 by the United Nations Educational, Scientific and Cultural Organisation

Place de Fontenoy, Paris-Ye

Printed by Vaillant-Carmanne,

S.

A., Liège (Belgique) Publié en 1963

par l’Organisation des Nations Unies pour l’éducation, la science et la culture, place de Fontenoy, Paris-Y8 Impriml par Vaillant-Carmanne,

S.

A., Liège (Belgique)

@ Unesco 1913 Printed in Bein’um

NS.62/111.25/AB

F O R E W O R D

H E arid zone programme

oj’

Unesco, which was started in 1951 with the creation of an Advisory

T

^{Committee on}

^Arid

Zone Research, became one

oj’

Unesco’s Major Projects in 1957.

With

its object of’

promoting and stimulating research in the various scientijîc disciplines which have a bearing upon problems

oj’

the arid regions, the Major Project has proved an excellent example of integrated approach between many d#jbrent disciplines and a successjùl endeavour in inter- national scientijc co-operation having wide educational and cultural implications.

The

ultimate aim of’ the pro- gramme is not only the increase of’ knowledge but also the improvement of’ the living conditions

oj’

mankind and in particular of’ the people living in desert or semi-desert

regions.

A

co-ordinated scientijic effort has commenced in most of these countries not only with an intensijcation of’

existing research programmes but with the establishment and development

o j

special Desert Research Institutes or

Arid

Zone Research Centres whosejunction it is to provide the basic scientijc injormation needed for any development plans.

The

abundance

oj’

injòrmation available in some branches of‘ scientijîc research has become a problem to research workers, and one of Unesco’s tasks has been to publish in this

Arid

Zone Research collection a series of

Reviews of Researeh which have summarized the state

oj’

Icnowledge in a given discipline of science related to arid zone problems.

With

a view to maintaining adequate liaison between the scientists engaged in arid zone research all over the world and to giving them an opportunity to present and discuss the results of their work on spec@ projects, Unesco has also organized a number ofsymposia. Within this fiame- work, and at the suggestion of the

World

Meteorological

Organization

( WMO),

the Advisory Committee on

Arid

Zone Research recommended at its jjteenth session that a symposium on changes

oj’

climate with special reference to the arid zones be organized in 1961 jointly with

WMO.

The

problem of climatic fluctuations is one of extreme complexity and one which relates to many disciplines.

At

the same time it is ofparticularly great importance in the arid zone, where minor variations may have considerable consequences.

The

purpose of the symposium was to bring together scientists who have contributed to the subject from such jelds as meteorology, oceanography, geomorphology, geography, hydrology, botany, geology and even archaeo- logy, so as to obtain a coherent and comprehensive picture ojpresent knowledge, theories and implications

oj’

climatic change.

At

the invitation of’ the Italian Government, the sympo- sium took place in Rome jiom 2 to 7 October 1961.

The

opening ceremony was held in the main hall oj’the Italian National Research Council under the chairmanship of

Projèssor G.

Polvani, president of’ the Council, and speeches were also delivered by M a d a m e Maria Badaloni, [Jnder- Secretary, Ministry of’ Education, Profèssor

A.

Fantoli, representing the Ministry of Foreign Affairs, and General

F.

Giansanti, head o j the Meteorological Service.

Dr.

Luna 5. Leopold, chief’ hydraulic engineer of the

United

States Geological Survey and member of 1Jnesco’s Advisory Committee

fòr Arid

Zone Research, gave an opening address on the importance of’ the problem

oj’

changes of climate, particularly in the arid zones, and proposed that an international programme of‘ observation of’ drainage basins should be organized within the next jèw years.

Some 115 scientists jiom 36 countries took part in the symposium, and the working sessions were held in the conjèrence room oj’the

Food

and Agriculture Organization.

Forty-jîve papers describing original research were presented and discussed during the nine working sessions, and the present volume contains the text of these papers together with a

briej’

summary of’ the discussions to which they gave rise.

As

in previous proceedings, the papers have been reproduced in their original language (English or French).

They

are followed by a summary in the other language.

The

papers have been grouped into four sections :

I.

Changes during the period of’ meteorological records

; II.

Changes during the late geological and early historical

records

;

III.

Theories o j changes

oj'

climate

; I V:

Significance

04'

changes of climate

;

Vi

Conclusions of the symposium.

The

final session consisted of' the presentation and discussion of' a paper by

Dr. C. C.

Wall6n (Sweden) on the conclu- sions to be drawn from all the papers presented.

In accordance with proposals made by the Commission Jòr Climatology the

W M O

secretariat prepared two docu- ments

jòr

the symposium.

The

first-the Bibliography on Climatic Fluctuations-Loas compiled Jrom injòrmation received $-om 28 countries about published and unpub- lished meteorological studies on climatic fluctuations carried out in their countries during the past 10 years.

The

second document is a list of climatological stations

Jòr which observational series extend over 80 years or more.

Information was received from 49 countries

;

17 oj* these have no such stations

;

in the 32 countries, however, there are no less than 791 stutions with records

jòr

80 years or more.

These

two documents have been reproduced by the

W M O

secretariat and distributed to the participants in the symposium.

The

assistance given by the Italian authorities, in particulur by the Meteorological Service, in the organi- zation of' the symposium greatly contributed to its success.

Special credit is due in this connexion to Colonel Luccardi, secretary of' the Italian organizing committee, and to all his stafl.

A V A N T - P R O P O S

E programme de l’Unesco relatif‘ aux terres arides, dont la mise en œuvre remonte ù la création en 1951

L

^d’un Comité consultatif de recherches sur la zone aride, est devenu en 1957 l’un des projets majeurs de l’Unesco.

Ce

projet, qui vise à promouvoir et ù stimuler la recherche dans les diverses disciplines scientijques dont dépend la solution des problbmes des régions arides, constitue un excellent exemple d‘un efort concerté de la part de nombreuses disciplines différentes et représente l’heureuse issue d’une tentative de collaboration scientffique internationale dont les effets, dans le domaine de l’éduca- tion et de la culture, seront considérables. L’entreprise a pour ultime objet, non seulement de servir la science, mais encore d’améliorer les conditions de vie de l’homme et en particulier des populations qui vivent dans les régions désertiques ou semi-désertiques. On a commencé à se livrer

ti des travaux scientijîques concertés dans la plupart de ces pays; non seulement les programmes de recherches se poursuivent avec une activité accrue, mais encore on voit se créer ou se développer des instituts de recherches sur les déserts ou des centres de recherches sur la zone aride, dont le rôle est de fournir les données scientijques sans les- quelles

il

serait impossible d’établir des plans de mise en valeur.

L’abondance des injòrmations dont on dispose dans certaines branches de la recherche scient$que crée pour les chercheurs un véritable problème

;

c’est pourquoi l’Unesco s’est chargée de publier, dans cette collection (Recherches sur la zone aride) une série de comptes rendus de recherches dont chacune résume l’état cles connaissances actuelles dans un domaine scientijque en rapport avec les problèmes de la zone aride.

En

vue de maintenir le contact entre les hommes de science qui, dans le monde entier, se consacrent ù des recherches sur la zone aride, et ajn de leur donner l’occasion de présenter et

de

discuter les résultats de leurs travaux sur des sujets particuliers, l’Unesco a en outre organisé u n certain nombre de colloques.

C’est

dans cette intention que, sur la proposition de l’organisation météorologique mon- diale

(OMM),

le Comité consultatif de recherches sur la

zone aride a recommandé lors de sa 15e session qu’un colloque sur les changements de climat, notamment dans la zone aride, soit organisé en 1961 conjointement avec

I‘OMM.

Les

variations climatiques sont une question d’une complexité extrême qui touche ù un grand nombre de disci- plines et qui, en même temps, présente une importance toute particuliere dans les régions arides, où des change- ments minimes peuvent avoir des conséquences considé- rables.

L’objet

de ce colloque était de réunir des hommes de science dont les travaux ont contribué à la connaissance de cette question dans des domaines tels que la météorologie, l’océanographie, la géomorphologie, la géographie, l’hy- drologie, la botanique, la géologie et même l’archéologie, de façon ùpouvoir obtenir un tableau coordonné et complet des connaissances et des théories actuelles sur les change- ments de climat et leurs effets.

Sur l’invitation

du

gouvernement italien, ce colloque a eu lieu ù Rome du 2 au 7 octobre 1961. L a séance d’ouver- ture s’est tenue dans la grande salle du Conseil national de recherche italien, sous la présidence du professeur

G.

Polvani, président de cet organisme

;

des discours ont été prononcés par M m e Maria Badaloni, sous-secrétaire au Ministère de l’éducation, par le projesseur

A.

Fantoli, représentant le Ministbre des affaires étrangères, et par le général

F.

Giansanti, chej’ du Service météorologique.

Le D*

Luna

B.

Leopold, ingénieur hydraulicien en chej’

du Geological Survey des &tats- Unis d’Amérique et membre du Comité consultatif de recherches sur la zone aride, de l’Unesco, a jait un exposé général sur l’impor- tance du pro blème des changements de climat, en particulier dans la zone aride

;

il a proposé qu’un programme inter- national d’observation de bassins versants soit 6tabli au

COUTS des prochaines années.

!%Au nombre de 115, des hommes

de

science venus de 36 pays se sont rencontrés pour participer ù ce colloque;

les séances de travail se sont tenues dans une des salles de conférence de l’organisation pour l’alimentation et l’agriculture.

A u cours de 9 séances de travail, 45 communications

relatives ù des recherches originales ont été présentées et discutées

;

le présent volume contient le texte de ces commu- nications, ainsi qu’un bref’ résumé des discussions aux- quelles elles ont donné lieu. Conjarm6ment aux précédents, les communications sont reproduites dans la langue ori- ginale (anglais et français) avec un résumé dans l’autre langue.

Elles

ont été groupées en quatre sections

: I.

Changements survenus au cours de la période

couverte par les observations météorologiques.

II.

Changements survenus à laJin des temps géologiques et au début des temps historiques.

III.

Théories des changements

de

climat.

IV.

Portée des changements de climat.

V.

Conclusions du colloque. Derniere séance consacrée à la discussion d’un rapport de synthèse sur les résultats du colloque présenté par le

D* C. C.

Wallén (Suede).

Conformément à une proposition de la Commission de climatologie, le secrétariat de

l’OMM

avait préparé deux documents en vue de ce colloque.

Le

premier

- ^Biblio-

graphy on climatic fluctuations

-

^{avait été} établi sur la base

de

renseignements fournis par 28 pays au sujet

des

études météorologiques, publiées ou inédites, efectuées sur leur territoire au COUTS des dix dernières années ^SUT 1esJluctuations climatiques.

Le

deuxième document est une liste des stations climatologiques dont les séries d’observa- tions s’étendent sur quatre-vingts années et plus.

Cette

publication réunit les renseignements envoyés par 49 pays

;

dans 17 d’entre eux,

il

n’existe pas de station de ce genre

;

mais dans les 32 autres, on n’en compte pas moins de 791 dont les relevés couvrent quatre-vingts années ou davantage.

Ces

deux documents ont Été reproduits par le secrétariat

de l’OMM

et distribués aux participants du colloque.

L’organisation du colloque a été grandement facilitée par les autorités italiennes

-

notamment par le Service météorologique

-

qui ont ainsi largement contribué au succès de la réunion. Des remerciements tout particuliers sont dus au colonel Luccardi, secrétaire du comité italien d’organisation, ainsi p ’ ù tous ses collaborateurs.

’

I.

C O N T E N T S

T A B L E D E S M A T I È R E S

Changes during the period of meteorological records

J

Changements survenus au cours de la p6riode couverte par les observations météorologiques

A

review of studies on climatic fluctuations during

the

period of the meteorological record,

by

Aperçu des études relatives aux variations climatiques intéressant la période pour laquelle on clispose d’observations météorologiques, par

R. G.

Veryard

. . . . . . . . . . .

Sur la détermination de la stabilité des séries climatologiques, par

R.

Sneyers

. . . . . .

Determination of

the

stability of chronological series [summary]

. . . . . . . . . A

quantitative definition of

the

meaning of constancy and steadiness of climate,

by

Ezio Rosini

. . Une

définition quantitative de constance et de stabilité d’un climat [résumé]

. . . . . .

Climatic changes

in

India,

by K. N.

R a o and

P.

Jagannathan

. . . . . . . .

fivolution

du

climat de l’Inde [résumé]

. . . . . . . . . . . . . .

Climatic fiuctuations in the

Midclle

East during the period of instrumental record,

by N.

Rosenan

.

Variations climatiques observées au Moyen-Orient depuis la mise en service des appareils enregistreurs [résumé]

. . . . . . . . . . . . . . . . . . . .

Contributions au problème des changements de climat. survenus au cours

de

la période couverte par les observations météorologiques faites dans le nord de l’Afrique, par

J.

Duhief .

. . . . .

Contribution to the problem of climatic changes during

the

period covered

by

the meteorological observations made

in

northern Africa [summary]

. . . . . . . . . . . R. G.

Veryard

. . . . . . . . . . . . . . . . .

.

.

Temperature and rainfall trends

in

South Africa during the period of meteorological records,

by W. L.

Hofmeyr and

B. R.

Schulze

. . . . . . . . . . . . . .

Les tendances

de

la température et de la pluviosité en Afrique

du Sud

pendant la période pour laquelle on possède des données météorologiques [résumé]

. . . . . . . . . . .

Secular trends in the soil temperatures at Colaba, Bombay,

by L. A.

R a m d a s and

N.

Rajagopalan

.

Tendances séculaires des températures

du

sol

à

Colaba (Bombay) [résumé]

. . . . . .

Climatic fluctuations

in

the arid zone of the Ukraine,

by I. E.

Buchinsky

. . . . . . .

Les fluctuations climatiques dans la région aride de l’Ukraine [résumé]

. . . . . . .

Sea-surface temperatures of

the

North Atlantic Ocean during the decade

1951-60,

their anomalies and development

in

relation to the atmospheric circulation,

by M.

Rodewald

. .

.

. .

L a température superficielle

de

l’océan Atlantique au cours de la décennie

1951-1960,

ses anomalies et son évolution

ea

relatioiz avec

I,&

circulation a,tmosphérique [résumé]

. . . . . . . .

3

17 37 43 45 48 49 64%

67

73

75

78

81

84

87

90

91

95

97

105

Climatic fluctuation over the oceans and

in

the tropical Atlantic,

by P. R.

Brown

. . . . .

Les fluctuations climatiques sur les océans et dans la partie tropicale de l’Atlantique [résumé]

. . On

the nature of certain climatic epochs which diffcred from the modern

(1900-39)

normal,

by

H. H.

L a m b

. . . . . . . . . . . . . . . . . . .

D e la nature de certaines époques climatiques qui se sont écartées de la c normale x moderne

(1900-1939)

[résumé]

. .

,

. . . . . . . . . . . . . .

, ,

. On

the climatic variation,

by L.

Lysgaard

. . . . . . . . . . . . .

Variations climatiques [résumé]

. . . . . . . . . . . . . . . . On

the world-wide pattern of secular temperature change,

by J.

Murray Mitchell, Jr.

L a répartition mondiale des variations séculaires de température [résumé]

. .

,

. . . . . .

Climatic fluctuations studied

by

using annual flows and effective annual precipitations,

by V. M.

Yevdjevich

. . . . . . . . . . . . . . . . . .

Etude des fluctuations climatiques au moyen des

débits

annuels et des précipitations annuelles effec- tives [résumé]

. . . . . .

,

. . . . . . . . . .

109 122

125 147 151 158 161 180

183 200

II.

Changes during the late geological and early historical records Changements survenus à la fin des temps géologiques et au &but des temps historiques

Changes of climate

during

the late geological record,

by K. W.

Eutztr

. . . . . . . 203

Les changements

de

climat pendant les ères géologiques les plus récentes, par

K. W.

Butzer

. . . 205

Paleosoils as indicators of paleoclimates,

by W. L.

Kubiena

.

,

. . . . . . . . 207

Les paléosols en tant qu’indicateurs

de

paléoclimats [résumé]

. . . . . . . . . 208

The last “pluvial” phase of the Eurafrican sub-tropics,

by K. W.

Butzer

. . . . . . . 211

L a dernière phase K pluviale n de la zone subtropicale eurafricaine [résumé]

. . . . . . 218

Simultaneity of glacial and pluvial episodes from

C-14

chronology of the Wisconsin glaciation,

by

L a simultanéité des épisodes glaciaires et pluviaux dans la glaciation

du

Wisconsin d’après la datation

RLRubin

,

. . . . . . . . . . . . . . . . . . . 223

au moyen

du

carbone-14 [résumé]

.

,

. . . . . . . . 227

Mean sea level related to solar radiation

during

the last

20,000

years,

by R. W.

Fairbridge

. . . 229

L e niveau moyen des mers et le rayonnement solaire au cours des

20 O00

dernières années [résumé]

. 240

D e l’application

de

techniques pdynologiques à un territoire désertique. Paléoclimatologie

du

quater- Palynology of

the

Recent Quaternary in the arid and desert zone of northern Africa and its paleoclimatic naire récent au Sahara, par

P.

Quézel

. . . . . . . . . . . . . . 243

effects [summary]

. . . . . . . . . . . . . . . . . . 248

,/ S u m m a r y of prehistoric investigations

in

Kurdistan

in

relation to climatic change,

by R. J.

Braidwood Exposé sommaire des résultats de recherches préhistoriques faites au Kurdistan relativement aux modi-

251

fications

du

climat [résumé]

. . . . . . . . . .

,

. . . . . 253

Recent advances in dendrochronology

in

America with reference to the significance of climatic change,

by H. C.

Fritts

. . . . . . . . . . . . . . . . . 255

Progrès récents en matière de dendroclimatologie en

Amérique

[résumé]

. . . . . . . 261

S o m e climatic indicators in the period A.D.

1200-1400

in N e w Mexico,

by L. B.

Leopold,

E. B.

Leopold and

F.

Wendorf

. . . . . . . . . . . . . . . . . . . 265

L a sécheresse

de 1200 à 1400

après

J.4

dans le sud-ouest des ‘&tats-Unis [résumé]

. . . . 269

S o m e remarks on the last climate fluctuation in the Arctic regions and in central Europe,

by A.

Kosiba Remarques sur la dernière fluctuation climatique enregistrée dans les régions arctiques et en Europe centrale [résumé]

. . . . . . . . . . . . . . . . . .

III.

Theories of changes

oj’

climate

Théories

des changements de climat

Theories of recent changes of climate

by R. C.

Sutcliffe ,

. . . . . . . . .

Théories relatives aux changements de climat récents, par

R. C.

Sutcliffe

. . . . . . .

Fluctuations of general circulation of the atmosphere and climate in the twentieth century,

by B. L.

Dzerdzeevskii

. . . .

.

. . . . . . . . . . . . .

Les fluctuations de la circulation générale de l’atmosphère et

du

climat au X X ~ siècle [résumé]

.

Climatic change as a n ocean-atmosphere problem,

by J.

Bjerknes

. . . . . . . .

Les fluctuations climatiques, conséquences de l’action réciproque de l’océan et de l’atmosphère [résumé]

T h e influence of the variability of solar and terrestrial radiation o n climatic conditions,

by W. L.

Godson L’influence de la variabilité des rayonnements solaire et terrestre sur les conditions climatiques [résumé]

Notes on the response of the general circulation to changes

in

the solar constant,

by J. S.

Sawyer

.

Notes sur l’effet des changements de la constante solaire sur la circulation générale [résumé]

. .

Theories of climatic change from the viewpoint

of

the global energy budget,

by H. Flohn .

Théories des changements de climat du point de vue

du

bilan énergétique global [résumé]

.

Surface-atmosphere interactions as fundamental causes of drought and other climatic fluctuations,

by J.

Namias

. . . . . . . . . . . . . . . . . . . .

L’interaction

de

la surface de la terre et de l’atmosphère en tant que cause fondamentale de lasécheresse et des autres fluctuations climatiques [résumé]

. . .

.

. . . . . . A

numerical study of the effect of vertical stability on monsoonal and zonal circulations,

by E. B.

Kraus

and

E. N.

Lorenz

. . . . . . .

.

. . . . . . . . . .

fitude numérique de l’influence de la stabilité verticale sur les circulations de mousson et zonales [résumé]

. . . . . . . . . . . . .

Essai d’explication héliogéophysique des changements paléoclimatiques, par

A.

Obuljen

. . .

A

tentative heliogeophysical explanation of palaeoclimatic changes [summary]

. . . . . .

. . .

.

IV. The

signijicance of’ changes oj’climate

/

Portée des changements de climat

T h e significance of climatic change for natural vegetation and agriculture,

by R. O.

W h y t e

. .

Conséquence des modifications

du

climat pour la végétation spontanée et l’agriculture, par

R. O.

W h y t e T h e quaternary climate as a morphological agent

in

Iraq,

by C.

Voûte and

E. J.

W e d m a n

.

L e climat quaternaire en tant qu’agent morphologique en

Irak

[résumé]

. . . . . . .

Nature and implications

of

quaternary changes in Iran,

by H.

Bobek

. . . . . . .

Nature et conséquences das changements de climat

à

l’époque quaternaire en Iran [résumé]

. .

Oscillations et modiíications de caractère de la zone aride en Afrique et en Amérique latine lors des périodes glaciaires des hautes latitudes, par

J.

Tricart

. . . . . . . . . .

Oscillations and characteristic modifications of the arid zone

in

Africa and Latin America

during

the periods of

high

latitude glaciation [summary]

. . . . . . . . . . . .

Simple measurements of morphological changes in river channels and

hill

slopes,

by J. P.

Miller and

L. B.

Leopold

. . . . . . . . . . .

,

. . . . . . .

Expériences sur

le

terrain

en

vue de l’étude géomorphique des effets des variations climatiques [résumé]

. . .

271 273

277 281 285 292 297 319 323

330

333 336 339 343 345 358 361 372 373 377

381

387

395

401

403

4110

415

418

421

426

Relations des fluctuations climatiques avec l’hydrologie. l’agriculture et l’activité humaine en

Afrique du

Nord. par

J .

Tixeront

. . . . . . . . . . . . . . . . .

Effects of climatic fluctuations on Lhe hydrology and economy of arid regions [summary]

L’influence des changements de climat sur la colonisation des terres arides [résumé]

. . .

Effects of climatic change

in

an arid environment on land-use patterns.

by D . H . K .

Amiran

. . . . . .

.

A

review of evidence concerning changes of climate

in

India during the protohistorical and historical periods.

by S . K . Seth . . . . . . . . . . . . . . . . . Les

changements de climat dans l’Inde. analyse des données [résumé]

The significance of climate variations in Britain.

by L . P . Smith . . . . . . . . . . . . . . . .

Les effets des variations

du

climat en Grande-Bretagne [résumé]

. . . . . . . . V .

Conclusions of’ the symposium

I

Conclusions du colloque

Aims and methods

in

studies of climatic fluctuations.

by C . C .

Wallén

Objectifs et méthodes des études sur les fluctuations climatiques. par

C . C .

Wallén

. . . . .

. . . . . . .

List of participants

/

Liste des participants

. . . . . . . . . . . . . .

429 437 439 443

445 454 457 465

469 476

487

S E C T I O N I

C H A N G E S D U R I N G T H E P E R I O D O F M E T E O R O L O G I C A L R E C O R D S

C H A N G E M E N T S S U R V E N U S

AU C O U R S D E L A P É R I O D E C O U V E R T E

P A R LES OBSERVATIONS M É T É O R O L O G I Q U E S

Chairman

/

Président :

DR. R. G. VERYARD

A R E V I E W

O F STUDIES O N CLIMATIC F L U C T U A T I O N S D U R I N G T H E P E R I O D

O F T H E M E T E O R O L O G I C A L R E C O R D

bY

R. G. V E R Y A R D

Meteorological Ofice, Air Minishry, London

FOREWORD

During the early stages of the planning for this sympo- sium it was proposed that the first session should be devoted mainly to a review paper covering the whole

field

of the symposium and that some provocative ideas should

be

thrown eut as a basis for the subsequent discussions. T h e latter requirement presents no difficulty as there is ample scope for argument regarding the methods, criteria and theories for determining and explaining climatic fluctuations. But to summarize facts -and fancies-in respect of all the aspects of climatic change to be discussed at the symposium would call for an

unduly

long disquisition on

highly

heterogeneous material

in

m a n y hundreds of papers. In any case, as there is to be a review paper for each session, it is hoped that it

will

be sufficient

if

this review paper (for Session

I)

relates almost entirely to the period of the meteorolo- gical record. It m a y

be

mentioned that, in order to ensure the availability of comprehensive information for study before the symposium, the World Meteorological Orga- nization

(WMO)

called

upon

each member country to supply particulars of all climatological studies carried out

in

the country since

1950,

plus particulars of the more important studies prior to

1950

(now issued

by WMO in

a publication entitled Bibliography

on

Climatic Fluctuations). Although all members

did

not respond to the appeal, the replies received showed that a stag- gering number of papers had been written amounting to over

300

in North America and a comparable number

in

Europe, the total exceeding

700. A

large number of the studies,

in

m a n y c2ifferent languages, related to the period of the meteorological record and it has not been possible,

in

the time available, to digest or even to obtain access to

all

the papers.

So

the author of this review m a y perhaps

be

forgiven

if

certain findings are overlooked. For the same reason, it is hoped that authors

will

not feel aggrieved

if

special mention of their work

is

not included

in

this paper.

By

far the greater number of papers have been of a statistical nature and,

in

spite

of the rapid development

in

recent years of a dynamical approach to the study of the general circulation, only in a comparatively

few

climatological s tudies has this approach been used. Further reference to this poiiit

w i l l

be made later.

METHODS

T h e methods of determining the existence and magni- tude of climatic fluctuations vary from the old-fashioned simple analysis for various elements of departures from

“normal” (the normal being an average value based o n some selected period, generally

30

years) or the use of

“running means”-to the modern and more advanced

“power-spectrum analysis” of a time series using elec- tronic computers. In regard to use of a “normal” period the question arises whether any period can really be regarded as “normal”. In any case,

a

comparison of means of different periods is of little use without a n examination of the nature of the frequency distribution.

Also,

the

use of moving averages has its limitations.

So,

whatever the method, there is always need for precaution and doubtless some of

the

more important statistical pitfalls

will

be mentioned during the discussion at this session.

In

this connexion, it m a y be useful to mention that a special chapter, written

by

experts, on the use of statistical methods

will

be included

in the WMO

Guide to Climatological Practices n o w under publication.

O n e important precaution which has to be taken is to ensure the representativeness and homogeneity of the basic data.

A

comprehensive study of the causes of instrumentally observed secular temperature trends has

been

carried out

by

Mitchell

(1953).

H e draws attention to m a n y factors which are not always realized; for example,

the

effect of urbanization

in

causing an “arti- ficial“ temperature rise at city meteorological stations,

A

c o m m o n practice is the construction

of

time series from mean monthly temperatures based on mean daily

3

Changos of climate

1

Les changements de climat

max. $- min.

temperatures calculated from ,

It

is deba- table, however, whether such values are really adequate for assessing climatic change. For example, Marshall

(1954)

using data for

Kew

Observatory has shown that the m e a n monthly temperature is sometimes unrepresentative and occasionally misleading as a means of comparing one particular month

with

the same month

in

other years.

As

he suggests, the mean m a x i m u m and mean minimum temperatures m a y

be

m u c h better criteria of the temperature characteristics of a month.

Attention is also drawn to a recent paper

by

D e Vries and Birch

(1961)

which indicates that, according to the irrigation rate and distance down-wind from the irri- gated area, irrigation m a y exert an appreciable, even

if

mainly local, influence on the distribution

of

energy and thereby on the climate near the ground.

The

authors found that for the irrigation seasons of

1956-57

and

1957-58 in

the Nanneella district east of Rochester in Victoria (Australia), the differences of temperature at screen level between a “dry-land” station and a station

in

the irrigation area could be as much as

1-2oC.

Maybe, in addition to “urbanization”, irrigation, and pollution there are several other important effects of man’s activities on local,

if

not regional or global cli- mate, which could lead to “fluctuations”

in

a time series of temperature, rainfall, etc. Again, and n o w the writer is

riding

his favourite hobby-horse, are not mean monthly values of temperature, rainfall, etc., of very limited use for the study of climatic fluctuations -because of the short-term variations

(due

to thunder- storms, moving highs and lows, etc.)

within

a month

? It

has been suggested that time averages might be replaced

by

ensemble averages-but h o w does one choose the ensemble

?

In recent years, harmonic analysis appears to have become less popular-but the hunt for “cycles” still goes on. Berlage

(1957)

has listed all the m a n y “cycles”

which have been “discovered”

by

various investigators -yet it seems that not one of these has

been

established beyond doubt. Indeed, experience

with

long-period records suggests that one cannot really expect to break down fluctuations into unique periodicities of different

but

exact wavelengths. Often the time series shows something

like

a “beat” phenomenon-but

with

an unevenly

varying

wave-length. For example, a recent study of tropical stratospheric

winds by

Veryard and Ebdon

(1961)

indicates a waxing and waning fluctuation in the zonal component varying from

23

to

29

months,

the

average period

being 26

months.

Indeed,

there can

be

no doubt that various lag effects, feed-back mecha- nisms, etc., operate over periods of a considerably different time scale. For dealing

with

this problem, power-spectrum analysis m a y provide the answer and a good example is

the

study of the rainfall at Woodstock College

by

Lansberg, Mitchell and Crut- cher

(1959). A

few last words before leaving

the

subject of methods.

It

is surprising h o w m a n y workers in the

field

of climatic fluctuation have ignoikl not only the variance of the element being studied

but

also the possibility that the distribution of the element m a y not

be

a ‘(normal‘’ or “circular” one and m a y ,

in

lact, have two or more modes.

Of

course, it is not so easy to determine statistically significant time changes of variance and extreme values as of means but it

will

doubtless

be

agreed that studies of climatological fluctuations should not

be

based solely on mean or average values but that adequate attention should

be

given to frequencies and extreme values.

FINDINGS

N o one can deny that the climate does change and that

there

are fluctuations varying from the small scale invo1ving.a century or so to the large scale involving millions of years and embracing the great Ice

Ages. In

the former category are the fairly well authenticated changes which have occurred

in

historical times

in

the countries bordering on the North Atlantic. Thus there is good reason to believe that following an “optimum”

period of climate about

2000-4000

B.C.,

when

temper- atures were some degrees higher than today, there have been several variations. For example, according to Brooks

(1954),

there

were

several climatic phases in the last

10

centuries: a mild, relatively

dry

period from before A.D.

1000

to

1250

followed

by

a rainier, stormy period from about A.D.

1250

to

1400,

then a period of colder but less stormy weather from A.D.

1400

to

1600

when sea ice increased but mountain glaciers were still relatively small, and then the “Little Ice Age” from A.D.

1600

to

1850 when

glaciers oscillated about a n advanced position

with

three main maxima, about

1650, 1750

and

1850.

Finally, w e come to the period of the meteorological record.

It

was not until the nineteenth century that the measurement of meteorological

ele-

ments

by

means of instruments really got under w a y and

by

the end of that century,

with

the encouragement of the International Meteorological Organization (the predecessor to

WMO),

instrumental meteorological observations, based on standard procedures and prae- tices, became fairly world-wide. Attempts have been made, e.g.,

by

Manley

(1959)’

to reconstruct, from all the instrumental data available,

the

temperature régime back to the end of the seventeenth century.

But

owing to site changes, breaks due to wars, etc., there are as yet very few really homogeneous long-period records.

Nevertheless, such records as are available, including synoptic charts and non-meteorological evidence such as

the

measurement of glaciers, have m a d e it possible to get some idea of the existence of climatic “trends” o n fluctuations

during

the last

100-200

years-at least for a great part of the Northern Hemisphere,

but

only for a few areas

in the

Southern Hemisphere.

It

so happens that this period of the meteorological record has been a period of retreat of glaciers, of decreasing ice cover

4

Review of studies on climatic fluctuations

and of rising temperatures and it.

is

this most recent climatic fluctuation which has been the subject of innumerable papers.

In the following paragraphs an attempt is m a d e to extract the “meat” from these papers under the headings of “Temperature”, “Precipitation” and “Pressure, pres- sure patterns and

winds”.

T E M P E RAT U R E

Air

temperature

It is n o w generally accepted that the most striking feature of climatic fluctuations during the period oî the meteorological record has been a warming in m a n y parts of the world since about

1850

until a decade or two ago when

in

some places, but not all, there appears to have been a levelling-off or a fall of temperature. Let us look at the evidence.

F r o m a carefully compiled long-period temperature record for Delft, Zwanenburg, Utrecht and D e Bilt, Labrijn

(194*5)

has shown,

by

means of overlapping 30-year means, that up till

1945

there was a general rise in winter m e a n temperature in the Netherlands from about

1790

onwards (apart from a slight relapse at about

1890)

and a slow increase

in

summer m e a n tem- perature from about

1800

until the end of the nineteenth century and thereafter a decrease until about

1920

fol- lowed

by

another rise.

A

decreasing cWerence between summer and winter temperature, especially from

1400

onwards, indicated that the warming was accompanied

by

decreased continentality. For Iceland, Eythorsson

(1949)

found a steady rise of annual temperature of about

1.10 C.

from approximately

1316-25

to

1926-35,

the rise starting earlier

in

the north than in the south of the country. From long-period temperature records t‘or Helsinki and Oulu, Keranen

(1952)

concluded that the climate of Finland had become continuously milder during the seventeenth century

with

a peak warming

in

the

1930s, but

some levelling-off in Lhe

1940s.

For Lapland, Blüthgen

(1952) found

that the m e a n annual temperature for the period

1935-50

showed a rise of

10 C.

over that for the period

1901-30

whilst corresponding means for November and December showed a rise of 30

C.

For Norway, the studies of Hesselberg and Birkeland

(1956)

and Hesselberg and Johannessen

(1958)

show that there was a rapid rise

of

temperature at Norwegian stations

in 1917-22

especially at Spitsbergen, e.g.,

7O C. in

winter, 30

C.

in spring,

20 C. in

summer,

30 C. in

autumn, and

40 C.

for the whole year. T h e rise continued after

1922

but at a slower rate (lo

C.

per year) with a greater increase at Spitsbergen than farther south. T h e peak of the fluctuation was reached in the

1930s,

having been greatest in winter a n d smallest

in

summer.

In 1941-50

there was a reversal of the trend especially with the cold winters of

194042.

There are several other studies on temperature fluc- tuations

in

western Europe but the results are rather

conflicting. For example, Glasspoole

(1955)

using 10-year moving averages of temperature for the British Isles found marked digerences in curves for England and Wales and for Scotland although on the whole the trends were very similar with a n increase of about

0.50 C.

in the annual temperature from

1922-31

to

1929-38.

For England and Wales he found a steady increase of over

lOC.

from

1923-32

to a peak in

19483-52

in spring, a very rapid increase in summer of about

10 C.

from

1922-31

to a peak

in 1932-41

followed

by

a decrease, and a steady increase

in

autumn of nearly 1 O C . from

1918-27

to a peak in

1942-51.

Whilst the rise

in

temperature in autumn started earlier than in spring or summer and continued for a longer period, the curves for These three seasons were similar

;

but the curve for h t e r was more nearly a mirror image of the others. Thus the winter curve shows a general decrease of over lo

C.

from a m a x i m u m

in 1918-27

to a minimum

in 1937-46

which was followed

by

a rapid increase of over

0.50 C.

until

1942-51,

S

teinhauser

(1960)

has demonstrated that during the period

1901-30

the climate of cenlral Europe showed very strong oceanic influence. This is particularly noii- ceable

in

a curve given

by

Steinhauser et al.

(1957)

showing fluctuations in the variance of temperature at Vienna for which a long-period record is available; in the

1870s/80s

and from the

1930s/40s

onward the variance w a s approximately twice as m u c h as that in the period in between. Using this long-period record for Vienna and also long-period records for Berlin, D e

Bat,

Basle and Milan, Steinhauser gives some interesting curves of

5-, lo-,

and 30-year running means of annual temperature. Whereas the curves for Basle and hlilan run almost parallel, these curves and the remaining curves show little correspondence on the whole; for some years they move together and for others they diverge or converge. It is interesting to note that decadal averages for Vienna which showed a rise

in

the

1930s

were thrown back

by

the three cold years

01 1940-42

but subsequently exceeded all previous values.

E. S.

Rubinshtein

(1956) in

a detailed study of climatic changes

in

the

U.S.S.R.

during the

30-40

years

up

to

1950-55

found a warming trend, most noticeable

in

the winter months, which culminated

in

the thirties

;

but whereas there was a decline from then on over a consi- derable area, especially the western U.S.S.R., the warming trend continued at high latitudes of the U.S.S.R., e.g., Januaries

in

the Barents Sea were very w a r m

up

to

1950

and high winter temperatures persisted in the estuaries of the rivers O b , Yenisey and on the Arctic Ocean coast. Rubinshtein also found that the peak warming periods

in

the eastern regions of the Asiatic territory of the

U.S.S.R.

were not always concurrent with those

in

western Siberia and European

1I.S.S.R.

She emphasized, and this is a point m a d e

by

other workers, that not all years

in

the period of consi- derable warming were w a r m but that there was simply a tendency for w a r m years to prevail. Commenting on

5