4.2 kiloyear event
The 4.2 kiloyear BP aridification event was one of the most severe climatic events of the Holocene period. Starting in about 2200 BC, it probably lasted the entire 22nd century BC. It has been hypothesised to have caused the collapse of the Old Kingdom in Egypt as well as the Akkadian Empire in Mesopotamia, and the Liangzhu culture in the lower Yangtze River area. The drought may also have initiated the collapse of the Indus Valley Civilization, and southeastward habitat tracking of its population, as well as the migration of Indo-European speaking people into India.
A phase of intense aridity about 4.2 ka BP is recorded across North Africa, the Middle East, the Red Sea, the Arabian peninsula, the Indian subcontinent, and midcontinental North America. Glaciers throughout the mountain ranges of western Canada advanced at about this time. Evidence has also been found in an Italian cave flowstone, the Kilimanjaro Ice sheet, and in Andean glacier ice. The onset of the aridification in Mesopotamia about 4100 BP also coincided with a cooling event in the North Atlantic, known as Bond event 3. Despite this, evidence for the 4.2 kyr event in northern Europe is ambiguous, suggesting the origin and impact of this event is spatially complex.
According to Moreno et al., who reported the first palaeohydrogeological interdisciplinary research in La Mancha, Spain,
Recent studies show that the "motilla" sites from the Bronze Age in La Mancha may be the most ancient system of groundwater collection in the Iberian Peninsula.... These were built during the Climatic Event 4.2 ka cal BP in a time of environmental stress due to a period of severe, prolonged drought.
The authors' analysis verified a relationship between the geological substrate and the spatial distribution of the motillas.
In c. 2150 BC, the Old Kingdom was hit by a series of exceptionally low Nile floods. It has been suggested that may have impacted the collapse of the centralised government in ancient Egypt. Contemporary texts claim that famines, social disorder and fragmentation subsequently occurred. There may however be a strong element of political bias to these writings since the Egyptian elite believed the stability of Egypt was dependent on a unified state, and they would have been motivated to present decentralisation as disastrous. After a phase of rehabilitation and restoration of order in various provinces, Egypt was eventually reunified within a new paradigm of kingship. The process of recovery depended on capable provincial administrators, a more formalised justice system, irrigation projects, and an administrative reform.
In the Persian Gulf region, there is a sudden change in settlement pattern, style of pottery and tombs at this time. The 22nd century BC drought marks the end of the Umm an-Nar Culture and the change to the Wadi Suq period.
The aridification of Mesopotamia may have been related to the onset of cooler sea-surface temperatures in the North Atlantic (Bond event 3), as analysis of the modern instrumental record shows that large (50%) interannual reductions in Mesopotamian water supply result when subpolar northwest Atlantic sea surface temperatures are anomalously cool. The headwaters of the Tigris and Euphrates Rivers are fed by elevation-induced capture of winter Mediterranean rainfall.
The Akkadian Empire, in 2300 BC, was the second civilization to subsume independent societies into a single state (the first being ancient Egypt around 3100 BC). It has been claimed that the collapse of the state was influenced by a wide-ranging, centuries-long drought. Archaeological evidence documents widespread abandonment of the agricultural plains of northern Mesopotamia and dramatic influxes of refugees into southern Mesopotamia, around 2170 BC. A 180-km-long wall, the "Repeller of the Amorites," was built across central Mesopotamia to stem nomadic incursions to the south. Around 2150 BC, the Gutian people, who originally inhabited the Zagros Mountains, defeated the demoralised Akkadian army, took Akkad, and destroyed it around 2115 BC. Widespread agricultural change in the Near East is visible at the end of the 3rd millennium BC.
Resettlement of the northern plains by smaller sedentary populations occurred near 1900 BC, three centuries after the collapse.
South central Asia and IndiaEdit
In the second century BCE widespread aridization lead to water shortages and ecological changes in both the Eurasian steppes and south Asia. At the steppes, humidization lead a change of vegetation, triggering "higher mobility and transition to the nomadic cattle breeding."[note 1][note 2] Water shortage also had a strong impact in south Asia:
This time was one of great upheaval for ecological reasons. Prolonged failure of rains caused acute water shortage in a large area, causing the collapse of sedentary urban cultures in south central Asia, Afghanistan, Iran, and India, and triggering large-scale migrations. Inevitably, the new arrivals came to merge with and dominate the post-urban cultures.
The drought may have initiated southeastward habitat tracking within the Indus Valley Civilization. The Indus Valley Civilisation was localised, that is, urban centers disappeared and were replaced by local cultures, due to a climate change that is also signalled for the neighbouring areas of the Middle East. As of 2016[update] many scholars believe that drought and a decline in trade with Egypt and Mesopotamia caused the collapse of the Indus Civilisation. The Ghaggar-Hakra system was rain-fed, and water-supply depended on the monsoons. The Indus valley climate grew significantly cooler and drier from about 1800 BCE, linked to a general weakening of the monsoon at that time. The Indian monsoon declined and aridity increased, with the Ghaggar-Hakra retracting its reach towards the foothills of the Himalaya, leading to erratic and less extensive floods that made inundation agriculture less sustainable. Aridification reduced the water supply enough to cause the civilisation's demise, and to scatter its population eastward.
The drought may have caused the collapse of Neolithic Cultures around Central China during the late third millennium BC. At the same time, the middle reaches of the Yellow River saw a series of extraordinary floods. In the Yishu River Basin, the flourishing Longshan culture was hit by a cooling that made the paddies shortfall in output or even no seeds were gathered. The scarcity in natural resource led to substantial decrease in population and subsequent drop in archaeological sites. In about 2000 BC, Longshan was displaced by the Yueshi culture, which was relatively underdeveloped.
- Demkina et al. (2017): "In the second millennium BC, humidization of the climate led to the divergence of the soil cover with secondary formation of the complexes of chestnut soils and solonetzes. This paleoecological crisis had a significant effect on the economy of the tribes in the Late Catacomb and Post-Catacomb time stipulating their higher mobility and transition to the nomadic cattle breeding."
- See also Eurogenes Blogspot, The crisis.
- deMenocal, Peter B. (2001). "Cultural Responses to Climate Change During the Late Holocene". Science. 292 (5517): 667–673. Bibcode:2001Sci...292..667D. PMID 11303088. doi:10.1126/science.1059827.
- Gibbons, Ann (1993). "How the Akkadian Empire Was Hung Out to Dry". Science. 261 (5124): 985. Bibcode:1993Sci...261..985G. PMID 17739611. doi:10.1126/science.261.5124.985.
- Staubwasser, M.; et al. (2003). "Climate change at the 4.2 ka BP termination of the Indus valley civilization and Holocene south Asian monsoon variability". Geophysical Research Letters. 30 (8): 1425. Bibcode:2003GeoRL..30h...7S. doi:10.1029/2002GL016822.
- Rajesh Kochhar (2017), The Aryan chromosome, The Indian ERxpress
- Gasse, Françoise; Van Campo, Elise (1994). "Abrupt post-glacial climate events in West Asia and North Africa monsoon domains". Earth and Planetary Science Letters. 126 (4): 435–456. Bibcode:1994E&PSL.126..435G. doi:10.1016/0012-821X(94)90123-6.
- Bar-Matthews, Miryam; Ayalon, Avner; Kaufman, Aaron (1997). "Late Quaternary Paleoclimate in the Eastern Mediterranean Region from Stable Isotope Analysis of Speleothems at Soreq Cave, Israel". Quaternary Research. 47 (2): 155–168. Bibcode:1997QuRes..47..155B. doi:10.1006/qres.1997.1883.
- Arz, Helge W.; et al. (2006). "A pronounced dry event recorded around 4.2 ka in brine sediments from the northern Red Sea". Quaternary Research. 66 (3): 432–441. Bibcode:2006QuRes..66..432A. doi:10.1016/j.yqres.2006.05.006.
- Parker, Adrian G.; et al. (2006). "A record of Holocene climate change from lake geochemical analyses in southeastern Arabia" (PDF). Quaternary Research. 66 (3): 465–476. Bibcode:2006QuRes..66..465P. doi:10.1016/j.yqres.2006.07.001. Archived from the original (PDF) on October 29, 2008.
- Booth, Robert K.; et al. (2005). "A severe centennial-scale drought in midcontinental North America 4200 years ago and apparent global linkages". The Holocene. 15 (3): 321–328. doi:10.1191/0959683605hl825ft.
- Menounos, B.; et al. (2008). "Western Canadian glaciers advance in concert with climate change c. 4.2 ka". Geophysical Research Letters. 35 (7): L07501. Bibcode:2008GeoRL..3507501M. doi:10.1029/2008GL033172.
- Drysdale, Russell; et al. (2005). "Late Holocene drought responsible for the collapse of Old World civilizations is recorded in an Italian cave flowstone". Geology. 34 (2): 101–104. Bibcode:2006Geo....34..101D. doi:10.1130/G22103.1.
- Thompson,L.G; et al. (2002). "Kilimanjaro Ice Core Records Evidence of Holocene Climate Change in Tropical Africa". Science. 298: 589–93. Bibcode:2002Sci...298..589T. PMID 12386332. doi:10.1126/science.1073198.
- Davis, Mary E.; Thompson, Lonnie G. (2006). "An Andean ice-core record of a Middle Holocene mega-drought in North Africa and Asia" (PDF). Annals of Glaciology. 43: 34–41. Bibcode:2006AnGla..43...34D. doi:10.3189/172756406781812456. Archived from the original (PDF) on July 11, 2007.
- Bond, G.; et al. (1997). "A Pervasive Millennial-Scale Cycle in North Atlantic Holocene and Glacial Climates" (PDF). Science. 278 (5341): 1257–1266. Bibcode:1997Sci...278.1257B. doi:10.1126/science.278.5341.1257. Archived from the original (PDF) on 2008-02-27.
- "Two examples of abrupt climate change". Lamont-Doherty Earth Observatory. Archived from the original on 2007-08-23.
- Roland, Thomas P; et al. (2014). "Was there a ‘4.2 ka event’ in Great Britain and Ireland? Evidence from the peatland record". Quaternary Science Reviews. 83: 11–27. Bibcode:2014QSRv...83...11R. doi:10.1016/j.quascirev.2013.10.024.
- Mejías Moreno, M., Benítez de Lugo Enrich, L., Pozo Tejado, J. del y Moraleda Sierra, J. 2014. Los primeros aprovechamientos de aguas subterráneas en la Península Ibérica. Las motillas de Daimiel en la Edad del Bronce de La Mancha. Boletín Geológico y Minero, 125 (4): 455–474 ISSN 0366-0176
- Stanley, Jean-Daniel; et al. (2003). "Nile flow failure at the end of the Old Kingdom, Egypt: Strontium isotopic and petrologic evidence". Geoarchaeology. 18 (3): 395–402. doi:10.1002/gea.10065.
- Cullen, Heidi M.; deMenocal, Peter B. (2000). "North Atlantic influence on Tigris-Euphrates streamflow". International Journal of Climatology. 20 (8): 853–863. Bibcode:2000IJCli..20..853C. doi:10.1002/1097-0088(20000630)20:8<853::AID-JOC497>3.0.CO;2-M.
- Kerr, Richard A. (1998). "Sea-Floor Dust Shows Drought Felled Akkadian Empire". Science. 279 (5349): 325–326. Bibcode:1998Sci...279..325K. doi:10.1126/science.279.5349.325.
- Weiss, H; et al. (1993). "The Genesis and Collapse of Third Millennium North Mesopotamian Civilization". Science. 261 (5124): 995–1004. Bibcode:1993Sci...261..995W. PMID 17739617. doi:10.1126/science.261.5124.995.
- Riehl, S. (2008). "Climate and agriculture in the ancient Near East: a synthesis of the archaeobotanical and stable carbon isotope evidence". Vegetation History and Archaeobotany. 17 (1): 43–51. doi:10.1007/s00334-008-0156-8.
- Demkina 2017.
- "Decline of Bronze Age 'megacities' linked to climate change".
- "Indus Collapse: The End or the Beginning of an Asian Culture?". Science Magazine. 320: 1282–3. 6 June 2008.
- Giosan, L.; et al. (2012). "Fluvial landscapes of the Harappan Civilization". Proceedings of the National Academy of Sciences USA. 109 (26).
- Clift et al., 2011, U-Pb zircon dating evidence for a Pleistocene Sarasvati River and capture of the Yamuna River, Geology, 40, 211–214 (2011). 
- Tripathi, Jayant K.; Tripathi, K.; Bock, Barbara; Rajamani, V. & Eisenhauer, A. (25 October 2004). "Is River Ghaggar, Saraswati? Geochemical Constraints" (PDF). Current Science. 87 (8).
- Rachel Nuwer (28 May 2012). "An Ancient Civilization, Upended by Climate Change". LiveScience. Retrieved 29 May 2012.
- Charles Choi (29 May 2012). "Huge Ancient Civilization's Collapse Explained". New York Times. Retrieved 18 May 2016.
- Madella, Marco; Fuller, Dorian (2006). "Palaeoecology and the Harappan Civilisation of South Asia: a reconsideration". Quaternary Science Reviews. 25 (11–12): 1283–1301. Bibcode:2006QSRv...25.1283M. doi:10.1016/j.quascirev.2005.10.012.
- MacDonald, Glen (2011). "Potential influence of the Pacific Ocean on the Indian summer monsoon and Harappan decline". Quaternary International. 229: 140–148. Bibcode:2011QuInt.229..140M. doi:10.1016/j.quaint.2009.11.012.
- Brooke, John L. (2014), Climate Change and the Course of Global History: A Rough Journey, Cambridge University Press, p. 296, ISBN 978-0-521-87164-8
- Wu, Wenxiang; Liu, Tungsheng (2004). "Possible role of the "Holocene Event 3" on the collapse of Neolithic Cultures around the Central Plain of China". Quaternary International. 117 (1): 153–166. Bibcode:2004QuInt.117..153W. doi:10.1016/S1040-6182(03)00125-3.
- Chun Chang Huang; et al. (2011). "Extraordinary floods related to the climatic event at 4200 a BP on the Qishuihe River, middle reaches of the Yellow River, China". Quaternary Science Reviews. 30 (3–4): 460–468. Bibcode:2011QSRv...30..460H. doi:10.1016/j.quascirev.2010.12.007.
- Gao, Huazhong; Zhu, Cheng; Xu, Weifeng (2007). "Environmental change and cultural response around 4200 cal. yr BP in the Yishu River Basin, Shandong". Journal of Geographical Sciences. 17 (3): 285–292. doi:10.1007/s11442-007-0285-5.
- Demkina, T.S. (2017), "Paleoecological crisis in the steppes of the Lower Volga region in the Middle of the Bronze Age (III–II centuries BC)", Eurasian Soil Science, July 2017, Volume 50, Issue 7, pp 791–804