natural & anthropogenic changes

Question 1

what is earth temp regulated by

Answer 1

balance between how much energy comes in the system (sun) + how much goes out

Question 2

what is Heat absorbed by the Earth re-emitted as

Answer 2

longwave radiation (IR)

Question 3

what is the heat entering the system

Answer 3

the light that hits top of atmos and gets absorbed – some gets reflected and scattered away by tiny particles (droplets, dust etc)

Question 4

what 3 things is More long-wave radiation absorbed by

Answer 4

• CO2
• water vapour (clouds) - good at absorbing light
• nitrous oxides
  **all associated with climate change

Question 5

what is insolation

Answer 5

Radiation reaching surface

Question 6

what is albedo

Answer 6

insolation reflected by surface
Snow: high albedo, Soil: low albedo

Question 7

what happens to Radiation that’s reflected back off surface

Answer 7

absorbed in the atmosphere (Atmosphere: blanket keeping heat in)
- This reflected radiation is usually infrared & longer wavelengths
- H2O vapour & CO2 strongly absorb infrared

Question 8

what is CO2 accelerated by recently

Answer 8

• Greater industry activity: burning fossil fuels
• Deforestation & land clearance

Question 9

some stats about increase in global temp

Answer 9

• From 1959-2011: 24% increase in atmos CO2
• Between 1906-2005: Mean global surface temp increased 0.74oC
• Proportion of sea ice has decreased around 1/3 - less albedo + reflection of light – gets absorbed by sea instead

Question 10

where takes direct measures of [CO2]

Answer 10

Mauna Loa Observatory, Hawaii

Question 11

what’s used to take samples of CO2 concentration years ago

Answer 11

ice cores, coral drilling + tree rings

Question 12

what conditions can we see in High-mid latitudes + Low latitude

Answer 12

• High-mid latitudes = cold: glacials (ice ages) & interglacials
• Low latitude = warmer: interpluvials (dry) & pluvials (wet)

Question 13

name Milankovitch’s 3 astronomical cycles

Answer 13

• axial tilt
• Eccentricity of the Orbit
• Precession of the Equinoxes

Question 14

what does Milankovitch’s 3 astronomical cycles explain

Answer 14

the drives of glacial cycles - cycles between warm & cold periods
- 3 factors that control sunshine reaching high N latitudes: ~20% light variation

Question 15

what does the axial tilt explain

Answer 15

• Tilt of Earth’s spin – what causes seasons
• ~21.5o to ~24.5o and back every 42k years
• More intense/defined seasons in both hemispheres – bigger tilt

Question 16

what does Eccentricity of the Orbit explain

Answer 16

• Orbit circular, elliptical & back ~100k years
• If jupiter + saturn are to one side and pulling in the same direction it elongates that orbit to one side
• Weaker effect on seasonality than axial tilt
• Intensifies seasons in one hemisphere + Moderates seasons in the other hemisphere

Question 17

what does Precession of the Equinoxes explain

Answer 17

• Wobble of spin axis + effect of tidal pull of moon and sun on the earth - causes planet to slightly wobble
• Interplay between the 1st two factors
• Increases or decreases the tilt of the planet – intensifies or weakens seasonal variation

Question 18

what’s the problem with believing Milankovitch’s 3 astronomical cycles

Answer 18

No independent record of ice age timing – need to try get this from the sea

Question 19

what allows us to track what’s going on in terms of temperature

Answer 19

Ratios in O2 isoptopes (O16, O18)

Question 20

why do we use O2 isoptopes to track temperature

Answer 20

• Tend to have < O18 in ice than normal water
• 18O/16O in SW tracks ice volume on land
• H2O vapor: 18O precipitates more readily than 16O
• 18O evaporated from ocean less likely to travel from source than 16O
• Oceans enriched with 18O during glacials

Question 21

how can we use O2 isoptopes to track what’s going on in terms of temperature / ice ages

Answer 21

• Foraminifera use 18O/16O for their CaCO3 tests (shells)
• Die, sink, bury O signature in sediments
• Record of 18O/16O from forams in deep-sea cores:
• Ratio fell & rose in accordance with Milankovitch cycles
• Found Ice volume peaked every 100K yrs: eccen of orbit
• Other 2 cycles (23Ky & 41Ky): wrinkles
• Shows temp is varying because of these cycles

Question 22

how can we link temp with atmospheric CO2

Answer 22

• Analysed CO2 in ice core bubbles from Antarctica & - Greenland – looks at ratio of CO2 : N + O2 in the air bubbles on the ice
• V good correlation between CO2 & temp
• Low temp: result of low CO2

Question 23

how can we Link temp with ocean CO2

Answer 23

• Oceans regulate atmospheric CO2
• Ocean can act as large CO2 sink & hold 50-60 times more CO2 than the atmosphere
• Oceans = powerful CO2 pump - more efficient during glacial periods

Question 24

how does ocean control the global climate

Answer 24

great ocean conveyer belt
- Warm water gets drawn from gulf of mexico, over the north atlantic to northern europe – that heat gets released into atmosphere
- NADW floods deep Atlantic, distributes around other oceans

Question 25

what might drive the earth to further increase in atmos CO2

Answer 25

• Milankovitch Cycles major driving force – but happens in long periods
• Human perturbation = big consequence – rapid and severe changes in system
• However: Gradual changes in external forcing lead to ABRUPT & SEVERE alterations in climate

Question 26

what are the evidence that the rise in atmos CO2 could flip climate

Answer 26

• Over past five decades: increased freshening of Nordic seas – melting sea ice, increased rainfall
• Leads to Slowed NADW formation that drives the thermohaline conveyer
• Overflow decreased 20% since 1950
• Future: worsen with increase in CO2 + temp
• Accelerated melting of Greenland ice sheet
• Continued freshening: collapse of Atlantic Thermohaline Circulation?
• Models suggest 45% collapse by 2100 if CO2 emissions not cut
• Rapid cooling of NW Europe ??

Question 27

2 reasons ~30% anthro CO2 taken up by oceans

Answer 27

1) Increased atmos CO2
2) Increased PP & organic sedimentation