Lecture 21: Present Interglacial (Holocene)

Question 1

What MIS was the last interglacial?

Answer 1

5/5e

Question 2

What are 5 reasons to study the Holocene?

Answer 2

1. We are in it
2. Previously thought to be relatively stable period, but actually is not
3. Anthropogenic changes
4. Range of potential forcings
5. Wealth of evidence

Question 3

What are 5 anthropogenic changes that occur within the Holocene?

Answer 3

1. human-climate interactions
2. modern civilisation emerges
3. Dawn of agriculture
4. Explosion of art, technology, and culture
5. Population rise

Question 4

What are the range of potential forcing mechanisms for changes in the Holocene?

Answer 4

Milankovitch, sub-milankovitch, solar hotspot activity, volcanic activity, greenhouse gases (natural and anthropogenic), comet impacts

Question 5

Why is there so much evidence for the Holocene period?

Answer 5

There has been less time for the records to have been exposed to things that would have caused their decomposition or disappearance

Question 6

How do we know that the evidence that exists for the quaternary are good estimates?

Answer 6

because there is continuity between them and the more recent instrumental records

Question 7

What were the two studies carried out that correlated with each other to produce a rough estimation of how climate has transformed over the Holocene?

Answer 7

Blytt and Serander - studied peat decomposition

Post and Godwin - studied changing pollen types found within lake peat records

Question 8

What were the three periods that defined the changes in climate of the Holocene in chronological order?

Answer 8

Rapid Warming, thermal maximum, cooling

Question 9

What happened to insolation during the LGIT across the northern hemisphere? and how did it change to define the three periods of climate during the Holocene?

Answer 9

There was an increase of it during summer but then a decrease during winter. Over the Holocene period the difference between the two seasons diminished meaning that there was increasingly less summer insolation as well as increasingly more winter insolation as you got closer to the present day

Question 10

What did Davis and Brewer (2003) contribute to the record of climate changes over the Holocene?

Answer 10

They reconstructed temperature using changing pollen assemblages in the record over the Holocene like had been done previously using the other proxy methods. Their conclusion was similar to the earlier work and confirmed that there were three notable stages throughout the quaternary but that it was actually more complex

Question 11

What sort of complexity was there in the changes of climate over the Holocene? What was this demonstrated by?

Answer 11

Regional variation across latitude - demonstrated by greater seasonality in North-western Europe compared to Central Europe

Question 12

What was there also evidence of in the study carried out by Davis and Brewer (2003)? but what was a problem?

Answer 12

Short term variability - but we needed a broader spatial understanding

Question 13

What did Wanner et al. (2008) contribute to the estimations of climate across the Holocene period?

Answer 13

He plotted all the evidence for global changes on a map to identify the global changes and how they would interact to produce changes in weather

Question 14

What did the global scale nature of the changes illustrate?

Answer 14

The presence of global teleconnection across the world.

Question 15

What was the glacier bipolar seesaw conclusion of Wanner et al.’s (2008) work?

Answer 15

In the northern hemisphere there was evidence of glacial re-advance whereas in the South (demonstrated by South America record) there was a decline

Question 16

What suggested that there was some sort of periodicity or cycle enforcing the bipolar glacial changes observed by Wanner et al. (2008)?

Answer 16

The timings of the advance and retreat in the opposing hemispheres was consistent

Question 17

What are bond events?

Answer 17

Similar to Dansgaard-Oeschger events in that they occur in the same intervals, but instead bonds events are characterised by increased cooling periods during the Holocene

Question 18

What is the estimated periodicity of the Bond events but what does it illustrate?

Answer 18

1470 years + or - 500 years. The high standard deviation demonstrated the large degree of uncertainty

Question 19

What was the 4.2kyr event?

Answer 19

A pronounced dry event across mid to lower latitudes

Question 20

What is the 4.2kyr event thought to have caused?

Answer 20

Social disruption and the collapse of civilizations

Question 21

What was the 4.2kyr event characterised by in Northern Africa? What was this inferred from?

Answer 21

Increase in the amount of dust in the area as there was less water. Inferred from marine record off the western coast of Africa

Question 22

What did the 4.2kyr event coincide with?

Answer 22

Bond Event 3 identified from Ice Rated Debris

Question 23

What did Roland (2012) do for his phD?

Answer 23

He collected 117 records across the world that contained evidence of the 4.2kyr event and from that estimated what the associated climatic impacts might have been.

Question 24

What conclusion did Roland (2012) reach from his phD?

Answer 24

Evidence of global teleconnections that produced relative drying of the climate in the tropics and sub-tropics as well as relative cooling in the northern hemisphere while the southern hemisphere displayed relative warming

Question 25

What was missing form Roland’s phD paper which nobody else could identify either?

Answer 25

There was no explanation of mechanism that could cause the climate changes

Question 26

What were the proposed causes of the changes that took place in the 4.2 event that were identified by Roland? What was the result?

Answer 26

Solar activity, artefact of arithmetic averaging, glacial meltwater, volcanic activity. There was even debate whether the changes were real or imaginary. The result was that it was a combination of multiple factors

Question 27

What has temperature in the Holocene demonstrated over the past 1000 years?

Answer 27

An unprecedented rise over the past 1,000, 2,000, 800,000 and possibly even 10 million years.

Question 28

What is research focused on at the moment in terms of the changes that are taking place in the past 1000 years?

Answer 28

Whether it is natural variability or anthropogenically induced.

Question 29

When did the Medieval Warm Period happen?

Answer 29

between 1000 and 1200 AD

Question 30

What was supposedly possible in Scotland during the medieval warm period?

Answer 30

To grow grapes for wine

Question 31

When did the Little Ice Age happen?

Answer 31

1600-1900AD

Question 32

What happened during the little ice age?

Answer 32

Frost Fairs - fairs on the river Thames

Question 33

What do recent temperature compilations suggest about the Medieval Warm Period and Little Ice Age?

Answer 33

that it could well have occurred

Question 34

What debate is there around when humans started to influence climate?

Answer 34

When did GHGs, land cover (albedo) and aerosols etc. emerge as an influence and which plays the most important role?