History of Climate Change

Question 1

What are the importance’s of understanding geological history?

Answer 1

• Establishing a link between CO2 and temperature
• Provides context for current climate crisis
• Allows sensitivity of climate models to be studied
• Demonstrates the central role of life in the earth system
• Shows how earths environment was different in the past
• Suggests how life adapts to the environment

Question 2

How is the link between CO2 and temperature established?

Answer 2

Palaeo-temperature proxies: biological (tree rings, fossils) and geochemical (oxygen isotope ratios)
Palaeo-CO2 proxies: biological (phytoplankton, liverworts) and geochemical (boron proxies)

Question 3

How does knowledge of geological history provide context for the current climate crisis?

Answer 3

Can compare with past climatic events, such as the Paleocene-Eocene thermal maximum (PETM)

Question 4

What was the Palaeo-Eocene Thermal Maximum (PETM)?

Answer 4

Happened 56 million years ago
Doubled atmospheric CO2.
Causes warming of 5.C
Decreased phytoplankton abundance

Question 5

How can equilibrium climate sensitivity be inferred?

Answer 5

Using past climates, comparing the temperature between the last glacial maximum and the Holocene using isotope proxies.
Can show expected sea level rise: complete loss of Greenland and West Antarctic ice sheets.

Question 6

How is life a central role of the earth system?

Answer 6

It plays roles in oxygen and carbon cycles.
Photosynthesis has oxygenated the atmosphere.

Question 7

What was the ‘Green Sahara’?

Answer 7

Events during the Holocene and Pleistocene, humid conditions.
Formed lakes, grasslands, forests.

Question 8

What was ‘Hot house earth’?

Answer 8

Ice free Antarctica during Mesozoic.

Question 9

What are ‘Snowball Events’?

Answer 9

When the earth is frozen solid, covered in ice.

Question 10

What was earths Archaean atmosphere?

Answer 10

• No O2
• 10 times less CO2 than now
• High methane concentrations
• Weak sun
• Greenhouse effect prevented the earth from freezing

Question 11

What happened when photosynthesis first occurred?

Answer 11

First photosynthetic organisms were prokaryotic cyanobacteria.
Oxygenated the atmosphere, oxygen destroyed earths methane greenhouse effect
Led to an ice-albedo-temperature feedback loop. Earth freezed.

Question 12

What are some past snowball events?

Answer 12

• Huronian: oxygenation of earth caused drop in methane
• Sturtian: drop in CO2 due to increased sequestration in the ocean

Question 13

How have each snowball event thawed?

Answer 13

Volcanic CO2 production strengthens the greenhouse effects and thaws the earth.