It is often assumed that the climate of Africa has been more humid even in historic times. The geographer Leo Berg in Petrograd, however, is emphatically opposed to this theory. He points out that the writers of antiquity, Diodoros, Polybios, and Pausanias, have given descriptions of the rivers on the North African coast which nearly agree with conditions today. The location of two ancient cities on the shores of Lake Chott-el-Djerid in Tunis (Lacus Tritonis of old), which lake, it is claimed, reached a level very much higher than now 500 years B.C., plainly demonstrates that the shore-line then ran very close to its present position. Students of ancient Egypt are unable to find evidence of any distinct difference in the climate of that country from the earliest times to our days. It is true that marshes in the Nile delta have changed into splendid meadows—but this is the work of man. The humid period must have ended long before history commenced. A few of the old writers, such as Herodotos, Aristophanes, and Philo, assert that rain never falls in Egypt, but this must be classed as an exaggeration when contrasted with references to rain, snow, and hail in this section made by other ancient authors, for instance Plutarch, Pliny, and Ælianus. At any rate it seems as if precipitation was as rare an occurrence in the land of the Pharaohs as in the land of the Nile of today.
Against the statement by Huntington that the climate of Palestine has become very much more torrid during historic times, stands the assertion by Hilderscheid, who has made a thorough study of these questions, that no reason whatever exists for such a conclusion.
Of greatest interest to us in this connection are perhaps Italy and Greece. Huntington believes that the river Alpheios, which flooded Olympia and covered it with a 4 m. to 5 m. (4 or 5 yards) thick sediment, carried a far greater volume of water formerly than today. This flood, however, was caused by an earthquake accompanied by a fall of rocks whereby the river was dammed. There is no necessity for assuming a greater abundance of the waterflow. According to Strabo, the streams Kefissos and Ilissos, between which Athens is situated, dried out during the summer then as they do now. If we are to believe Pausanias, the brooks which traversed the Argive plain behaved similarly, and so they behave today. From all we can judge, the climate of Greece has not changed perceptibly since the days of Homer.
In regard to Sicily, it is stated that several of its rivers were navigable in the Middle Age, while such is not the case now. But this is explained by the devastation of the forests which formerly equalized the flow of these rivers, and perhaps also by the size of the vessels of that time. Cultivation in these regions has sharply declined since antiquity. As a consequence, the loose soil, which formerly was planted, has been washed away and the dams and retaining walls, built to prevent a too rapid drain of the water, have disappeared. Thus the country has grown increasingly arid. Large cities, as Palmyra, existed in desert regions where lack of water now prevents habitation. But water was brought to the metropolitan cities of old through long magnificent aqueducts, the ruins of which partly remain today. We have all reasons to believe that the marked decrease in cultivation and population, laid to changes in conditions of humidity, depended altogether on man’s interference with nature. On certain rocks in Morocco, carvings have been found portraying in a simple way large mammals such as elephants, rhinoceroses, and giraffes, which do not exist in these regions now because of lack of nourishment. But these rough works of art, resembling those of the bushmen of today, date from prehistoric time, the so-called paleolithic era, when the climate admittedly was more humid in these regions than it is now.
Similar conditions obtain, according to Hedin, in Central Asia and in Persia. The climate there has without doubt been more humid but not in historic times. The march of Alexander toward India took place under as adverse conditions as now are found in these regions (Baluchistan). Their cities, now in ruins, received their water supply through conduits from rivers some of which were then adjacent to the cities, although they later have changed their course as pointed out by Leo Berg.
In Western and Central Europe numerous marshes and morasses have indeed been drained and rendered available for cultivation, but this does not prove that the climate is become more dry. On the contrary all observations, for instance those made by Tycho Brahe on the island Hven, indicate that the difference between summer and winter temperature has decreased during historic time; that is the climate is become less continental, or more humid, than formerly. Furthermore, many circumstances, such as the occurrence of hazel and of water chestnut in far more northerly latitudes and the higher altitude of the timber line in earlier time, prove that the summer in prehistoric ages was warmer than now. Simultaneously it was dryer. A study of the lacustrine pile dwellings in Switzerland shows that the levels of the lakes then were not higher than now but very nearly the same, which demonstrates that the precipitation has not changed perceptibly in Switzerland since these buildings were made; the period in question occurred, we believe, about 7000 years ago.
While great climatic changes have taken place since man’s first appearance on earth, presumably before the end of the ice period, historic time is too short to record any distinct modifications. Local ones may be in evidence such as West Europe’s transition to a less continental climate. A variation of this nature has been found not longer back than since thermometrical observations commenced. Thus the winters in Berlin during the period 1746–1847 were colder and the summers warmer than during 1848–1907. The difference for January amounted to -1.5° C. (-2.7° F.) and for May to +0.6° C. (+1.08° F.). The tabulation below, quoted from Ekholm, shows the mean temperature in Stockholm, Lund, London, and Paris, during winter (December-February), spring (March-May), summer (June-August), and autumn (September-November) and for the following periods:
| Stockholm | Lund | London | Paris | |||||
| 1799– 1848 | 1849– 1898 | 1753– 1798 | 1799– 1898 | 1799– 1848 | 1849– 1898 | 1806– 1848 | 1849- 1898 | |
| Winter | +25.5° F. -3.6° C. | +26.8° F. -2.9° C. | +30.2° F. -1.0° C. | 30.9° F. -0.6° C. | 38.5° F. 3.6° C. | 39.2° F. 4.0° C. | 37.9° F. 3.3° C. | 37.9° F. 3.3° C. |
| Spring | 37.9° F. 3.3° C. | 37.9° F. 3.3° C. | 41.2° F. 5.1° C. | 41.5° F. 5.3° C. | 48.2° F. 9.0° C. | 48° F. 8.9° C. | 50.5° F. 10.3° C. | 50.3° F. 10.2° C. |
| Summer | 60° F. 15.6° C. | 60° F. 15.6° C. | 61° F. 16.1° C. | 60.2° F. 15.7° C. | 61.9° F. 16.6° C. | 62.2° F. 16.8° C. | 64.6° F. 18.1° C. | 64.8° F. 18.2° C. |
| Autumn | 43.9° F. 6.6° C. | 43.5° F. 6.4° C. | 45.9° F. 7.7° C. | 45.9° F. 7.7° C. | 50.7° F. 10.4° C. | 50.5° F. 10.3° C. | 54.2° F. 11.3° C. | 51.8° F. 11.0° C. |
| Year | 41.9° F. 5.5° C. | 42.1° F. 5.6° C. | 44.6° F. 7.0° C. | 44.6° F. 7.0° C. | 9.8° F. 9.9° C. | 50° F. 10.0° C. | 51.3° F. 10.7° C. | 51.3° F. 10.7° C. |
The difference is not great. For Stockholm the winter has grown warmer, the autumn colder, for London the winter warmer and so slightly also the summer, but spring and autumn a trifle colder, and for Paris the summer a little warmer while the autumn is considerably colder. Lund shows the least variation. The winter has grown 0.4° C. (0.72° F.) warmer and the summer colder by the same amount. The annual mean remains nearly constant, only slightly increased, but the climate is become more marine. (This is hardly apparent from the figures cited as far as Paris is concerned.)
From Tycho Brahe’s observations of the number of days when snow or rain fell in the place where his observatory was situated on the island Hven in Öresund not far from Copenhagen, Ekholm has calculated that the temperature there during the time 1582–1597 was 1.4° C. (2.5° F.) lower in February and 1° C. (1.8° F.) lower in March than in later years (1881–1896). On the other hand the first autumn frost occurred at the same time as now and the same was the case with the last frost in spring, so that the temperatures on these dates in autumn and spring were nearly identical at the end of the sixteenth century and now. Ekholm drew the conclusion that the climate is become more marine.