Paleoclimate change

Question 1

What can we learn from past climates?

Answer 1

• context for current observations
• natural variability
• ‘baseline’ reference for man-made climate change
• test predictive models

Question 2

Which past epoch is the best analogue for our current situation?

Answer 2

Pliocene

Question 3

What were CO2 concentrations during the Mid-Pliocene?

Answer 3

Estimated between 360-400ppm

Question 4

When was the Mid-Pliocene?

Answer 4

3.3 to 3 Ma years ago

Question 5

What were sea levels like during the Mid-Pliocene?

Answer 5

25-30m higher

Question 6

What were higher latitude air temperature likes during the Mid-Pliocene?

Answer 6

10-20ºC higher

Question 7

What is the speed like when transitioning into a glacial period? and interglacial period?

Answer 7

Slow descent into glacial periods but rapid descent into interglacials (shown in the Vostok ice core)

Question 8

How does sea level change at glacial maximums?

Answer 8

130m below current levels

Question 9

What are general conditions like in glacial periods?

Answer 9

Colder, dustier and generally drier than interglacial periods

Question 10

What is Milanković theory?

Answer 10

Theory that orbital changes cause interglacial and glacial periods

Question 11

When was Milanković theory first proposed?

Answer 11

1920

Question 12

What is eccentricity?

Answer 12

Changes in the earths orbit around the sun from circular to elliptical

Question 13

How often does eccentricity vary?

Answer 13

Varies on a time scale of 96k years

Question 14

How much does eccentricity vary by?

Answer 14

0-0.07 (i.e. the orbit is can be stretched 7% away from a circle)

Question 15

How does eccentricity vary radiation?

Answer 15

Same incoming solar radiation is the same but can alter intensity between the two hemispheres

Question 16

What impact does an eccentricity have on radiation intensity over the globe?

Answer 16

28% difference between the hemispheres

Question 17

What is our current eccentricity?

Answer 17

0.0174 … the southern hemisphere receives 6.7% more radiation a year

Question 18

What is obliquity?

Answer 18

Tilt .. variations in this can occur

Question 19

What is current obliquity?

Answer 19

23.5º

Question 20

How does obliquity vary?

Answer 20

Varies between 21.5º and 24.5º with a period of 41k years

Question 21

What happens during large obliquity?

Answer 21

Seasons become more exaggerated

Question 22

What is precession?

Answer 22

The wobble of the axis that can change the difference between seasons

Question 23

What is the earths period of precession?

Answer 23

19-21 k years

Question 24

What was deglaciation triggered by in the last glacial period?

Answer 24

Rise in insulation in the northern hemisphere causing a change in radiative budget

Question 25

What is the Bølling-Warming event?

Answer 25

An abrupt warm and moist interstadial period that occurred at the end of the last glacial period. We don’t know what caused this.

Question 26

What was the temperature rise during the Bølling-Warming event?

Answer 26

4-5ºC in a few decades

Question 27

What was the Younger Dryas event?

Answer 27

A cooling period for around 1ka due to a change in meltwater route which created a fresh water input, affecting density structures and ocean circulation, weakening a warm current that brought warm water from the tropics to the mid latitudes

Question 28

How did temperatures in the late and early Holocene compare?

Answer 28

Early Holocene was warmer than the late Holocene (not what we would expect from model predictions)

Question 29

What is the Holocene?

Answer 29

Time of earth history (epoch) since the last glacial. The last 12,000 years and the current interglacial period.

Question 30

What factor had a major effect on climate over the last 500 Ma that isn’t relevant to present day climate change?

Answer 30

Continental drift

Question 31

Since the end of the Cretaceous, what was the maximum CO2 concentration experienced?

Answer 31

2000-2500ppm (over five times higher than current conditions)

Question 32

On what time scaled does obliquity change?

Answer 32

41k years