NOAA/IPRC Workshop on Climatic Changes in the Last 1500 Years: Their Impacts on Pacific Islands, East-West Center, 13th November 2007 A Shock to the System: Climatic Disruption of Pacific Island Societies around AD 1300

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NOAA/IPRC Workshop onClimatic Changes in the
Last 1500 YearsTheir Impacts on Pacific
Islands, East-West Center, 13th November 2007A
Shock to the SystemClimatic Disruption of
Pacific Island Societies around AD 1300

• Patrick D. Nunn
• Professor of Oceanic Geoscience
• The University of the South Pacific

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Climate, Environment and Society

• Climatic change produces environmental change.

Channelled scablands, NW USA
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Climate, Environment and Society

• Climatic change produces environmental change.
• Both climatic and environmental changes can
  profoundly affect human societies.

Fiji floods, 2004 courtesy Fiji Times
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Climatic Influences on Environmentsinsights
from high-resolution data series
Solar irradiance (14C) and sea-level change at
Farm River Marsh, NE USA
Source van de Plassche et al. (2003 Geology
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Climatic Influences on Environmentsan empirical
study from the Pacific
Source Razjigaeva et al., 2004 Palaeo3
Kurile Islands, Northwest Pacific Ocean
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Climatic Influences on Human Society general
considerations

• Environmental determinism versus cultural
  determinism.
• Emerging acceptance of the potential of climatic
  change to force changes in pre-modern human
  societies.
• Watershed studies

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Climatic Influences on Human Society watershed
studies from the Pacific
Direct influence of climate on society Source
Titanium (precipitation proxy), Cariaco Basin,
Venezuela, and its effects on Maya civilization
in central America (Haug et al., 2001 Science)
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Climatic Influences on Human Societywatershed
studies from the Pacific
Climate influence on society through
environmental filter
Source William R. Dickinson
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Island societies are good case studies because
their societies often register an amplified
response to climate forcing.

• Why?
• Relative smallness.
• Relative isolation.
• Relative homogeneity of environments and
  societies.

Necker Island, Hawaii Islands
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The Pacific Basin
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Volcanic Pacific Islands
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Limestone Pacific Islands
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Pacific Island paleoclimate archives
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History of human settlement of the Pacific Islands
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Organization of this talk

1. Last-millennium climate change in the Pacific
2. Environmental changes on tropical Pacific Islands
   during the last millennium
3. Societal changes on tropical Pacific Islands
   during the last millennium
4. Possible climate forcing of last-millennium
   environmental and societal change in the tropical
   Pacific Islands the AD 1300 Event

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Part 1Last-millennium climate change in the
Pacific
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Last-millennium climate changes in the Pacific
summary

• Medieval Warm Period (ca. AD 750-1250),
  comparatively warm dry climate with high sea
  level.
• AD 1300 Event (ca. AD 1250-1350), rapid cooling,
  increased precipitation, falling sea level.
• Little Ice Age (ca. AD 1350-1800), comparatively
  cool climate, higher climate variability
  (increased El Niño frequency), low sea level.
• Recent Warming (ca. AD 1800-present), warming,
  reduced climate variability, rising sea level.

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Ice coring tropical Andes Thompson et al., 2003
Climatic Change
Medieval Warm Period comparative
warmth Little Ice Age
comparative coolness Recent Warming -
increasing warmth
(transition) AD 1300 Event cooling
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Compilation from Nunn (2007) book
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Westernmost USA, Nevada dendrochronology (Hughes
and Graumlich, 1996 book chapter) and lake-level
data
Medieval Warm Period comparatively dry Little
Ice Age comparatively wet
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Stalagmite, Buddha Cave, east China (Paulsen et
al., 2003 Quaternary Science Reviews.
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El Niño frequency change

1. Laguna Pallcacocha, Ecuador
2. Laguna Aculeo, Chile
3. Sacramento River, USA
4. Historical records

Compilation from Nunn (2007) book
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Pacific Islands compilation
Compilation from Nunn (2007) book
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Last-millennium climate changes in the Pacific
the AD 1300 Event

• Too much emphasis hitherto on discrete periods
  rather than transitions as the causes of
  environmental and societal change.
• The AD 1300 Event was the most rapid period of
  climatic change within the past few thousand
  years.

Source Dahl-Jensen et al., 1998 Science
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Part 2Environmental changes on tropical Pacific
Islands during the last millennium
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Qaranilaca (Sail Cave), Vanuabalavu Island, Fiji
Anthropogenic cave fill
Storm-wave deposit

• No sign of cave occupation during Medieval Warm
  Period (cave flooded?)
• Fill begins accumulating about AD 1400 (sea level
  has fallen?)
• Transient cave occupation begins about AD 1450
  during Little Ice Age (sea level low)
• Cave fill now being eroded (sea level rising)

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Kawai Nui wetland, Oahu Island, Hawaii

• During Medieval Warm Period, Kawai Nui was an
  ocean bay (sea level high)
• During Little Ice Age, Kawai Nui became a
  brackish-water swamp (sea level low)

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Tikopia Island, eastern outer Solomon Islands
Original research Kirch and Yen (1982)
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Ravenga Tombolo
1833 lithograph by Louis Auguste de Sainson
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Part 3Societal changes on tropical Pacific
Islands during the last millennium

1. settlement-pattern change and the emergence of
   conflict
2. end of cross-ocean interaction

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Easter Island (Rapanui)

• Colonized about AD 690 (maybe AD 1200)
• AD 1300, conflict begins, statue-making frenzy

mataa obsidian spearheads
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Tatuba Cave
Dates for the establishment of hillforts and
fortified caves in the Sigatoka Valley, Viti Levu
Island, Fiji (courtesy of Dr Julie Field)
Korokune hillfort
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Tatuba Cave
Korokune hillfort
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Changing settlement pattern, KauaI Island,
Hawaii during the last millennium
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New Zealand (not tropical!)
Beginning around AD 1300, coastal settlements
were abandoned in favor of fortified hilltop
settlements named pa. Conflict ensued.
The pa at Tolaga about 1780 (Herman Spöring)
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Palau Islands, western tropical Pacific
Babeldaob Island
Rock Islands
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End of cross-ocean interaction
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Part 4Climatic forcing of last-millennium
environmental and societal change in the tropical
Pacific Islands
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Model of the AD 1300 Event

• Climate change drives environmental change
• Environmental change drives societal change
• Climate change also directly drives societal
  change

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One example of societal response to climate
forcing is settlement-pattern change
Warm, moist climate sea level rising
Warm, dry climate sea level high
Cool, variable climate sea level low
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Solar forcing (sunspot numbers) and Pacific
climate change
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Solar forcing and sea-level change in the Pacific
Solar irradiance (?14C) and sea-level change,
Pacific Islands composite (90-year lag) from Nunn
(2007) book.
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Conclusion

• Climate change, both directly and through
  environmental filters, caused profound societal
  changes in the tropical Pacific Islands during
  the last millennium.

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Nunn, P.D. 2007. Climate, Environment and Society
in the Pacific during the Last Millennium.
Amsterdam Elsevier, 316 p. Nunn, P.D. 2007. The
AD 1300 Event in the Pacific Basin overview and
teleconnections. The Geographical Review, 97,
1-23. Nunn, P.D. 2007. Holocene sea-level change
and human response in Pacific Islands. Earth and
Environmental Science, 98, 117-125. Nunn, P.D.,
Hunter-Anderson, R., Carson, M.T., Thomas, F.,
Ulm, S. and Rowland, M. 2007. Times of plenty,
times of less chronologies of last-millennium
societal disruption in the Pacific Basin. Human
Ecology An Interdisciplinary Journal, 35,
385-402. Thank you for your attention.