Natural Climate variation 7.1 Flashcards
The Greenhouse effect?
Greenhouse effect of earth is to do with radiation of Energy
-radiated energy from sun: reflected back or absorbed
-absorbed may later be re-radiated as lower frequency infra-red waves
-some is absorbed by gases of atmosphere > emitted downwards & re-absorbed by surface. This extra energy keeps earth 32 degrees warmer than with no atmosphere
Equilibrium= soon reached between input from Sun and losses into space
greenhouse gases? (3 Types)
Water vapour
- accounts for 35-70% of GHG on Earth
- warmer= more evaporation > even warmer from more vapour in atmosphere
Carbon Dioxide
- 10-15% of GHG
- Doesn’t form clouds, no counter effect
- If C02 levels rise > temps will rise
Methane
- 20 times more potent than C01
- 5-10% of our GHG
Causes of Natural Climate Change
Super Continents & supercycles?
Pangaea = continents joined as supercontinent Panthalassa = global ocean, whole ocean
The pre-pangaea continents came from breakup of previous super continent & a continuous cycle of breaking & coming together > super cycle
-eventually continents came together again by subduction on other side of world
Global Climate & Plate Tectonics?
Plate tectonics vital in balancing world climates & temps:
- volcanoes release heaps of C01
- subduction buries carbon containing rock
Scientists discovered:
- When theres a single supercontinent = climate colder, drier, low sea levels…
- because volcanic activity is minimal so C01 levels are lower > reduced GHG effect lowers earths temp
- Low temp = less evaporation, less rain. Formation of a permanent ice-cap lowers sea levels for many years. World > dry, cold, desserts with tundra at high altitudes - When many continents split up > more rifting & subduction > volcanic activity increases C01
- GHG effect increases global temp > more evaporation, rainfall
- more rainforests, coral reef systems
We are in-between these 2 situations
Other Planets Greenhouse effects?
Mars:
is freezing (-60) and no greenhouse effect > the core froze & all tectonics stopped
Venus:
is boiling (460) and greenhouse effect went out of control when explosion from build up of heat in mantle released insane amounts of C02
The Deccan Traps?
- In Indian, 500 000km^(2), 2000m deep
- ‘Traps’ > result of huge volcanic eruptions, on/off 3my
- caused by a mantle plume ‘hot spot’.
The Siberian Traps?
- Eastern Russia, 4 times larger than Deccan
- eruptions went for 1my
- caused by hot spot which melted through Asian tectonic plate
- hot spot believed to have created ice land
Eruptions, Impacts & Climate change…
- Both Deccan & Siberian associated with mass extinctions in past:
- Deccan occurred around ‘K-Pg event’
- Siberian blamed for ‘Permian-Triassic mass extinction’
Deccan & Siberian traps link to K-Pg event and Permian-triassic extinction?
K-Pg Event:
- 66mya, ‘donator killer”, wiped out 60% of life
- 10km asteroid hitting earth sent shockwaves that triggered volcanic eruptions (Deccan) on other side of earth > possibly due to seismic waves
The Permian-Triassic Extinction:
- 250 mya, wiped out 95% of life > blamed on climate change.
- However, evidence of asteroid strike into Antarctic…and the impact site is on the opposite side of Siberian trap
*From these events climate change happened
Volcanic Eruptions? (4 types)
Injection of Ash/Aerosols into Atmosphere:
-Blocks & reflects sunlight > cooling effect, reduces photosynthesis
Eruption of Acidic Gases into Atmosphere:
-volcanic gases (sulfur oxide) results in acid rain > kill forests, poison waters
Increased Levels of Greenhouse Gases:
-Volcanoes produce heaps of C02
Sea Levels Rise or Fall:
- Cooling effect > ice caps grow > seas drop
- Warming > ice caps melt > seas rise
Impacts from Space?
Inject Dust & Aerosols into High Atmosphere:
-leads to extreme cooling effect, lasts for decades
Create Huge Tsunamis:
-Mass destruction of land
Vaporisation:
-Vaporisation of billions of tonnes of rocks releases heaps of C01 > Greenhouse effect > warming
Create Thermal Shock Wave:
-This ignited massive fires globally>C02 released>warming
The Milankovitch Cycles (name 3)
Eccentricity
Axial Tilt
Precession
Milankovitch cycle: Eccentricity?
Earth orbit around sun is not circular, its oval
- when its more eccentric > summers hotter, winters cooler
- this cycles every 100 000 years
Milankovitch cycle: Axial Tilt?
The angle between earths orbit & its axis of rotation varies over 40 000 years
-this also effects extremity of seasons
Milankovitch cycle: Precession?
Third orbital variation is ‘wobble’ of earths orbit which affects how the cycle of seasons corresponds to the eccentricity of the orbit
