week 11 summary

Question 1

What has played a key role in human evolution

and migration?

Answer 1

climate

Question 2

What is the Savannah hypothesis?

Answer 2

drying trend in Africa
Tropical rainforest transitioned to grassland savannah
human Ancestors forced onto the ground,
encouraging bipedalism, rapid movement and resourcefulness

Question 3

What is the Variable selection hypothesis?

Answer 3

Rapid climate changes , favouring those who had traits that were useful to surviving in an increasingly challenging environment
Humans as ‘master invaders’

Question 4

What is the Pulsed climate hypothesis

Answer 4

Hominin expansion and diversification associated with
orbitally driven climate pulses
Stepwise expansion in brain size 1.9 Ma coeval with
occurrence of ephemeral lakes in the Rift valley

Question 5

What might have facilitated the development of agriculture?

Answer 5

the more stable Holocene environment

Question 6

What has climate change likely contributed to in the past?

Answer 6

Climate change has likely contributed to the

collapse of civilisations in the past

Question 7

What is the Early Anthropogenic Hypothesis?

Answer 7

Humans actions have significantly impacted the climate and environment long before the industrial revolution

Question 8

What trends are different in the holocene when compared to other interglacials?

Answer 8

CH4 and CO2 are anomalous

Question 9

What caused the rise in CH4 ~5,000 years ago?

Answer 9

rice irrigation and tending

livestock

Question 10

What caused the rise in CO2 ~7,000 years ago?

Answer 10

deforestation and burning

Question 11

When do humans begin to be active contributors to the climate system?

Answer 11

10,000 to 8,000 years ago

Question 12

What had happened by 3000 years ago?

Answer 12

Hunter gatherers, farmers and pastoralists had transformed the planet

Question 13

What is the key driver over human systems?

Answer 13

Climate variability over interannual to decadal time

scales

Question 14

What are the key drivers of year to year climate variability?

Answer 14

ENSO, IOD and SAM

Question 15

When have ENSO, IOD and SAM changesed?

Answer 15

over the last 50 years

Question 16

What paleoclimate archives are used to measure decadal variability?

Answer 16

High resolution palaeoclimate records, such as tree rings, speleothems, corals and lake records

Question 17

How often does ENSo occur?

Answer 17

every 3- 8 years

Question 18

What does ENSO control

Answer 18

driver of rainfall and temperature variability particularly over eastern Australia

Question 19

What is indies is ENSO measured through?

Answer 19

• sea surface temperature

- sea surface pressure between Tahiti and Darwin

Question 20

What are the key theories relating to human evolution and climate change?

Answer 20

• Savannah hypothesis
• Variable response hypothesis
• Pulsed climate variability hypothesis

Question 21

When is the greatest increase in brain size linked to?

Answer 21

Variable selection hypothesis

period to greatest climate variability

Question 22

How may the younger dryas have enabled expansion in agriculture?

Answer 22

• Intensification of dry conditions in Eastern Mediterranean
• People gathered near dependable water sources
• Wild grains accidently germinated nearby
• So began cultivation of crops

Question 23

What are examples of human civilisations being negatively affected by climate?

Answer 23

Egyptian dynasties-Weakening of monsoon 5,000-
6,000 yr ago
Akkadian (Syria)-Abrupt abandonment of villages with increased aridity ~4,200 yr ago
Maya civilisation- collapse of lowland Maya civilisation ~800 – 1000CE
• Evidence of a 20- 60% reduction in rainfall

Question 24

When did CO2 diverge in mid holocene?

Answer 24

~7,000 years ago
• released due to deforestation,
burning

Question 25

When did • CH4 diverge in mid holocene?

Answer 25

~5,000 years ago

• release due to irrigating fields, burning biomass, livestock tending, organic waste

Question 26

What are the counter arguments to Early Anthropogenic Hypothesis?

Answer 26

• Humans were too few in number
• Early human greenhouse gas emissions had only a
small impact on climate
• Increase in greenhouse gases due to natural climate
processes

Question 27

How have ENSO, IOD and SAM changesed?

Answer 27

all three have intensified in recent years

Question 28

What does a La NIna mean?

Answer 28

stronger trade winds
bigger east to west difference
greater rains in aus
cooler temp in aus

Question 29

What does a El Nino mean?

Answer 29

trade winds weaken or reverse
warm waters drift back east
In Aus- less rain, warmer temp

Question 30

Can you get El Nino events for two years back to back?

Answer 30

yes

Question 31

What does a positive IOD mean?

Answer 31

weakened westerly winds
cooler waters in aus
less rain

Question 32

What does a negative IOD mean?

Answer 32

westerly winds strengthen
warmer winds in aus
rain in aus

Question 33

What is the IOD time cycle?

Answer 33

3-5years

Question 34

What does a neutral IOD mean?

Answer 34

normal temp

little influence

Question 35

What does a positive SAM mean?

Answer 35

shift south in winds
drier winter conditions south australia
more rain northern east coast(winter)
in summer-more rain on east coast

Question 36

What does a negative SAM mean?

Answer 36

winds more north
in winter more rain and snowfall in south less in east
in summer below average rainfall- increase chance of heat wave

Question 37

What is sam?

Answer 37

unusual shift northward/southward of roaring 40s and 50s

lasts around 2 weeks