lec 12: Climates Distant Past

Question 1

what is characteristic to ancient climates?

Answer 1

extreme long periods at one of the 2 temperature extremes

Question 2

what is an ice age?

Answer 2

a period of time where at least some region of the globe is cold enough to form persistent glaciers, so big regions of ice that last more than a season.

Question 3

what are the 2 states of an ice age?

Answer 3

glacial period: glaciers are growing

interglacial period: glaciers are receding

Question 4

what is a snowball earth?

Answer 4

a period of extreme glaciation where the entire surface of the earth is covered in glaciers

Question 5

what is a hot house earth?

Answer 5

no glaciers present

Question 6

how does a planet make a switch from these extreme temperatures?

Answer 6

3 concepts:
1.climate forcing
2. feedbacks
3. tipping points

Question 7

what are trends?

Answer 7

global temperature change over a set period of time, generally over long geological time periods

Question 8

what are rhythms?

Answer 8

repeating cycles of climate, generally shorter on a geological time scale

Question 9

what is a climate forcing?

Answer 9

factors which have shown to influence global or regional climate

Question 10

what are feedbacks?

Answer 10

A process which can amplify or dampen a climate forcing (positive vs negative)

Question 11

What is a tipping point?

Answer 11

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

Irreversible on a human scale
on a geological time scale, all climatic changes on earth to date have been shown to be reversible

Question 12

what changes in the life span of the sun

Answer 12

how much energy it can output, depends on how much hydrogen fuel there is (fusion)

Question 13

how is energy formed (in the sun)

Answer 13

Hydrogen atoms are forced tgt through intense pressure from gravity (fuse into helium + releases energy)

Helium is heavier than hydrogen = increases pressure at the core = increases rate of hydrogen fusion! [feedback]

Question 14

has an increase in solar radiation increased global temperature?

Answer 14

it has but not in a significative way

Question 15

how did solar radiation have a major role in changing temperatures in the global climate distant past?

Answer 15

there was considerably less energy reaching the surface of the earth (less energy to heat the planet)

Question 16

How could less energy maintain the same average warm temperatures we see globally today?

Answer 16

A change in atmosphere composition! It used to have a much higher carbon concentration (10%) (it’s now around 0,04%)

Question 17

how was the first atmosphere likely formed?

Answer 17

gases released from cooling planetary rocks kept close due to gravity

Question 18

what are the later atmospheric influences?

Answer 18

Life and Oxidation

Question 19

what are the notable features of early atmosphere (3)

Answer 19

1. Lack of O2 (and O3)
2. High level of CH4
3. High level of CO2

Question 20

how did methane appear?

Answer 20

thanks to methanogens! birth of the organic carbon cycle !

Question 21

Why does CO2 decrease gradually?

Answer 21

because of the evolution of photosynthesis!
the first ones were bacterias

Question 22

why did methane decline later on?

Answer 22

the methanogens cannot survive when there is O2, it reacts with O2 and creates CO2

Question 23

what happens to global temperatures when O2 replaces CH4 and CO2 ?

Answer 23

appears a series of cycles between extreme temperatures (ice ages, glaciation and interglacial periods)

Question 24

what is the ice-albedo feedback?

Answer 24

positive feedback between ice formation and increasing albedo lowering temperatures

Question 25

what are some ways in which the planet is a technonically active planet?

Answer 25

- continental drift - redirection of ocean currents - new landmasses formed - carbon is cycled

Question 26

link plate tectonics and continental drift + the impact

Answer 26

tectonic plates move (producing new crust and recycling old crust) location of landmass influence: - ocean currents - solar radiation budget - precipitation

Question 27

link continental drift to ocean currents + impact

Answer 27

global ocean current = transport heat energy (surplus to shortage) continental drift can isolate or redirect oceanic currents: 1. changes direction of heat transfer 2. eliminate heat transfer region (ex of Antarctica)

Question 28

link continental drift to solar radiation

Answer 28

angle of insolation and energy distribution

Question 29

why do equatorial regions have greater rainfall than other lattitudes ?

Answer 29

because it is warmer!

Question 30

what are the types of movement are linked to orbital processes?

Answer 30

eccentricity obliquity (tilt angle) precession (tilt direction)

Question 31

what is eccentricity?

Answer 31

changing distance between the earth and the sun as the earth orbits the sun

Question 32

what are 2 things that the orbit path influences?

Answer 32

- solar radiation on earth - lengths of seasons

Question 33

what does a greater tilt (obliquity) induce?

Answer 33

greater extreme between seasons

Question 34

what is precession?

Answer 34

it is the direction of the tilt

Question 35

what is a Milankovitch cycle?

Answer 35

all changes in Earth's movement influence climate on a short geological time scale, during, changes in solar radiation amount and location can change to up to 25%