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Terms in this set (58)
True or False: The Earth was once completely covered in ice
True: "snowball earth" covered in ice from pole to pole
True or False: The Earth has had hotter climates than what global warming will face?
True: had extreme got climates to melt ice
What sets the climate over Earth's history?
the sun, orbit of the earth around the sun, locations of the continents, volcanoes
How does the sun set the climate over the Earth?
changes in magnitude over its lifetime
over the last billions years, the sun has increased by 10%. Initially was 75% as strong as it is now
How does the orbit of the earth around the sun set hte climate over the Earth?
if the solar system was just the earth and the sun, the orbit would be a perfect ellipse that never changed
How does the locations of continents set the climate over the Earth?
these have shifted with time
Mountain ranges appear, sometimes high latitude ice sheets aren't possible
How do volcanoes set the climate of the Earth?
on short timescales: cooling from aerosols
on long timescales: adds significant amount of CO2
How do we know about paleoclimate?
Proxy, biological, ice core, geological, and isotopic data
tells us about temperature, precipitation etc through other indicators
uses things like tree rings, pollen, corals, and fossils to make assumptions.
Ex: alligator skeletons at high latitudes tell us that the winter ocean temperature must have been very mild
Ice Core data
ice at the bottom of Greenland/Antarctica over 100,000 years old
ex: ice cores have tiny bubbles of air trapped inside that show past atmospherice compositon
rocks, sediments, shape of the land
Ex: land in Seattle area is cut out by glacier flows from ice sheets that must have had much larger extent
tell us about precipitation and temperature
What does all the data from paleoclimate information have in common?
all can be dated by the use of carbon dating or radiometric data
What's the equivalent of earth years to a 20 year old person?
lifetime of Earth (4.5 billion years) to whole life
past 250 million to last year
million years to last 36 hours
20,000 years to last 45 minutes
How has the temperature changed over time?
"deep" (distant) past was mostly warmer than today
What is the "Faint Young Son" Paradox?
sun was initially 75% as strong as it is now
passed by Carl Sagan in 1972
Earth was warm most of the time when it was weak
How do we know the sun was weaker?
rounded pebbles, mud cracks, apple marks, microfossils
increase of greenhouse gas concentration (methane likely) to keep it warm
How would the earth be snowballed?
billion years ago when ice-albedo feedback spiraled out of control
high albedo and low temperatures
How would the snowballed earth melt?
extremely high greenhouse gas
Why are volcanoes efficient with CO2 output?
important over 100,000 years
How can CO2 be removed over time?
chemical weathering: rain/snow falls on silicate rocks, reacts and takes Co2 out
Why is chemical weathering a negative feedback?
when climate is hotter it's easier to take it
likely key for stabilization of climate over millions of years
How could snowball earth happen?
volcanic activity injected CO2 into atmosphere
land and oceans covered by ice; no chem weather to remove CO2 from atmosphere
How did it melt?
became so strong that ice melts even w high albedo
How would earth change after snowball?
CO2 increase tremendously
hottest period in Earth's history right after the coldest
massive weathering could gradually decrease CO2 and temp
How would life survive during snowball earth?
unsure, cracks in the ice, hydrothermal vents, blue ice
What are the true statements about warm climates?
hotter in past than we'll have with global warming
planet and life will survive
warmer periods start with massive extinctions
What is the Great Dying?
Permian-Triassic extinction: 25 million years
90% of marine species die
2/3 of land die
Why did the Great Dying happen?
quick onset -> greenhouse gas -> warmer oceans
How were CO2 levels in the past
higher than present
many lines of evidence (isotopes, rocks/fossils, examine of plant fossils, carbon cycle models)
Why was there an increase in CO2 ?
increase in undersea volcanic activity (plates separate more quickly back then= increase in volcanoes)
How can you tell land was underwater?
chalk deposits from shells in inland seas (cretaceous=chalky)
sea levels were 200 m higher than today
mid N. America was covered
Why were sea levels so high?
no ice sheets
thermal expansion of sea water
ocean was less deep (tectonic activity)
How was the climate after cretaceous?
warm climate persisted
Paleocene Eocene Thermal MAximum
55 million years ago = quick jump in temp
same time as pockmarks on ocean floor = methane hydrate release
Why were there mini animals?
shed heat faster while temperature rose
What was the role of the continental drift in climate?
-movement of Antarctic over South Pole
-ice sheets form = increase planetary albedo
-decrease of CO2 starting 60 million years ago
-same time with increase of Himalayas and Rockies
-more weathering as fresh rock exposed
-slowdown in continental drifts
-less volcanism, less CO2
closing of the isthmus of Panama
Summary of the last 35 million years
earth slowly cools -> life retreats from poles -> polar ice caps established -> most recent ice ages begin (3 million years)
Cause of CO2 decreasing
Himalayas form when India collides with Asia and fresh rock and increase precipitation around mountains increase weathering
When did the ice age occur? and when?
lasted 27 million years to 10,000 years ago
large ice sheets covered NW Europe and Northern North America
Last Glacial Maximum (LGM)
occur 20,000 years ago
sea level was lower by 120m bc of storage of water in the continental ice sheets
How is ice used to tell the past?
ice sheets provide records of the past
ice cores: taken from Greenland and Antarctica
What can you gain from ice core evidence?
isotopic evidence = oxygen isotopes
O-16 = lighter and evaporates easily
O-18 = heavier, rains out easily
What do isotopes in ocean sediments show?
glacial ice volume in coves, local temperature
How can air bubbles show us info?
shows Co2 concentration and shows correlation with temperature
methane concentration decrease in ice age as well
why does air trap in snow show us evidence?
snow is convective due to melting, winds
diffusive can still be mixing of air bubbles
lock in zone traps these bubbles
Is CO2 the driver of ice ages?
CO2 was a feedback not a forcing due to temp change and it amplified this change
What is the real driver of ice ages?
change in solar radiation due to change in Earth orbit around the sun
How do interglacial events occur?
when there is more summer sunlight
onset of ice ages occur when less summer sun
What drives the ice age?
solar radiation in north hemisphere summer is key to growth/melt of ice sheets
colder summer = snow doesn't melt and can accumulate
(always cold enough in winter for snow at high altitude so winter doesn't matter)
How does a glacial age occur?
less sunlight in summer = colder summers and increase of high altitude ice sheets
How does the tilt of Earth make change?
currently: 23.44 deg
tilt is reason for the seasons
higher tilt makes summer hotter, winters colder in high latit.
currently decreasing tilt
Why is CO2 highly correlated with ice volume? Antarctica temp?
colder water can dissolve more atmospheric CO2
What is the Younger Dryas?
ex of rapid climate change
relatively cold period for 2,000 years
warmed abruptly for 12,000 and is now stable
What probably caused the Younger Dryas?
ice sheet breaking up and flooding in the northern north atlantic
melt water pulse could cause the thermohaline shutdown
decrease heat transport into northern N. Atlantic
What do tree rings tell us?
what does proxy data suggest?
little ice age and medieeval warm period were localized events in Northern Hemisphere