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Cultural Responses to Climate Change: Lessons from the Past

Cultural Responses to Climate Change: Lessons from the Past. Climate - Society Theories. “Cultural Determinism” Culture alone determines culture. Prevalent throughout 18th-19th century Europe “Environmental determinism” Human culture is determined by the environment. The Land is Sacred

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Cultural Responses to Climate Change: Lessons from the Past

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  1. Cultural Responses to Climate Change: Lessons from the Past

  2. Climate - Society Theories “Cultural Determinism” • Culture alone determines culture. • Prevalent throughout 18th-19th century Europe “Environmental determinism” • Human culture is determined by the environment. • The Land is Sacred “Possiblism” • Compromise: The natural environment influences the range of available (possible) human choices.

  3. Premise • Water availability is the critical factor regulating life in semiarid environments. • Cultures can and do adapt to interannual to decadal changes in climate. • How have cultures responded to longer-term (decade to century-scale) changes? Combine detailed and well-dated paleoclimate and archeological records to search for correlations. Need good age dating to do this reliably.

  4. What do we know about the climate of the last 1,000 years? • Instrumental climate records are too short (100-200 years). • Longer records of past climate change (paleoclimate): • Glaciers • tree rings • corals • lake and ocean sediments • Generally speaking Tree Ring Data is the most robust indicator

  5. Tree-ring record of drought in the American SW wet dry

  6. Excellent Data Set - lots of variability Colorado River Over Allocation

  7. The 1930s Dust Bowl • Six year drought (1933-1938), well-documented. • Due to wanton farming practices and over-capitalization. • Cost over $1 billion in 1930’s dollars, federal relief programs. • US was better prepared for a longer drought in 1950s.

  8. Sea Surface Temperature Anomaly 1932-1939 OBSERVED Contour interval = 0.2°C A cold, La Nina-like, tropical Pacific Ocean

  9. The Dust Bowl Precipitation Anomaly (1932-1939) OBSERVED GOGA MODEL Contour interval = 2 mm/month GOGA MODEL = Global Sea Surface Temperature Specified

  10. What about BEFORE the instrumental record?Tree ring evidence for drought Thickness of tree rings in some species is sensitive to rainfall. Narrow band = dry climate

  11. A Longer Perspective on Drought: Tree Ring Reconstructions Past droughts have been longer and more severe Cook et al., Science (2004)

  12. Medieval Droughts 30 years Similar pattern as modern drought. Conditions persisted MUCH longer(20-40yrs) 40 years 25 years 22 years ‘Mega-droughts’

  13. Drought and the Anasazi (ancestral Pueblo) Classic example of cultural impacts of climate change. Studies of the Four Corners region show population crashes related to megadroughts Number of habitation sites Benson et al. (2006)

  14. Anasazi depopulation of the SW US The “Great Drought” spanned 1272-1298 AD (~26 years). Other factors: Warfare, balkanization, religion. Mesa Verde, CO

  15. Interannual-Decadal Variability • Severe droughts lasting decades are common (many per millennium). • This mode of climate variability is present in the instrumental record (that is, expected). • Cultures can and do readily adapt to these variations. Is this the full range of natural climate variability at socially-relevant timescales?

  16. Mechanisms of Climate Change • Long-term: Earth orbital variations (millennia) • Shorter-term: Solar variability, volcanic eruptions and greenhouse gases (century-scale) • Ocean-atmosphere interactions (El-Niño, NAO…) • Natural, unforced variability (random) • Human Activities • Bottom line – most any regional climate is “unstable” on time scales of 50—100 years

  17. The Little Ice Age and Medieval Warm Period are examples of climate instability Most of the variability over the past 1000 years due to solar variability and volcanism.

  18. Cultural Responses to Climate Change • Paleoclimate records document large climate changes which persisted for many centuries to millennia. • Climate transitions can be very abrupt. • Regional to global (?) extent. • What impact did these climate perturbations have on complex societies living at the time? • Examples: • Akkadian Empire (ca. 4200 yrs BP) • Classic Maya Empire (ca. 1200 yrs BP)

  19. Akkadian Imperial Collapse (4200 yrs BP) • First empire imperialized Mesopotamia between 4300-4200 yr BP. • Imperialization linked productive rainfed (semiarid) agriculture of northern Mesopotamia (Sumer) with south. • Collapse occurred near 4170±150 yr BP (Weiss et al., 1993). • Collapse was previously attributed to political disintegration. Sargon ofAkkad

  20. Tell Leilan, NE Syria • Weiss et al. (1993) excavated this former Akkadian imperial town. • Their results suggested rapid abandonment due to onset of aridity. • At right, a ~600m2 excavated residential occupation with roadway.

  21. Deep-Sea Sediment Record of Mesopotamian Climate Cullen et al. (2000) tested the Weiss et al. (1993) claim using the deep-sea sediment record to reconstruct changes in Mesopotamian climate. • Aridity record should be preserved in deep-sea sediments.

  22. Mesopotamian Dust Dust storm over Mesopotamia (May, 2000) Same dust storm, 10 days later, over the Gulf of Oman

  23. Climate Change and Akkadian Collapse Cullen et al. (2000)

  24. Akkadian Collapse • Onset of ~300 year period of greatly increased aridity near 4025±125 yr BP coincides with Akkadian collapse at 4170±150 yr BP (within dating uncertainty). • How widespread was the collapse? • Enhanced aridity at this time also reported for Turkey, Israel, and Egypt. • Nd and Sr isotopes confirm dust is from a Mesopotamian source similar to Tell Leilan. • Volcanic glass shards found at Tell Leilan and in the deep-sea are geochemically correlative.

  25. Classic Maya Culture (300-900 AD) Classic Maya culture ruled Mesoamerica from 250 to 850 AD. Late Classic culture (550-850 AD) known for highly stratified society, vast trade networks, and widespread construction of urban centers and monumental stellae. 8-15 million people across Yucatan Peninsula Tikal (Guatemala)

  26. Classic Maya Collapse (800 AD) Classic Maya empire collapsed at peak intellectual and cultural development at 900 AD. Lowland urban abandonment End of monument construction Cultural disintegration Factors cited: Deforestation, overpopulation, warfare, religious and social upheaval. Largest urban center: Palenque Scientific Analysis now strongly suggests drought as the main cause.

  27. Cariaco Basin (Venezuela) Annual laminations (sediment deposits)

  28. Climate Change and Classic Maya Collapse Cariaco Basin laminated sediments Mayan collapse occurred during a 150-year drought with four prominent phases wet dry 0 1 2

  29. What can be learned from these examples? Complex societies are sensitive to climate change. Relatively immobile cultures can clearly be adversely effected by long term climate change, specifically long term droughts. - Paleoclimate records document changes in climate Collapse occurred despite evidence that these cultures had large buffering capacities (something Jared Diamond does not adequately consider)

  30. 2002 Modern Lake Powell 2003

  31. Lake Powell levels, today

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