Transcript Climate change

Rob Wilson
Thanks to Andy Dugmore, Richard Tipping and Dave Stahle for input/advice
Environmental Change
 A varying balance between:
 Anthropogenic Influences
 Climatic Influences


Temperature
Precipitation
Environmental Change and Society
 A two-way process of
 Environmental change influences Society
 Societal change influences the environment
 Teasing out and identify between these two directional
processes may not always be straightforward
Cultural change - Theories
 “Cultural Determinism”
 Culture alone determines culture.
 “Environmental determinism”
 Human culture is determined by the environment.
 “Possiblism”
 Compromise: The natural environment influences the
range of available (possible) human choices.
Climate - Society
Human populations adapt to the climate:
• We minimize the downside
• We maximise the opportunities
• It shapes our:
• Agriculture
• Economy
• Culture
We are accustomed
to the
“mean climate”
• Way of life
But …
We are
sensitive to
“climate
variability”
Human population is also stressed by the climate :
• Weather extremes:
• Drought & Flood
• Heat & cold waves
• Storms
• Climate change:
• Natural variability
• Human induced changes
Future climate change……
IPCC 2007
So….
 can we learn about our future by studying the past?
 We always say we can, but there are likely no climatic
analogues over the past 8000 years equivalent to the
next 50 years?
 Also – the current geopolitical situation is radically
different than any period in the past
Jared Diamond (2005)
Collapse: How Societies Choose to Fail or Succeed
Defined a five-point framework of factors that may contribute to
environmental related societal “collapse”
1.
Anthropogenic environmental damage
For example deforestation contributing to severe environmental
damage
2.
Climate change
Disappearance of the Norse from Greenland and the Anasazi from the
American Southwest
3.
Hostile neighbours
Societies may be able to hold off neighbouring societies as long as
they are strong, but succumb when they weaken due to either 1 or 2
4.
Decreased support by friendly neighbours
If one society collapses, it may no longer supply things which are
essential for nearby societies – the collapse of the friendly society may
be due to 1 or 2
Diamond’s Fifth Point
 A societies response to problems is critical, and will
determine whether or not the society survives
 So for us today – the threats are:




Global climate change
War/conflict
Energy availability
Economic dislocation…..etc
 nearly all are related to human choice rather than
natural causes
Lawler 2010
Collapse vs. Change
 In reality, cultures do no necessarily “collapse”
 Total collapse is very rare
 Rather cultures change and adjust
 Migration
 Change in resource utilisation
 Political change
 Life style change
Climate - environment – Society
lessons from the past
 How have cultures responded to short/longer term
climate/environmental changes?
 NB. It is crucial to combine detailed and well-dated
palaeoclimate and historical/archaeological records.
 As we go back through Holocene – quality of records degrade
 To some Case Studies……..
 Can be thought of as “completed experiments” through
which causal factors can be examined
Tree-ring record of US drought
MEGA DROUGHTS
Cook et al. (2004)
The Dust Bowl Drought
Instrumental PDSI
Tree-Ring Reconstructed PDSI
Coast-to-coast
dryness
Worst drought in 350
years
1931-1940
Impact & drought
itself aggravated by
poor land use
practices?
1931-1940
largest
environmental
migration in US
history
Dalhart, Texas, 1938
Stahle pers comm
The 16th Century Megadrought
The most severe-sustained North American drought of the past 500 years?
50-years of incipient to severe drought in Mexico, 1540-1589
1560-1589
Worst 30-years = 1560-1589
Demographic catastrophe
Cocoliztli: hemorrhagic fever
Stahle pers comm
Sequence of climatic extremes, 4 largest epidemics.
Disease agent unknown, leading hypothesis: rodent
reservoir amplified by climate & ecological extremes.
Lost Colony & Jamestown Droughts
Stahle, D. et al. 1998. The Lost Colony and Jamestown Droughts. Science 280(5363): 564-567.
Great Pueblo Drought
Square Tower House
“Great Drought” 1272-1298 AD (~26 years)
Mesa Verde, Colorado
1276-1297
No
Data
• Late 13th Century drought and apparent de-population of large areas of
Colorado Plateau.
• Cause of Anasazi abandonment still debated
• drought, over-exploitation, warfare, religion
• we will never truly know,
Cook et al. (2004), Benson et al. (2006)
The Norse Greenland settlement
Records of diet through time show adaptation to changing climate
A potential ‘resilience trap’?
The marine-focussed adaptation was
effective over century time scales but
With resultant loss in resilience?
Double exposure? Plague may have reached
Greenland in 15th century; it certainly caused the
collapse of the Norwegian economy ( & market
for Greenland ivory)
As cumulative
temperatures
decline, marine
component of
Norse diet
increases (up to
80%)
Triple
exposure?
Inuit
contacts:
source of
conflict, or
source of
trade goods
(furs)?
Dugmore pers comm; Dugmore et al. 2007
THE TRANSITION TO AGRICULTURE IN THE BRITISH ISLES
THE TRANSITION TO AGRICULTURE IN THE BRITISH ISLES
 Major cultural change - 6000 cal BP
 Long-standing debate over how this occurred:
 the early Neolithic ‘package’ (farming, pottery,
monumental architecture) was somehow absorbed by
Mesolithic hunter-gatherers

described as a ‘process’ to blur the need for causal factors and
emphasise cultural determinism
 rapid change made by incoming continental farmers
Tipping pers comm
THE TRANSITION TO AGRICULTURE IN THE BRITISH ISLES
 Bayesian dating now shows an abrupt beginning at
c. 6000 cal BP
 Suggests an ‘event’ rather than a process
 begs the questions
 why the invasion?
 why then?
Tipping pers comm
Answers??
 Population pressure on continent?
 no evidence for this
 Climate downturn c. 6400 to 5800 cal BP
 but what was the mechanism?
 Climatic downturn resulting in failure of wild resources for
hunter-gatherers – increasing unpredictability
 Concurrent decline in tree populations (Elm, pine etc)
 Climatic downturn also affects continental farmers

Migration some west to the British Isles
 Agriculture - more reliable food resource – abandonment
of hunting-gathering
Tipping pers comm
THE TRANSITION TO AGRICULTURE IN THE BRITISH ISLES
 What is needed – ongoing research
 Better resolved reconstructions of


Past climate
Vegetation change – including wild resources
 Putting archaeological record on the same time-line to
examine


Cultural/societal changes
Diets of hunter-gatherers vs. later Neolithic cultures
Leverhulme Trust Project - RELIC:
Reconstructing 8000 years of Environmental and
Landscape change in the Cairngorms
 Pine Macrofossils
 Long TR chronology
 Palynology
 Limnology
Geochemical analysis
 Comparison to regional
archaeological record
Wilson and Edwards (2010-2012)
Summary - Environmental/Societal Change
 Societies rarely collapse
 They do however change
 Dependent on their overall resilience
 A key point is to understand the circumstances when
environment change may have an effect
 this is highly conditional on the social-political-
economic context
 Small changes may have significant effects on a
sensitised system, whereas in other contexts dramatic
changes may have comparatively limited effects
Finally…………………..
 Moments of Crisis:
From Coincidence to Hypothesis in Scottish Prehistory
 One-day ‘round table’ Workshop: Saturday January 22nd 2011
 Sponsored by Scottish Alliance for Geoscience, Environment &
Society (SAGES) / Scottish Archaeological Research Framework
(ScARF) Collaboration
 Organised: Richard Tipping (Stirling University), Bob McCulloch
(Stirling University), Jeff Sanders (ScARF) and Rob Wilson (St.
Andrews University).