This chapter will relate the development of the neo-deterministic paradigm and paint a canvas of the climatological, hydrological, and historical setting of the Near East. The resulting picture should facilitate an understanding of the interaction between the physical geographical character of this region and its human history – an interaction owed to the region’s situation in a transition zone between two global climatic belts.
The cyclonic rainstorms’ belt of the westerlies and the anti-cyclonic Sahara Desert belt shift annually and multi-annually south and northward, deciding to a great extent the character of the physical environment. This change, as will be demonstrated in the chapters to follow, had a crucial influence on the prosperity and fate of the people living in this region, for better and for worse.
Despite all the advances in technology in the last years, the ultimate rea- sons for many contemporaneous climate phenomena still elude us. For many scientists, the eleven years rhythm of sunspot activity ranks high on the list of primary causes. Others prefer a narrow spacing of volcanic eruptions due to increased tectonic activity. It is perfectly possible that the two phenomena, and possibly others, are somehow interlinked.
One thing has become clear in the last years: Global weather conditions are expressions of the relationship between the atmosphere and the world’s great oceans, with their currents and counter-currents. Two related, but unequal, great systems control our weather. The bigger one, known as the “Southern Oscillation,” is a phenomenon of the tropics with its home province in the world’s largest oceans – the Pacific, the Indian and the southern Atlantic Oceans. As the monsoon and the maverick “El Niño” fall into its “domain of responsibility”, this system, called El Niño-Southern Oscillation, or ENSO, is critically important for most human populations in the tropics.
Table 1.A general historical-archaeological timetable of the Near East for the last 10,000 years
2000
Egypt Syria-Palestine Mesopotamia Anatolia
Mamluk/Ottoman Mamluk/Ottoman Seljuk/Ottoman Seljuk/Ottoman
1000 Early Arab Period Early Arab Period Early Arab Period
C.E. Roman/Byzantine P. Roman/Byzantine P. Parthian/Sassanian Roman/Byzantine P.
B.C.E.
Ptolemaic Period Persian/Hellenistic P. Persian/Hellenistic Persian/Hellenistic
1000
Late Period Iron Age II Asyyrian/Neo-Babylon Iron Age
Iron Age I
New Kingdom Middle/Late Bronze Age Old/Middle Babylonian Middle/Late Bronze 2000 Middle Kingdom Intermediate Bronze Age
Akkad/Ur III/Isin
Old Kingdom Early Bronze Age II/II Early Dynastic I–III Early Bronze Age
3000 Early Bronze Age I Jemdet Nasr
Archaic Period Mature Chalcolithic Gawra (N)/Uruk (S) Late Chalcolithic 4000 Pre Dynastic Period
Early Chalcolithic Ubaid (N & S) Middle Chalcolithic
5000 Early Chalcolithic
Neolithic Period
Pottery Neolithic A/B Halaf (N)/Ubaid (S) Ceramic Neolithic
6000 Early Ceramic
Pre-Pottery Neolithic B Hassuna/Samarra (north only)
Neolithic 7000
Various Epi-Paleolithic
Cultures Pre-Pottery Neolithic A Pre-Pottery Neolithic (north only)
Aceramic Neolithic
Natufian Epi-Paleolithic
Epi-Paleolithic:Kebaran
Period
The other system is the “North Atlantic Oscillation” (NAO). Although smaller, this system has as great an effect and is even more complex than ENSO. NAO is directly responsible for the weather in the Mediterranean re- gion, as on the border between it and ENSO, the “Inter-tropical Convergence Zone” (ITCZ) has formed. The constantly fluctuating and even volatile interac- tion between these two global systems is largely responsible for the formation and subsequent increase or decrease of the desert belt ranging from northern Africa via the Near East to central Asia and Mongolia.1
Because of the importance of the North Atlantic Oscillation as the origin of the westerly winds bringing rain to the Near East, let us briefly remind the reader of itsmodus operandi. Sir Gilbert Walker coined the term in the 1920’s based on his observations of interrelations between the low pressure near Iceland and the high pressure near the Azores.2It is supported by the Gulf
1M. Glantz,Currents of Change: El Niño’s Impact on Climate and Society, Cambridge University Press, Cambridge, UK (1996).
W.S. Broecker and G.H. Denton, “What Drives Climatic Cycles?”Scientific American, 262/1:49–56 (1990).
R. Kandel,Water from Heaven, Columbia University Press, NY pp. 101–123 (2003).
2G. Walker, “Correlations in Seasonal Variations of Weather IX”India Meteorological Department Memoirs24/9 (1924).
Stream carrying warm and salty water from the Caribbean Sea northeast along the eastern shores of northern America and then across the northern Atlantic.
Before reaching the coasts of Europe, the stream splits into two. A southern current passes the coasts of Portugal, the Azores and northern Africa, and then rejoins the northern Brazil Current and heads back to the Caribbean Sea.
The northern branch continues in a northeasterly direction as the North Atlantic Current until Spitzbergen, the Barents Sea, and the Arctic Basin.
South of Iceland, some of the warm waters turn west, drawn by the cold East Greenland Current, which runs along the eastern shores of Greenland from the northwest to the southeast and into the Labrador Sea. There, they join another cold flow from the north, the Labrador Current, famous for its many floating icebergs due to the increase of warmer water.
The Gulf Stream-North Atlantic Current warms western and northern Eu- rope. The bulk of this salty, and therefore heavier water, eventually sinks deep into the ocean where it joins the deep “Great Ocean Conveyor Belt” on its way south. It is this sinking and down-welling of the salty waters that keeps the circulation of the Gulf Stream in motion. Any disturbance, such as abnormal dilution of the salty waters by melting waters from the northern ice, or other influence on the mechanism that might slow down or even stop the sinking would have enormous consequences on the oscillation between the Atlantic
‘highs’ and ‘lows’ and on the fluctuation of the jet stream bringing rain to the western Mediterranean area. If this proves to be correct, the melting of the Arctic ice cap observed in 1999/2000 might slow down the sinking of the Gulf Stream and in its wake bring colder weather to Europe and the Near East over the next few years. On the other hand, Issar’s investigations have shown that global warming causes warming and drying of the Mediterranean region.
Thus, a severe downward fluctuation of temperatures may be just the first stage of the general trend of warming and drying if at all, as stronger climatic forces may nullify it.Other elements in the general picture are the jet streams, fast moving air currents at high altitudes. The polar jet influences the climate over the Mediterranean, flowing from west to east and changing its position from north to south according to the seasons.
While it is clear that the interplay among these factors determines contem- porary changes of climate within the seasonal range and a range of a couple of years, the question remains as to what could have caused the changes of climate in the range of historical periods, from a few decades to a few centuries and even a few millennia. The driving force may have been similar to that responsible for the other changes during the Quaternary, including the glacial and interglacial periods. It is beyond the scope of this work to detail the cause and effects of the global glaciations and de-glaciations that occurred during the Quaternary. The reader who is interested in this subject is advised to consult the list of references.3
3J. and K.P. Imbrie,Ice Ages – Solving the Mystery. Macmillan, London (1979).
A. Berger, R.E. Dickinson, J.W. Kidson, “Understanding Climate Change”,Geophysical Monographs 52, IUGG Volume 7, A.G.U. Washington, DC (1989).
R.S. Bradley, “Palaeoclimatology. Reconstructing Climates of the Quaternary”,International Geo- physics series, 2nd ed., vol. 64, Academic Press, San Diego, USA, pp. 11–46 (1999).
In brief, however, the glacial and interglacial phenomena of the Pleistocene portion of the Quaternary are due primarily to the obliquity of the Earth’s axis and variations in its orbit of the sun. In 1941, the Serbian astronomer Milankovitch calculated the minimum values of radiation due to minimum obliquity of Earth’s bipolar axis and high eccentricity of its orbit around the sun and proposed that this was the reason for glaciations phenomena dur- ing the Quaternary.4 The time spans for these occurrences were calculated at 185,000 years, 115,000 and 70,000 years. Later investigations, based on in- terpretation of the isotopic composition of marine microfossils taken from sea bottom cores, confirmed Milankovitch’s general calculations, but specified the periodicity around 100,000, 41,000 and 19,000 to 23,000 years. Thus Mi- lankovitch’s theory does explain climate cyclic and long-term fluctuations in the order of magnitude of hundreds of thousands to a few tens of thousands of years. However, in the case of forces responsible for short-term climate changes within a few millennia, centuries or decades, different factors seem to be at work. These may be sunspots, which affect levels of solar radiation, or volcanic explosions, which have a negative effect on the transparency of the atmosphere.
High temperatures, on the other hand, are sometimes associated with years of major El-Niño events, which are minimized when volcanic explosions occur during these years.5The possibility that volcanic explosions may have played an important role in the climate changes of the Holocene was brought up by Issar as a working hypothesis.6