Lec 18: Case Study – Holocene climate change

Question 1

What causes glaciations?

Answer 1

Milankovitch cycles (eccentricity, tilt, precession)

Question 2

On which scale is holocene climate change studied?

Answer 2

the local scale (not global)

Question 3

What happened during the Younger Dryas?

Answer 3

Abrupt cooling phase.

Polar front shifted in less than 10 yrs

Question 4

Why did the north pole heat up during the Younger Dryas?

Answer 4

thermohaline circulation was halted by glacier melting.

hot water stayed in north

Question 5

What happened during the African Humid Period?

Answer 5

abrupt transition to wet phase

Question 6

What percentage of the Earth is untouched by humans?

Answer 6

30%

Question 7

How does solar radiation affect methane concentration in atmosphere?

Answer 7

more solar radiation = more methane (more active wetlands and melting of permafrost)

Question 8

Ruddiman’s Early Anthropogenic
Greenhouse Hypothesis (2003)?

Answer 8

CO2 and methane levels actually started going up when humans started agriculture (5000 years ago)

Question 9

Why did the onset of agriculture increase carbon and methane in atmosphere?

Answer 9

cutting and burning of trees, livestock, wetlands

Question 10

Where would we be without agriculture?

Answer 10

strong evidence that we would have been in a glaciation