EARTH HISTORY 2Changes in Atmosphere
ppt. by Robin D. Seamon
CLIMATE VARIABLES
It’s all connected! Changes in one affects the other:
CLIMATE CHANGES
Atmosphere: gas layer of the earth; it’s where weather happens
Climate: weather patterns shown over time
** if the atmosphere changes so does the climate**
QUESTION: What creates change in climate?
ANSWER: Changes in atmosphere
1. Biotic processes (life) **• Respiration: breathing in/out O and CO• Transpiration: release of H 0 and CO • Waste products• Recycling of gases after death
2 2
2 2
• Life affects gas cycles:• Carbon Cycle• Water Cycle• Cloud formation• Weathering
EXAMPLE:2.4 bya The Great Oxidation Event (put oxygen into atmosphere)
http://guardianlv.com/2014/02/australian-crystal-found-is-4-4-billion-years-old/
2. Variations in solar radiation• amount affects photosynthesis, precipitation,
wind patterns, temperature (AFFECTS LIFE)• Sun has cycles of solar
storms (flares) & sun spots which couldaffect earth & it’s life
EXAMPLE: 1550-1850 Little Ice Age
Thames River: HENDRICK AVERCAMP'S LITTLE ICE AGE
3. Plate tectonics• shape of the
continents determine ocean & wind currents
• How heat is transferred
• How much moisture
http://www.bgs.ac.uk/discoveringGeology/climateChange/general/causes.html?src=topNav
EXAMPLES:• Mountains vs. plains• Large continent vs. several smaller ones• Connection of two continents block off
ocean currents- Isthmus of Panama
• IN PAST- tectonic movement caused big storage of Carbon- fossil fuels
TODAY: Coal mines
Carboniferous Era
4. Volcanic eruptions & LIPs• spew gases into the atmosphere-
changes chemistry (LIFE)
http://www.bbc.co.uk/news/world-asia-29399306
Mt Ontake9/27/2014
• LIP- large igneous provincesPlaces where igneous large rock beds indicate a flow of lava from cracks in the crust
• Can block out sunlight, preventing photosynthesis (LIFE)
• Meteor induced
http://news.nationalgeographic.com/news/2013/13/130212--chicxulub-asteroid-dinosaurs-volcano-mass-extinction-environment-science/
MODERN EXAMPLES:1815 Mt. Tambora: Year without a Summer1991: Mt. Pinatubo: global temp down 0.9˚F for 3 yrs
5. Cryosphere: ice layer
http://www.toppforskningsinitiativet.org/en/programmer-1/program-2
http://rramu0153.wordpress.com/
• During ice ages, sea levels are lower • water/run-off is trapped in ice • not in water cycle = DRIER
• Albedo: amount of ice affects temperature:• more ice: more sunlight is reflected back
off Earth• less ice: Earth absorbs more solar Energy
• Carbon sink: ice keeps dead organisms from decomposing (more carbon) is absorbed than released
http://www.earthgauge.net/2011/system-dynamics
6. Milankovitch Cycle variation in intensity of sunlight due to slight variation in Earth’s orbit
• Pace setter for cycles of warming & cooling
http://www.bgs.ac.uk/discoveringGeology/climateChange/general/causes.html?src=topNav
http://www.southwestclimatechange.org/figures/milankovitch
Orbital shape: (eccentricity)
Earth’s orbit changes from it’s elliptical
shape; 100,000 yrs
Orbital axis wobble:
Changes in tilt causes strength of
seasons20,000- 40,000 yrs
7. Greenhouse Gases• More greenhouse gases = thicker blanket,
holding in solar radiation (warmer)• Fewer greenhouse gases = thinner blanket,
trapping less solar radiation= (cooler)
http://www.ib.bioninja.com.au/standard-level/topic-5-ecology-and-evoluti/52-the-greenhouse-effect.html
• Natural Causes• Warm oceans absorb CO • Cold oceans release CO• CH (methane) from decay
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• Human contributions• Release of carbon into the air through
burning of fossil fuels & cement manufacture increases the greenhouse layer
• Aerosol increase (tiny particles in atmosphere)
http://en.wikipedia.org/wiki/Climate_change#mediaviewer/File:NSFmonsoonsandclimatesince200AD.jpg
Human civilizations affected by climate changes:
PALEOCLIMATOLOGY-study of ancient climate
How do scientists measure atmosphere from earlier in Earth’s history?
Radiometric Dating in:Rocks & sediment
• Sea floor cores composition & past temperature
• Loess composition& past temperature
Ice core data• Layer size, pattern, & • Composition
Ancient Fossils
foraminifera in ancient sea beds
Glaciers –moraine sediments
Evidence left of past sea levels• On shore• In ancient
coral beds
HISTORY OF PALEOCLIMATOLOGY
Pleistoscene Epoch: most recent Epoch in Earth’s history- glacier cycles• Before that: long eras of warm climate
Late 19th Century:• Patterns were seen, but tools not there to date
stuff
• Palynology: study of pollen• Each species distinctive &
durable• Show patterns of where
plants lived in the past• (hot-cold range)
SO SCIENTISTS STUDIED:
• Saw fossil hoards of nuts showed hazel trees farther N 5,000 yrs ago
• Sea level change:• (ice locks up ice from water cycle, lowering
ocean levels during Ice Ages)• Coastal crust showed sea level changes
with a long time between Ice Ages
??? How were Ice Ages triggered???
• Traditional View: Earth only had 4 big glaciations, based on surface strata
• Moraines: rocks & sediments carried & deposited by a glacier at its farthest edges
http://www.mediahex.com/Moraine
• Astronomy 1920’s & 1930’s• Milutin Milankovitch’s Theory (Serbian)Saw patterns in Earth’s orbit that he thought coincided with Ice Ages in Earth’s past• 20,000 yr cycle (inclination)• 100,000 yr cycle (eccentricity)• Conflicted with traditional view so most
scientists dismissed
Reliable Dates & Temperatures 1955-1971• Absolute dating- new tool: radiometric dating
• Cesare Emiliani (Italian) 1955 recorded temp variations from the amount of oxygen in ancient sea shells
• Said patterns matched Ice Age cycle predicted by Milankovitch
• Didn’t match the Big 4 glaciations• Needed to dig farther for pattern?
• Wallace Broecker (US) 1968 studied ancient coral reef beds
• Different elevations showed that the sea levels went up and down with Ice Sheets
• Used radiometric dating Uranium• Matched Milankovitch cycles
• George Kukla (Czech Republic) 1977 studied loess to confirm existence of dozens of Ice Ages
• Loess wind-blown dust accumulations that were found in clay quarry on land
1. Sea level changes2. Temperature of deep sea cores
SO: Orbital variations verified in:
??? How could something as small as angle of sunlight cause ice Ages???
• Global Cooling: 1970’s Emiliani predicts start of a new Ice Age soon
• He warned that greenhouse warming caused by humans could overwhelm orbital shifts
• Magnetic Reversals: new dating technique verified age of rocks & core samples being studied
Ice Core Samples• Samples of ancient air!• Show past atmosphere composition• Show aerosols (small particles in air)• Scientists can count layers yearly• Can be checked with major known
eruptions (like Pompeii in 79CE)
• Ratio of oxygen in ice can measure temperature inside cloud it was formed
• (warmer air= heavier isotope of O)
• 1950’s US Camp Century created in Greenland (Cold War)
• 1966 -1 mile down• Ice core showed last 100,000 yrs
THEORIES CONFIRMED 1971-1980:
• 1968 US Byrd Station created in W. Antarctica• Confirmed Ice Age happened at same time in
N & S (GLOBAL GLACIATION)
• Showed same saw-tooth curve pattern seen in deep sea cores:
Brief warmth
Longer cold
http://www.skepticalscience.com/trend_and_variation.html
Nicholas Shackleton 1973 used magnetic reversal dates & deep core samples • Confirmed sea levels coincides
with Ice Sheets• matched Milankovitch cycles
• deep sea drilling• loess
SO: 100,000 yr cycle verified in:
• Earth’s climate system has evolved in the past so change is possible
• Feedback mechanisms: natural responses that add to the system
??? How was Milankovitch Cycle a pace maker to trigger Ice
Ages???
??? What were the feedback mechanisms that amplified the
Mil. Cycle???
• 1980’s scientists noticed CO levels went up or down with the temperature in the past
• Russiann Vostok Station (1957 +) cores• CO & CH during Ice Age• CO & CH in warm periods
??? GAS KEY ???
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2 4
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• 1980’s global warming becomes a political issue
??? Could swing in greenhouse GASES amplify orbital shifts ???
• Greenhouse warming & other human influences strong enough to change the natural trend
• Could launch Earth into a wholly new climate trend (new pattern)
• Climate Sensitivity CO levels in past 750,000 yrs at 180-280 parts per million
• In 2012: levels were at 400 ppm and rising (methane too)
2
FACTS:
Scientists Warn:
http://www.science20.com/virtual_worlds/blog/is_global_warming_really_a_recovery_from_regional_cooling-121820
http://www.forbes.com/sites/alexknapp/2013/09/10/the-daily-mail-is-wrong-the-earth-keeps-warming/
SEA ICE
SEA LEVEL
Changes in Feedback?• In past glaciations it appears that:
• Sunlight • Temperature • CO & CH from oceans
Making a warming loop until Mil. Cycle
turns the cycle towards cooling
2 4
CO & CHincrease
2 4Ice melts-albedo
decreases
Temperature increases
Temperature
CO & CH 2 4CO & CH 2 4
Temperature
FAST
ER
SLO
WER
THEN orbital shift:• Sunlight • Temperature • CO & CH from oceans
Making a cooling loop until Mil. Cycle turns
the cycle towards warming
2 4
CO & CHdecrease
2 4Ice forms-albedo
increases
Temperature decreases
decreased
IN THE PAST: • Temp increased b/c of sun angle shift • Sun angle shift started the loop, increasing the
greenhouse gases & warmth
NEW:• Orbital shift isn’t triggering the warming trend• extra greenhouse gases are starting the process• NOW- CO levels are increasing the
temperature first2
NEW:• Gas levels rising faster than anything seen for
millions of years & natural feedbacks are kicking in
• Drying forests• Warmer seas• Methane from Arctic melt
CONCLUSION• Geological record verifies with independent
methods & data the process computer models are predicting:
• Disruption of climate from its recent patterns
??? What will the changes be??? This is where the
ARGUMENTS BEGIN…
RESOURCEShttp://www.aip.org/history/climate/cycles.htm
http://en.wikipedia.org/wiki/Climate_change
http://www.bgs.ac.uk/discoveringGeology/climateChange/general/causes.html?src=topNav