Transcript Cultural Responses to Climate Change: Lessons from the Holocene

Lecture 4-2
Cultural Responses to Climate Change:
Lessons from the Holocene
• 8000-4000多年前的全新世温暖期，是近万年来
的最暖时期，全球各地的温度比现在高2-5摄氏
度。那个时期的地球远比现在暖湿，人类生存条
件奇佳，人类的发展出现飞跃，埃及文明﹑两河
流域文明﹑印度河流域文明和中国黄河文明相继
诞生，人类从此进入文明社会。这段时期也被古
气候学家称为“人类最适宜气候期”。
• 在距今4000-3700年和距今3100-2900年，及17世
纪附近，有过三次千年尺度的寒冷期，出现了严
重的低温冷害﹑洪涝﹑乾旱﹑沙漠化灾害，造成
印度河文明在3900年前突然湮灭﹑环地中海文明
在三千年前衰落等悲剧的出现
• Native global flood stories are documented as history
or legend in almost every region on earth
• Old world missionaries reported their amazement at
finding remote tribes already possessing legends with
tremendous similarities to the Bible's accounts of the
worldwide flood
• Ancient civilizations such as (China, Babylonia,
Wales, Russia, India, America, Hawaii, Scandinavia,
Sumatra, Peru, and Polynesia) all have their own
versions of a giant flood
(1271- 1368)
1110 – 1190
(960 - 1127)
( 780 - 920
)
420-589
)
)
年
）
温 寒
暖 冷
年
) ( 570-770
公
元
-
(
南
北
朝
年
元
朝
北 南
宋 宋
时 （
期
唐
后
期
寒
冷
期
隋
盛
唐
近1000 年来气候旱涝
变化周期的缩短与朝
代演替频率的加快
Climate - Society Theories
“Cultural Determinism”:the culture in which we are
raised determines who we are at emotional and
behavioral levels
– Culture alone determines culture.
– Prevalent throughout 18th-19th century Europe
“Environmental determinism”
– Human culture is determined by the environment.
• Charles Darwin “Origin of Species”, 1870’s
“Possiblism”
– Compromise: The natural environment influences the
range of available (possible) human choices.
Overview
• Climate of the last 10,000 years (Holocene):
– Punctuated by large and persistent climate
changes every ~1000-2000 years.
• Cultural responses to past climate change:
– The Classic Maya and Akkadian empires.
• We can learn about our future by studying the
past.
Introduction
• 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.
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
Tree-ring record of drought
in the American SW
wet
dry
The 1930s Dust Bowl
• Six year drought (19331938), well-documented.
• Due to wanton farming
practices(肆意耕作实践 )
and over-capitalization.
• Cost over $1 billion in
1930’s dollars, federal
relief programs.
• US was better prepared
for a longer drought in
1950s.
Sea Surface Temperature Anomaly 1932-1939
OBSERVED
Contour interval = 0.2°C
A cold, La Nina-like, tropical Pacific Ocean
La Niña state
Warm water accumulates in far western Pacific.
Equatorial water is cooler than in the normal state
The Dust Bowl Precipitation Anomaly
(1932-1939)
OBSERVED
Contour interval = 2 mm/month
GOGA MODEL
GOGA MODEL = Global Sea
Surface Temperature Specified
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
A Longer Perspective on Drought:
Tree Ring Reconstructions
Past droughts have been longer and more severe
wetter
drier
Cook et al., Science
(2004)
30 years
Medieval Droughts
Similar pattern as modern
drought.
40 years
Conditions persisted MUCH
longer (20-40yrs)
25 years
22 years
‘Mega-droughts’
Drought and the Anasazi (ancestral Pueblo)
Number of habitation sites
Classic example of cultural
impacts of climate change.
Studies of the Four Corners
region show population crashes
related to megadroughts
Benson et al. (2006)
Anasazi depopulation of the SW US
The “Great Drought” spanned
1272-1298 AD (~26
years).
Other factors: Warfare,
balkanization, religion.
Mesa Verde, CO
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?
Holocene Climate
The Holocene represents the present warm
period (last ca. 12,000 years).
It’s “Our Time”, spanning the emergence of
agriculture and civilizations.
– How stable was it?
– What factors influenced Holocene climate
change?
Mechanisms of Holocene 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)
Stable or Unstable Holocene?
Unstable! Persistent 1500±500 year variability
The Little Ice Age and Medieval Warm Period
were the most recent of these events...
Most of the variability over the past 1000 years due to
solar variability and volcanism.
Cultural Responses to Holocene 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)
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.
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.
Deep-Sea Sediment Record of
Mesopotamian Climate
30
40
50
60
40
Tell Leilan
Eu
ris
Tig
Cullen et al. (2000) tested the
Weiss et al. (1993) claim
using the deep-sea sediment
record to reconstruct
changes in Mesopotamian
climate.
ph
ra
tes
30
M5-422
20
Nile
– Late Holocene aridity record
should be preserved in
deep-sea sediments.
10
Dust source areas
Dr. Heidi Cullen
The Weather Channel !
Summer surface winds &
dust transport vectors
Mesopotamian Dust
Dust storm over Mesopotamia (May, 2000)
Same dust storm, 10 days later,
over the Gulf of Oman
Climate Change and Akkadian Collapse
Cullen et al. (2000)
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.
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)
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
Why did this great civilization
fall?
Factors cited: Deforestation,
overpopulation, warfare, religious
and social upheaval.
Largest urban center: Palenque
1. Why did Copán
collapse?
2. Was the end a gradual
decline or a rapid fall?
The spongy-looking
areas at the back of the
skull are caused by a
lack of iron in the diet.
This person suffered
from malnutrition.
80 percent of the
skeletons found at Copán
show evidence of
anemia.
Sociopolitical Causes of Collapse
The sociopolitical
causes include:
 peasant revolts
resulting in the
overthrowing of the
elite class
 inter-site warfare
between Maya citystates
 invasions by peoples
from outside the
Maya civilization
 failure of centralized
political authority
On one of these
unfinished sides, the
Maya text shows a date,
equivalent to February
10, A.D. 822. The
remaining text was
never finished.
There are no known
monuments at Copán
dated after A.D. 822.
Copan sacrificial alter
Natural Causes of Collapse
Natural causes include
factors such as:
 soil exhaustion due to
slash-and-burn
agriculture
 water loss and erosion
of topsoil evident by
increased
sedimentation in lakes
 natural disasters such
as earthquakes and
hurricanes
 climatic change
 disease
 insect infestations
 overpopulation
Copan Great Ball Court
Natural Causes
of Collapse
Water deficit on the Yucatan © NOAA
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When examining the natural causes that could have incited
or enhanced the collapse, a further set of both humaninduced and natural climatic factors of the Yucatan
Peninsula need to be considered
Some scientists theorize that the paleoclimate of the region
was not only different than the present day climate, but that
the natural climatic variability of the past could have
included a period of intense drought that occurred at the
time of the Classic Maya Collapse
Symptoms of the Collapse
Copan East Plaza with Temple of Inscriptions and alter Q; R: Copan East Plaza
and Temple 11 with Popol Nah.
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Rapid depopulation of the countryside and ceremonial
centers in 50 to 100 years,
Abandonment of administrative and residential structures
Symptoms of the
Collapse

Cessation of: building construction,
carving of sculptured monuments,
manufacture of pottery, stonework,
jade carvings, Classic calendar
and writing systems.
Above: Copan temple; Above R: corbeled
block-work used by Maya; lBelow R:
Copan sculpture.
Yucatan Modern Climate
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Before studying the paleoclimate of
the region, it is important to understand
the region's modern climate.
Temperature is uniformly warm on the
Yucatan Peninsula with a mean annual
temperature of 25o C.
Precipitation increases from north to
south with minimum values of 500
mm/yr along the NW coast to a
maximum of 2500 mm/yr in the
southern lowlands.
Rainfall is highly seasonal with the
rainy season occurring in the summer,
May through September, and the dry
season during winter, October through
April.
All of the Yucatan is marked by an
annual water deficit that is lowest in the
southern Yucatan and highest along
the NW coast.
Koeppen Climate classification
© NOAA
Lake Sediments
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The raw material for
paleoenvironmental studies is
sediment that accumulates in an
ordered manner through time and
records changes in past climate
conditions.
The sediments are analogous to a
magnetic cassette tape recording,
and the challenge for
paleoclimatologists is to "play
back" the tape.
Fossil pollen preserved in lake
sediments are often used to
reconstruct vegetation changes
that can be influenced by climate.
Sediment core from Lake
Chichancanab
Lake Sediment Cores
Scientists reconstructed the
past climate of the Maya
civilization by studying lake
sediment cores on the Yucatan
Peninsula.
The first area of study, Lake
Chichancanab, is located in the
center of the Yucatan.
Lake Chichancanab is a long
(26-km), narrow (2 km) lake,
consisting of a series of basins
that are connected during high
water level.
Jason Curtis holding core form Lake
Chichancanab
Lake Chichancanab
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Sediment cores
were collected from
the central basin in
a water depth of 6.9
m.
The lake lies in a
fault depression
caused by normal
faulting. The steep
hills on the eastern
side of the lake
represent the fault
line.
Lake Sediments
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Pollen cannot be used to
reconstruct climate during the
Classic Period because the
Maya severely altered regional
vegetation through clear cutting
of the forest for agricultural
purposes.
It would be impossible to tell,
whether a given vegetation
change was caused by climate
or human agricultural activity.
Because of this, scientists rely
upon geochemical (elemental
and isotopic) evidence for
climatic change found trapped in
the shells of tiny Crustacea
called ostracods.
Oxygen Isotopes
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One of the most important tools used to
reconstruct the ratio of evaporation to
precipitation is oxygen isotopes .
Lake water (H2O) contains both the light
isotope (16O) and heavy isotope (18O) of
the element oxygen.
When water evaporates, the lighter
isotope (H216O) evaporates at a faster
rate than the heavier isotope (H218O)
because it has a higher vapor pressure.
The reverse happens when water
condenses. As long as evaporation
equals precipitation over the lake, the
lake is at a steady state and the ratio of
18O to 16O will be constant.
However, if climate becomes drier and
evaporation exceeds precipitation, the
lake volume will be reduced and the ratio
of 18O to 16O in lake water will increase.
Illustration From Curtis,
et al © 2007
Oxygen Isotopes
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Alternatively, under wet climatic
conditions, the lake level will rise
and the ratio of 18O to 16O will
decrease. In closed basin lakes, the
ratio of 18O to 16O in lake water is
controlled mainly by the balance
between evaporation and
precipitation.
The 18O to 16O ratio of lake water is
recorded by aquatic organisms,
such as gastropods and ostracods
that precipitate shells of calcium
carbonate (CaCO3).
Scientists can measure the 18O to
16O ratio in fossil shells in sediment
cores to reconstruct changes in
evaporation/precipitation through
time, thus inferring climatic change.
Illustration © From Curtis,
et al © 2007
Hydrology: Closed Basin Lakes
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This study consisted of
taking sediment cores
from two different lakes
centrally located on the
Yucatan.
Both Lakes
Chichancanab and
Punta Laguna are
considered to be
closed-basin lakes.
The geology of
Yucatan is karst
(porous limestone),
many of the lakes are
perched above the
water table and
isolated hydrologically
by clay-basin seals.
Illustration From Curtis, et al © 2007
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Closed-basin lakes have
simple water budgets, and
typically receive water by
precipitation, slope wash,
and groundwater seepage,
while losing a majority of
their water through
evaporation.
Therefore the lake
volume, dissolved solute
concentrations and oxygen
isotopic ratios are largely
controlled by the ratio of
evaporation to
precipitation.
This characteristic makes
closed-basin lakes
climatically sensitive to the
changing conditions of
evaporation or
precipitation.
Closed Basin
Lakes
Illustration From Curtis, et al © 2007
Sedimentation Rates
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When the cores are returned to the lab, they are split
in two halves. One-half of the core is sampled and
the other half is archived for future use.
The core that was sampled from Lake Chichancanab
had a total length of 4.9 m with a basal radiocarbon
age of 9000 years BP.
The sedimentation rate averaged about 0.5 mm per
year.
The core was sampled continuously at 1-cm intervals
over its length.
A 1-cm sample in the Lake Chichancanab core
represents about 20 years of deposition.
The sedimentation rate determines the temporal
resolution of study and as a result, scientists are able
to reconstruct climatic changes that lasted for
multiple decades or longer.
The sediments of Chichancanab consisted of
alternating layers of organic matter, calcite, and
gypsum.
Punta Laguna Core
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The total core length from Punta
Laguna was 6.3m with a basal
age of 3300 years.
The sedimentation rate averaged
2 mm/year, which is about four
times greater than the
sedimentation rate in the core
from Chichancanab.
A 1-cm sample for the Punta
Laguna core represents only 5
years of deposition, permitting the
resolution of much shorter climatic
events.
Sediments in the Punta Laguna
core are composed almost
Above and previous cores are
entirely of calcium
similar representation taken
carbonate(CaCO3).
from recent Trinidad expedition.
Lake Chichancanab Core
Results
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Data from the Lake Chichancanab core supports the
following interpretation that begins at the base of the
core:
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From 9200 to 7800 years BP, there was no lake at the coring site as
indicated by the absence of aquatic microfossils and the presence of
land snails.
Beginning at about 7800 years BP, the lake began to fill but the
salinity was much higher than today.
Evidence for this includes high sulfur content indicating gypsum
precipitation, very high 18O and 16O ratios in both ostracods and
gastropods, and the occurrence of a benthic foraminifera, Ammonia
beccarri.
Foraminiferas are almost exclusively marine forms but this species
can tolerate a wide range of salinity (7 to 67 ppt); however, it only
reproduces between 13 and 40 ppt. The large number of specimens
of A. beccarri suggests salinities of at least 13 ppt (the modern lake
salinity is only 4 ppt).
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Data from Lake Chichancanab
From Curtis, et al 2007 ©
Oxygen
Isotope
Results
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This slide compares the oxygen isotope record on the same species of
gastropod between the two lake cores: Punta Laguna (above) and
Chichancanab (below).
Note that the Punta Laguna record is much higher resolution owing to
higher sedimentation rates than Chichancanab.
Within the error of the radiocarbon age models, the period of higher
mean 18O values in Punta Laguna correlates with the interval of
increasing sulfur and oxygen isotope values in Chichancanab.
From Curtis, et al © 2007
Punta
Laguna
Oxygen
Isotope
Results
The oxygen isotope data measured on ostracods from Punta Laguna
sediments have been converted from radiocarbon years to calendar
years and compared to Mayan cultural periods.
 Superimposed upon the mean changes in the record are distinct
peaks that represent arid climate conditions.
 These peaks occur at 585 A.D., 862 A.D., 986 A.D., 1051 A.D. and
1391 A.D. Error is approximately +/-50 years.
Ostracod Climate Data
From Curtis, et al © 2007
Comparison of Ostracod Data and
Maya Cultural Periods
From Curtis, et al 2007
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The first peak at 585 A.D. coincides with the early/late Classic boundary.
This boundary is associated with the "Maya Hiatus", which lasted between
530 and 630 A.D.
The Maya Hiatus was marked by a sharp decline in monument carving,
abandonment in some areas and social upheaval.
This event may have been drought-related.
Comparison of Ostracod Data
and Maya Cultural Periods
From Curtis, et al 2007
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During the next 200 years from 600 to 800 A.D., the late Classic
Maya flourished and reached their cultural and artistic apex.
The next peak in 18O/16O occurs at 862 A.D. and coincides with the
collapse of Classic Maya civilization between 800 and 900 A.D.
The earliest Postclassic Period was also relatively dry between 986
and 1051 A.D. At about 1000 A.D., mean oxygen isotope values
decrease indicating a return to more humid conditions.
Cariaco Basin
(Venezuela)
Some of the best available climate records
for the lowland Maya region
Annual laminations
Results
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Although a Postclassic
resurgence occurred in
the northern Yucatan,
city-states in the
southern lowlands
remained sparsely
occupied.
These findings
support a rather strong
correlation between
times of drought and
major cultural
discontinuities in
Classic Maya
civilization.
Tikal Temple I and Temple II
Climate Change
and Classic Maya
Collapse
Cariaco Basin
laminated sediments
Mayan collapse
occurred during a
150-year drought!
wet
Haug G H, Gunther D, Peterson L C
D, et al. 2003. Climate and the
collapse of Mayan civilization.
Science, 299: 1731- 1735
dry
0
1
2
What can be learned from these examples?
Complex societies are sensitive to climate change.
Paleoclimate records document changes in climate
which surpassed modern variability.
Other social factors in each case may have contributed
to observed collapse.
Collapse occurred despite evidence that these cultures
had large buffering capacities.
Conclusions
Modern and ancient cultures:
- Thrive in marginal environments.
- Plan for the future based on recent past (regrettably)
- Learn and adapt (fortunately).
Only ancient cultures experienced century-scale
drought.
Their past can be a guide to our future.
Lessons from the past
Complex societies are both adaptive and
vulnerable to climate change.
Past climate changes far surpassed modern
variability.
Collapse occurred despite large buffering
capacities.
• Effects of Deteriorated Environment Event
on the Neolithic Culture of China, around 5
000 a BP
• A number of environmental records reveal that there was a rapid
environmental deterioating event all over the world ca 5000 a BP
• During this period, there was a movement of vegetations zone to south
in the southern China
• lower sea level along the coast in the southern and eastern China, and
desertificat ion in some sites of northern China
•
there was a fargoing regradation or discontinuity of Neolithic culture in
China
• there were also many records of the state of culture development
consistent with the environmental changes all over the world.
A. 敦德冰芯氧同位素
B. 岱海湖面变化
C. 螺髻山温度变化
D. 青海湖温度变化
E. 藏东南年均温变化
F. 大地湾孢粉浓度变
化
G. 博斯腾湖碳同位素
变化
H. 长白山地区温度变
化
I. 华南地区海平面变
化
J. 察素齐孢粉浓度变
化
K. GRIP 冰芯
甲烷浓度变化
L . 长江中下游地区温
度变化
M. 洱海碳同位素变化
前仰韶文化期( 8. 3~ 6. 9 ka B. P. )
6. 9 ka B. P. 前后出现一次寒
冷气候,终止了前仰韶文化
仰韶文化期( 6. 9~ 5. 0 ka B. P. )
5. 0 ka B. P. 前后的一次寒冷气
候，终止了仰韶文化期
龙山文化期( 5. 0~ 4. 0 ka B. P. )
4 ka B. P. 前后，结束了大暖期
气候, 也结束了新石器文化, 中国
历史进入文明史阶段
环境变化影响史前文化的原因
• 气候变化导致生态系统的变化
• 生态系统的变化导致植被的变化
• 植被的变化又导致影响人类生存的生物营养源
的变化
• 进而导致人类文化的变化