Cliamte Of Distant Past (14)

Question 1

What is a trend?

Answer 1

Global temperatures change over a set period of time. Generally over long geological time periods.

Question 2

What are rhythms?

Answer 2

Repeating cycles of climate. Generally shorter on a geological time scale.

Question 3

What defines earth’s climate? What are the current and past trends?

Answer 3

Earth’s climate is defined by global temperature averages - not weather patterns.

Climate varies between hot and cold global averages.

Recent history: rapidly repeating rhythms of mild temperature changes.
Ancient climate: extended trends and greater temperature extremes.

Question 4

What is an ice age?

Answer 4

Persistent glaciers are present.

Question 5

What is a glacial period?

Answer 5

Glaciers are growing.

Extreme cold can lead to global glaciation: snowball earth

Question 6

What is an interglacial period.

Answer 6

Glaciers are receiving.

Question 7

What is a hot house earth?

Answer 7

No persistent glaciers present.

Question 8

How does earth’s climate move between the different types of climate extremes?

Answer 8

1. Climate forcing
2. Feedbacks
3. Tipping points

Question 9

What are climate forcings?

Answer 9

Factors which have been shown to influence global climate.

Question 10

What is a tipping point?

Answer 10

The physical or ecological state of an area (or the planet) crosses an “irreversible” threshold of climate forcings.

Irreversible on a human time scale.

On a geological time scale, all climatic changes have been shown to be reversible.

Question 11

What are the processes that drive change in solar radiation?

Answer 11

1. Availability of hydrogen fuel.
2. Rate of burning for hydrogen fuel.

Question 12

How does the sun make its energy?

Answer 12

Hydrogen atoms in the sun are forced together through intense pressure from gravity.
- fuse into helium
- releases energy

Helium is heavier than hydrogen
- increases pressure at the core
- increased pressure increased rate of hydrogen fusion

Question 13

Is an increase in solar radiation a factor in the warming of the earth?

Answer 13

Not a factor for modern rapid temperature increases.

A major factor influencing global climate in the past.
- there was considerably less energy reaching the surface of the earth
- less energy avail bel to heat the planet

The sun was only producing 80% of the luminosity it does today. The high CO2 in the atmosphere helped keep the planet warm.

Question 14

What are notable features of early atmosphere?

Answer 14

• lack of O2 (and O3)
• high levels of CH4
• high levels of CO2

first life involved many methanogens, which gave birth to the carbon cycle

Question 15

Explain the early stages of photosynthesis.

Answer 15

The evolution of photosynthesis decreased atmospheric CO2 and increased atmospheric O2.

The first photosynthesizers were bacteria (not plants). Cyanobacteria produce lots of O2 waste, which changed the composition of the atmosphere.

Question 16

How did the appearance of O2 impact CH4? What were the climate effects?

Answer 16

Methanogens can only live in oxygen-free environments. Methane reacts with oxygen, and converts it to CO2.

O2 started to replace CH4 and CO2. Oxygen is not an effective GHG like CH4 and CO2 + solar luminosity was lower = Huronian Glaciation that lasted 300 MY.

Question 17

Explain the Huronian Glaciations.

Answer 17

Lasted 300 MY.

Cycles of glacials and inter-glacial periods. Possible snowball earth.

Ice-albedo feedback: positive feedback between ice formation and increasing albedo lowering temperatures.

Question 18

Explain continental drift and its effects.

Answer 18

Tectonic plates move over geological time - driven by geological processes producing new crust and recycling old crust.

The location of landmasses on the on the surface planet influences temperatures.
- influences ocean currents, solar radiation budget, precipitation.

Question 19

Explain how continental drift affects ocean currents.

Answer 19

Global ocean currents transport heat energy from warmer equatorial region (energy surplus) to colder attitudes. Helps to raise temperatures in colder latitudes.

The movement of continents can isolate or redirect oceanic currents.
- chasing direction of heat transfer.
- eliminate heat transfer in a region.

Question 20

Explain how continental drift affects solar radiation.

Answer 20

The angle of insolation differs across the planet, so the energy budget is unevenly distributed globally.

Albedo of the Earth’s surface is not equal - land reflects more thermal energy than the ocean.

When we change the albedo of the equator, it gets colder. Greater reflection of thermal energy from within the critical zone of energy surplus, so less energy is available to transfer to areas or energy deficit. Less energy is being spread around globally.

Question 21

Explain how continental drift affects precipitation.

Answer 21

Equatorial regions generally have greater rainfall than other latitudes.

Rainfall contributes to the carbon cycle through chemical weathering.
- CO2 and H2O form carbonic acid in the atmosphere
- rainfall containing carbonic acid weathers exposed rocks
- releases HCO3-, Ca2+, and others

Fewer minerals from rocks left to be removed by carbonic acid overtime. Older rocks are being exposed to chemical weathering.

Plate tectonics can produce new rocks: mountain-building events and volcanic events.
- These new rocks have a greater amount of carbonate, calcium, and other minerals to weather in a short period of time.

Previously buried rocks now exposed to chemical weathering from rainfall.

Location of the mountain is important: more rainfall = more chemical weathering
- greater impact on global climates if it occurs in equatorial regions

Question 22

What are the different types of movement changes of the earth?

Answer 22

1. Eccentricity.
2. Obliquity (tilt angle).
3. Precession (tilt direction).

Question 23

What is eccentricity? What does it influence.

Answer 23

Changing distance between the sun and the Earth, as the Earth orbits the sun.

The Earth’s orbit is not a circle, but an oval.

The orbit path influences:
- length of seasons (more eccentricity = more difference)
- solar radiation of earth

Question 24

What is obliquity and what does in impact?

Answer 24

Earth’s rotation on an angle.

Earth’s tilt creates differences in solar insolation seasonally.
- produces seasons.

A greater tilt = greater extreme between seasons.
- hotter summers and cooler winters.

Question 25

What is precession and what does it impact?

Answer 25

Direction of the earth’s tilt. Points in one direction or the opposite and flips every 23 000 years.

Explains why seasonal extremes are milder in the Northern hemisphere, but more extreme during summer in the Southern Hemisphere.

Question 26

What are the changes in earth’s movement called? Explain what it entails.

Answer 26

Milankovic cycles. During these cycles, there are changes in the amount and location of solar radiation on the planet.

Period of very high insolation in interglacial periods. Glacial periods often preceded by a period of excessively low insolation.

Question 27

Can the Milankovic cycles change temperatures?

Answer 27

Changes in insolation can cause changes in temperature BUT feedbacks are needed to amplify small changes in temperature into climate change.

Question 28

What is proxy data? Give examples.

Answer 28

Data derived from sources that are not direct measurements of the variable of interest, but can be used to infer the measurements of the variable of interest.

Long time scale: geological records
Short time scale: ice cores

Question 29

What are examples of geological data in terms of past glaciations?

Answer 29

1. Glaciers carve out characteristic valleys in landscapes as they form. Deposits left at the melting ends of a glacier are characteristic.
2. Knowledge of plate tectonic movement can be used to infer glacier extent over geological time.
3. Ice cores: atmospheric gases trapped in air pockets at the time of glacier formation.
   - O16/O18 ratios to determine past global temperatures