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GOPH375 > Ch 12 > Flashcards

Ch 12 Flashcards

1
Q

Volcanism, Mountain Building, and Tectonics

A

Volcanism - major source of CO2 to the atmosphere
Mountain building - more rock weathering removes CO2 from the atmosphere, binds up in limestone
Tectonics: negative feedback maintains climate equilibrium

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2
Q

Climate History of Earth: Sedimentary Rocks

A

Warm climates:
- fossil reefs, limestones
- Al ores in tropical soils
- Salt beds from inland sea evaporation
Cold climates:
- Glacial erosion leaves distinctive marks and debris deposition

18O and certain fossil organisms indicated paleo-temp history of Earth’s climate

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3
Q

Oxygen Isotopes and Temperature

A
  • Use ratio of stable isotopes of oxygen in CaCO3 sea life fossils
  • Evaporation removes more light 16O, and leaves behind more heavy 18O
  • Atmospheric water becomes depleted in 18O
  • 18O depleted water is trapped on land as snow or ice during Ice Age -> marine organisms use 18O rich water to make their shells
    Measurement of 18O/16O in CaCO3 fossils is an indicator of climate when organism lived
  • High 18O/16O -> colder climate
  • Low 18O/16O -> warmer climate
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4
Q

The Last 3 Million Years

A
  • Old, stable ice sheet on Antarctica
  • North American and Eurasian ice sheets expand and shrink, affecting global climate
  • Forming of Isthmus of Panama 3mil ya blocked westward-flowing ocean water, forcing it north
  • Warm water in north Atlantic Ocean increased evaporation and snowfall to build glaciers
  • Continental ice sheets in Northern Hemi undergo complex cycles of advance and retreat
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5
Q

Orbital forcing of climate in Milankovitch cycles

A

Orbit, tilt, and wobble
Orbital eccentricity:
- 100k year period
- More circular to more elliptical
Tilt of Earth axis:
- 41k year period
- 21.5 to 24.5 degrees
Precession of tilt:
- Bimodal period 23,000 and 19,000
- Wobble

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6
Q

The Last Glacial Maximum

A
  • 20k years ago, covered 27% of today’s land
  • Sea level was lowered 130m to build glaciers
  • Current Ice Age continues (current glacial retreat)
  • 10% of continents still buried under ice and sea lvl would rise 65m if all the ice melts
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7
Q

Temperature since 20k ya based on Greenland ice-core oxygen isotopes:

A
  • Warming began, then interrupted by a cold stage
  • Cold interval replaced by warming period
  • Temps fell through a different interval and bottomed from 12,900 to 11,700ya
  • Then current interglacial period
  • Temp changes of 3-5C occurred in several years
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8
Q

Cause of sudden drops or jumps in temperature:

A
  • Melting of continental ice sheets left behind huge cold lakes with ice dams
  • Failure of ice dams released lots of fresh, cold water into surface layers of ocean = disrupted oceanic circulation
  • Megafloods of cold, freshwater into arctic prevented sinking of arctic water -> shuts off influx of warm surface waters from equator
  • Constant rise in sea level from melting of glaciers
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9
Q

At 7k ya:

A
  • Warmer global temps, higher rainfall totals -> climatic optimum
  • Since then, average global temps have fallen 2C
  • Smaller cycles of glacial advance and retreat within cooling trend
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10
Q

El Nino

A

Warm ocean water arrives at Peru and Ecuador near Christmas time

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11
Q

La Nina

A

Occurs when cool waters move into the equatorial Pacific
- Brings cold air and high rainfall to NW US and western Canada, below average rainfall to rest of North America
- Encourages hurricanes in Atlantic Ocean, low rainfall and wildfires in SW US

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12
Q

Pacific Decadal Oscillation

A

Last 20-30 years
Mid-latitude Pacific Ocean conditions, 2º tropical effects
- El Nino lasts 6-18months, condition of tropics, 2º effect on mid-latitudes
Warm phase with more storms and rainfall
Cold phase with less storms
Unknown mechanistic cause

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13
Q

Volcanism and Climate

A

Large Plinian eruptions blast fine ash and gas to the stratosphere
- Above the troposphere where weather occurs
- Not washed out quickly by rain
- Floats for years
Ash and sulfuric acid (from SO2 gas) remain in the stratosphere as a haze, blocking some incoming solar radiation = climate cools

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14
Q

Worst-case scenario: flood basalt eruptions (66mil ya)

A
  • 2.6mil km^3 of basaltic lava erupted in only 700k years
    Possible effects:
  • Increase in atmospheric CO2 -> temp increase of 10C
  • More acidic ocean waters
  • Depleted ozone layers
  • Punishing to life on land and in surface ocean
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15
Q

Mayan Civilization and Climate Change

A
  • Successful in agriculture, irrigation, social organizations, mathematics, and astronomy over 1k years
  • Centuries-long pattern of decreased rainfall -> drought -> abandonment of urban areas, stop in monument construction, breakdown of social and political order -> wars, return to a life of rural subsistence
  • Significant decline in civilization due to string of events triggered by long-term climate change
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16
Q

Past Thousand Years

A

Combined effects of eccentricity, tilt, and wobble caused a cooling trend with numerous variations
Other variations within cooling trend being studied with:
- O isotopes in glacial ice layers
- Annual growth rings of corals
- Tree rings
- Tax records of grain and grape crops
- Advances and retreats of mountain glaciers
- Paintings of frock lakes, rivers, ports
- Weeks/year of sea ice around Iceland

17
Q

Medieval Maximum:

A

warm period from 1000-1300CE

18
Q

Little Ice Age

A

The cold period from ~1350-1850CE
- Smaller scale cooling and warming within this
- NE Canada had permanent snowfields
- Shortened growing seasons in Europe with localized famine
- Potential causes: volcanic eruptions, changes in ocean circulation, reduced solar energy

19
Q

Current hypothesis for Little Ice Age

A
  • Volcanic eruptions in 1200s added aerosols to the atmosphere = lower solar radiation at surface
  • Climate cooled and glaciers advanced
  • Sea ice-cooled and warm water circulation to North Atlantic was shut off
20
Q

Maunder Minimum:

A

cooler period from 1645-1715CE
- Minimal sunspot activity -> sun possibly 0.25% weaker

21
Q

Processes altering climate in past 1000yrs, changes to:

A
  • Earth’s orbit
  • Volcanic eruptions
  • Solar energy output
  • Sea-surface temp in tropics
  • Aerosol [ ]s
  • GHG [ ]s
  • Interactions among above processes
22
Q

20th Century

A
  • Began as warm as any time in past 1000yrs
  • Warming unprecedented in recent past
  • Solar output responsible for less than 10% of warming
  • Major causes of warming: GHGs and aerosols
  • Avg global surface temps rose 0.6ºC in 20th century from 1910-1944, and since 1977
  • 1910-1944 warming: hotter Sun, lack of volcanism
23
Q

Warming since 1977 twice that of 1910-1944: due to GHG buildup

A

Natural causes 0.2ºC:
- Changes in Earth’s orbital patterns -> -0.02ºC
- Hotter Sun -> +0.22º
Human activities 0.4ºC increase

24
Q

Start of 21st century:

A
  • Rate of annual temp increase declined, then all-time highs in 2014, 2015, 2016
  • Annual temps since 1977 have all exceeded 20th century avg annual temp
25
Q

Majors GHGs:

A

H2O vapour, CO2, CH4, N2O, O3, and CFCs

26
Q

GHGs

A
  • GHGs absorb energy radiated from Earth, keeping it from escaping into space
  • GHGs are increasing in atmosphere
  • Effects of CO2 and CH4 are well understood
  • Size of feedbacks from increasing water vapour or aerosols are less well understood
27
Q

Non-condensing GHGs are well mixed in atmosphere:

A
  • Remain in atmosphere for centuries
  • Stabilize temp structures that sustain water vapour and clouds
  • Without them, climate would cool to icy state
28
Q

CO2

A
  • Causes about 60% of greenhouse warming by humans
  • CO2 removal from atmosphere:
    ○ 20% = photosynthesis
    ○ 30% = ocean dissolution
    ○ 50% = stays in atmosphere
29
Q

CH4

A
  • Causes ~16% of greenhouse warming
  • 21x higher heat-trapping ability than CO2
  • 700ppb in 1750 to 1835ppb in 2017, slow increase in 19th century and rapid in 20th
  • Released during decomp of vegetation in O-poor environments: swamps, rice paddies, cattle digestive systems
  • ~40% natural release, primarily from wetlands, termites, “mud volcanoes”
  • Human emissions: fossil fuel burning, rice growing, livestock, landfills, wood burning, etc
30
Q

N2O

A
  • ~70% produced naturally by bacteria removing N from organic matter, esp in soil
  • ~30% produced by humans in agricultural activities
    ○ Chemical fertilizers
    ○ Combustion of fuels in vehicle engines
    ○ Atmospheric lvls are increasing regularly and rapidly
31
Q

20th Century GHG Increases

A
  • Byproducts of industrial and domestic energy prod, rice and livestock agriculture
  • Population doubled twice
  • Lifestyle of industrialized world
  • Pop continues to grow -> GHG buildup is continuing problem
32
Q

Climate Consensus for 21st Century

A
  • > 90% increase in global temp due to human GHGs
  • Prob of global warming by natural changes only <5%
  • World temp could rise b/w 1.1-6.4ºC during 21st century
  • > 90% prob of more frequent warm spells, heat waves, and heavy rainfall
  • > 66% prob of increased droughts, tropical cyclones, and extreme high tides
  • Sea lvl will rise 18-59cm
  • Past and future CO2 emissions will continue to contribute to warming and sea-lvl rise for >1000yrs

GOPH375 (10 decks)

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