final exam EESC 105 Flashcards
how do we study Earth’s history?
- sedimentary rocks
- ice cores
how do greenhouse gases warm the Earth?
they trap outgoing IR and re-emit in all directions causing an energy imbalance so temp must rise to rebalance
climate sensitivity
- the amount the temperature will increase for every doubling in CO2
- expected 2-5ºC but difference mainly depends on timescale
what is the largest carbon reservoir?
geological reservoirs (rocks)
geological exchange with atmosphere
- very slow
- source: volcanic outgassing (releases CO2 from rocks)
- sink: chemical weathering (pulls CO2 out of atmosphere and into rocks)
sedimentary rocks
- they are formed at Earth’s surface influenced by environment
- deep ocean sediment, foraminifera (carbonate shells), coccolithophores (algae), fossils
deep ocean sediment
- forms gradually and laid down over time
- can go back 200 million years, mainly go back 100 million years
- integrated ocean drilling project collected hundreds of cores in past 20 years
foraminifera
- forams are carbonate shells that incorporate chemicals from seawater
- grown in different conditions and from there the ancient climate they lived in is concluded
coccolithophores
- phytoplankton
- grown in different conditions and from there the temperature they lived in is concluded
fossils in sedimentary rock
coral fossils indicate tropical conditions as modern corals only grow in warm tropical water
ice cores
- thickness of the ice can tell the length of time of ice accumulation
- ice traps ancient air
- can only go back about 1 million years
what did ice ages look like?
- northern hemisphere permanent ice sheet extended into US and Northern Europe
- southern hemisphere ice sheet looks pretty similar to today
what drove the ice ages?
orbital forcing (Milankovitch Cycles): obliquity, eccentricity, precession
obliquity
- Earth’s tilt
- the larger the tilt, the stronger the seasonal cycles of temperatures will be
- changes on a 41,000 year timescale
eccentricity
- degree to which Earth’s orbit deviates from a perfect circle (how elliptical the orbit is)
- changes of a timescale of 100,000 years
- affects how the incoming sunlight is spread through the year
- causes perihelion and aphelion
precession
- Earth’s wobble (changes the direction of the Earth’s tilt not the degree of tilt; Earth’s axis changes direction)
- changes on a 23,000 year timescale
is Earth’s orbit constant?
- Earth’s orbit is not constant
- orbital parameters change because if gravitational interactions between Earth and the other bodies in the solar system
- the changing parameters affect the distribution of solar energy around the globe
perihelion
- closest distance to sun during orbit
- currently at Northern hemisphere winter
aphelion
- furthest distance from sun during orbit
- currently at Northern hemisphere summer
if aphelion occurs at Northern hemisphere summer, why aren’t summers hotter in Antarctica than in the Arctic?
Antarctica is colder due to elevation and it has a higher overall albedo
how do precession and eccentricity relate?
- they go hand in hand
- no difference in configurations when Earth’s orbit is exactly circular even w/ the changing direction of the axis because all points in the orbit would receive the same amount of insolation
how can the climate change by orbital forcing?
- the total incoming solar energy doesn’t change but the spread through the year and across the planet changes
- main impact: producing better/worse conditions for ice sheet growth
optimum conditions for an ice age
- need to focus on Northern hemisphere summers as ice sheets can grow there (N. hem winters are cold enough so really only depends on making summer as cool as possible)
- lowest axis tilt means smaller seasonal variations (won’t get too hot in the summer)
- for precession, want N. hem summers at aphelion so furthest from sun
- high eccentricity so precession can make a big difference
last deglaciation
- northern summer insolation increased (due to orbital variations)
- this triggered ice sheets to melt
- warming worsened due to ice-albedo feedback
- CO2 buildup in atmosphere due to warmer oceans outgassing CO2 due to the lower solubility of CO2 w/ higher temps
- led to rapid warming and further CO2 release
- the warmer climate also is wetter and less windy which reduces the iron supply to phytoplankton thus slowing down their growth and weakening the biological pump
- this data is collected from ice cores
what levels did CO2 vary between during glacial and interglacial periods?
- interglacial ~280ppm
- glacial ~180 ppm, 5ºC cooler
how does the biological pump work?
- marine ecosystems pump CO2 to deep ocean where it is locked and can’t exchange w/ atmosphere which leaves surface undersaturated
- more CO2 is then absorbed by ocean to return to saturation (equilibrium)
de glacial iron limitation
- dust supply is enhanced in cold, windy, dry climates like an ice age
- dust supply declines during deglaciation
- southern ocean productivity declined and CO2 was released from ocean
- positive feedback loop is created
ocean iron supply
- Southern ocean has lowest dust deposition anywhere in the world
- dust carries iron
- plankton need iron to grow so iron is a limiting factor to plankton growth and carbon uptake in the southern ocean
cretaceous climate
- high volcanic activity
- sea level higher by 120-140m
- CO2 levels between 1200ppm
- 10ºC warmer on average
- poles and continental interiors never freeze
- tropical forests and fauna spread to poles
- extinction of polar species
what affects sea level?
- thermal expansion which means seawater expands when heated
- ice sheet melt
- volume of ocean basis which means when ocean ridges are spreading, they are broader and take up more space
sea levels in Cretaceous
- sea level higher by 120-140m (know this from chalk deposits)
- thermal expansion, rapid spreading of ocean ridges from tectonic movement, ice sheet melt
holocene period
- most recent interglacial period
- includes end holocene climate and anthropocene
end holocene climate
-climate reconstructed from tree ring records and historical/instrumental records
- includes medieval warm period and little ice age
- these events are often used as examples in the argument that climate changes naturally so we can show we that we understand the natural processes, and they are not responsible for recent warming
medieval warm period
- global average slightly warmer than pre-industrial by 0.2ºC
- period of stronger solar activity
- as mid-atlantic warmed, vikings were able to voyage further
- more regional impacts than global
little ice age
- global average was about 0.5ºC cooler than pre-industrial
- period of much weaker solar activity
- Europe and North America were much cooler
- artwork helped show what climate was like
- caused issues globally like dynasties falling, military death from storms, food riots from failed harvests
anthropocene
-eras when Earth has been dramatically perturbed by humans
what happened to the vikings during the little ice age and why is this important?
- vikings could not adapt to cooling climate and died out
- Native Americans already living there survived just fine because their culture was steeped in traditions and technologies from long before the Medievel warm period
- shows that climate is important part of how a civilizations grew and going outside of climate range experienced we’ve experienced across history is dangerous
what drove the climate changes during the end holocene period?
- changes in sunspots which affects the amount of solar activity
what are sunspots?
- dark patches that grow on sun’s surface
- regions of intense activity where solar flairs are common
what has the paleoclimate taught us?
- largest climate shifts in Earth’s history have been driven by CO2
- smaller shifts driven by factors like sunspots
- changing atmospheric CO2 naturally takes millions of years from geological reservoirs or thousands of years from the ocean
- relatively small climate shifts have large impacts on human civilizations (little ice age)
- CO2 changes similar to those we expect to see in next 100-300 years will have huge impacts on sea level
general overview of fuels and energy
- atmospheric CO2 has risen since 1750 when industrial revolution began
- rate of increase has increased
- coil, oil, and gas supply > 80% of energy worldwide
what are fossil fuels?
carbon-containing compounds that can be burned for energy
what are the different types of fossil fuels?
- coal
- oil
-natural gas
coal
- from terrestrial plants
- made mainly in swamps
- anoxic conditions prevented decomposition + time, pressure, and heat to turn into hydrocarbons
- impurities w/in coal grades come from sulfur, nitrogen, and mercury
energy in creation of fossil fuels
- energy from pressure and heat is put into the plants to go from oxidized to reduced
- that same energy is the energy released when it is burned
oil and natural gas
- forms in coastal regions (sea shelves w/ high biological activity)
- derived from algae (dead plankton)
- matter is preserved in anoxic sediment
- oil forms on top with heat, time, and pressure
- gas forms below with more heat
- coal is a mixture of hydrocarbons and alcohols
- gas is mostly methane
why is oil and gas hard to obtain?
- they’re spread out too thinly in sedimentary rocks
- has to naturally concentrate so an oil/gas well can be tapped
energy yield
the amount of energy a system produces in its actual operating environment
what is the reason for energy yield?
- want as many Hydrogens per unit C
- the hydrogens will oxidize to H2O so less bonds with carbon therefore less CO2 is released
energy yield of coal
- least amount of hydrogen bonds
- thus dirtiest because releases most amount of CO2
energy yield of oil
between coal and gas
energy yield of gas
- most amount of hydrogen bonds so most amount of hydrogens can be oxidized
- least Carbon per unit energy