Term
| Was there a rapid transition from the Pleistocene to the Holocene? |
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Definition
-Wasn't instantaneous exactly 12k yrs ago
-Trnasition took time to melt glacial ice which lasted up until 6000 yrs ago w/ the Laurentide Ice sheet; Summer insolation had already peaked and was receding. |
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Term
| Why is the corridor between the Laurentide and Cordilleran ice sheet important? |
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Definition
| -Allowed migrants crossing the Beringia land mass to go through Canada into the Americas interior parts of continent. |
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Term
What was the Younger Dryas?
-when did it occur?
-Why was it named "Younger Dryas"?
-What sort of dating technique is used?
-How does this effect Milankovitch theory? Was it caused by earths orbit?
-What were some glacial conditions being indicated? |
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Definition
-It was a cold snap lasting around 1-2k yrs about 11-13k yrs ago.
-It was called Younger Dryas because the Dryas is a plant that grows on tundra or high alpine elevation sites, producing very distinctive pollen.
-Pollen records in Europe note tree pollen decrease rapidly and you begin to get pollen from cold adapted plants like Dryas.
-Doesn't adhere to Milankovitch theory, should be warming, nothing going on in earth's orbit to cause the cold snap.
-Conditions indicating a rapid re-glaciation were:
-decreased summer temps in greenland
-ice re-expanding in Scandanavia, Scotland & Europe.
-Lots of dust in atmosphere |
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Term
| Two theories of the Younger Dryas Event |
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Definition
-NOT MILANKOVITCH RELATED
1) As ice is melting it's producing huge amounts of cold, fresh melt water forming BIG glacial lakes; Biggest one being LAKE AGASSIZ. It can't melt northward because of ice acting as a dam but slowly ice retreats causing a catastrophic flow into the great lakes and out into the Atlantic.
-When you add HUGE amounts of FRESH COLD water to Atlantic, because it's fresh, it forms ice more readily changing the characteristics of the Atlantic and causing a massive freezing across the N. Atlantic.
-This affects the GREAT CONVEYOR ocean system; by putting cold fresh water in N. Atlantic it not only causes local freezing but changes ocean currents world wide.
-IN SUM: Laurentide ice sheet melts off forming glacial LAKE AGASSIZ, gets stuck behind glacial dam until it melts letting HUGE flow of FRESH WATER into Atlantic causing 1000's of years of ocean current disruption.
Theory 2(Controversial): Extraterrestrial impact of a meteor or comet on the Laurentide ice sheet caused catastrophic metling and draining into Atlantic.
-Evidence: High amt of iridium and charcoal in N. America caused by fires from impact.
-Side Note: Laurentide and Cordillieran Ice sheet only converge one time in Earth's History and it was during this time, SO this event may have squeezed water into the Lake Agassize without alternative flow to go.
-KNOWN: Atlantic had HUGE amounts of COLD FRESH WATER introduced abruptly. |
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Term
| Why at the end of last ice age did the massive fauna all disappear? Climate change on environment? Clovis? How did humans arrive? Kill Front theory? Trophic Cascade? Additional pressures? |
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Definition
-Environmental Change? Problem w/ that is there have been lots of transitions from ice ages to warmer planet and they went through fine.
-Most megafauna disappear around 10-12k yrs ago as LGM is ending and holocene is beginning; mostly seen in N & S America, some in Europe, little in Africa.
CAUSE: Introduction of New Predator- Humans
-Clovis Tool Kit: Very large blades which are FLUTED(chip in end that would be stuck into poles and used as spears), appear all over America around 12k yrs ago;
-Humans are NON-SELECTIVE PREDATORS, when one prey goes extinct they shift to another
-Animals have not evolved to humans
-Human population size goes up, killing more.
How humans got to new world(2 theories):
1)Oen up of Laurentide/Cordillerian Ice sheet corridor allowing access from Beringia.
-Kill front: Humans come in slowly, easy high protein food form a "kill front" of high population density that must continually expand outward as they kill off prey to find new game.
-Trophic Cascade: Large predators need a lot of prey to support them, so if humans cause extinction of the prey there's not enough food to support the large population; Most prey gone about 10k yrs ago and predators as well.
-Environmental Pressure acting at same time: YOUNGER DRYAS around same time causing a very tramautic event simultaneous of humans; Meteor theorists of Younger Dryas point to the extinction. |
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Term
During the Early Holocen why does the Arctic shoreline indicate sea levels at a number of different positions in last 10,000 years of Holocene?
-EUSTATIC SEA LEVEL CHANGE
-ISOSTATIC SEA LEVEL CHANGE |
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Definition
-Early Holocene still has a lot of ice in Cordillarn and Laurentide making sea level still around 60m below today's.
-Sea level rises from 12-6k due to ice sheet melting; BY 6000 YRS AGO SEA LEVEL LEVELS OFF (NO MORE SHEETS)
-EUSTATIC: Change in world sea level by melting or build up of glacial ice; effects world ocean systems, doesn't explain arctic shoreline, they would have been covered by rising sea level.
-ISOSTATIC: Localized sea level change caused by land surface rising or falling relative to ocean, nothing to do with more or less water in worlds oceans;
-HAS TO DO W/ GLACIATION: Asthenosphere depresses 10-100's of meters with weight of glacier
-Depress directly underneath icesheet but edges rise up. When ice is removed crust slowly rebounds rising up in center and peripheral portions lower back down.
-In case of Arctic shoreline the area was depressed below the ocean even though ocean was lower at the time and has since rebounded rising up at same time as melting ice refilling oceans so its a race up.
-Isostatic rebound in last 6,000 years see 100-120m rise in central portion of laurentide, decreases as you move out peripherally.
-PROCESS HAS NOT STOPPED: still experience isostatic rebound; fastest happened right after ice melted but still correcting like in Fort Prince of Wales built in 1700s on coast of Hudson, gradually becoming farther from water to due to land rising.
***Only isostatic change in S. Hemisphere is in Southern tip of S. America*** |
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Term
Stone age people: Who and when?
-Paleolithic
-Mesolithic
-Neolithic |
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Definition
-Paleolithic: 11-12k yrs ago, stone age hunter and gatherers.
-Mesolithic- 11-9k yrs ago, some domestication & advancement; TRANSITION PERIOD.
-Neolithic: 9-5k yrs agol still using stone-based tech, but evidence of agriculture; not found everywhere. |
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Term
Changes in worlds vegetation in Holocene
-Clemens vs Gleason Forest Stand models
-MARGRET DAVIS? |
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Definition
-Pollen records of 17k yrs ago to modern day: Initially tundra after ice retreat, then spruce/larch, and then modern vegetation around 10k yrs ago; Changes not instantaneous or same in all places.
-Clemens: forest and vegetation communities are like a "Super-organism" that have co-evolved over thousands of years.
Gleason: Suggests "Individualistic species", all species act as individuals not intimately associated w/ one another.
-Margaret Davis: used palynology to test the theories by determining how long the plants have been together to see if all species migrate around together as group or species come in and out w/ climate changes;
-SHE FOUND THAT: Many of the plants in NE America were living along SE America in late pleistocene, migrating to modern limits as recently as 1,000 yrs ago. MOVES VERY SLOWLY, but not all plants have same slow migration rate, each plant has different rate indicating that the modern forests are pretty new and PROVES CLEMENS WRONG.
-Shows that we can expect climate change to break up and form new assemblages of plants/animals. |
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Term
Climate changes of pluvial areas and desert after pleistocene? Sahara? Egypt? Trona Mounds? Monsoons? North regions of hemisphere(Russia)? When did we get to modern world climate?
-Hypsithermal
-Holocene thermal Maximum
-Neo-Glacial climate? New ice age? |
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Definition
-Inter-pluvial areas get drier at end of pleistocene.
-Some areas get wetter; e.g. the "GREEN SAHARA", forming playa lakes from 12-5k yrs ago.
-Lots of archeology of people where no body lives today(Sahara); cave paintings of people hunting giraffe, gazelle, in modern extreme arid regions that do not have those animals.
-Western Desert of Egypt: evidence of playa lake and shoreline found by Macdonald's research. Lithic stone tools found all over former-playa lake areas; also freshwater bones/shells; indicates MUCH WETTER CONDITIONS.
-TRONA MOUNDS: Egyptial lake sediments deposited in playa 10-6k yrs ago that dried up and sediments eroded around leaving big columns of what was once continuous sediment flooring.
-MONSOONS:pulls in warm ocean water vapor in summer cooling over land causing precipitation; during maximum insolation in N. Hemisphere during early/middle holocene, there was more heating in summer and more aggressive monsoon season. As you move past 6k yrs ago, summer insolation is declining rapudly causing less monsoons causing Sahara to DRY UP.
- N. Hemisphere furthest extension of forests northern limits affected by summer insolation, further than today; winter temps don't matter what matters is warmer summer to move tree line north.
-IN SUM:
1)tree line peaks between 9-4l yrs ago then disappear.
2)Monsoons in Africa & Asia peak as pleistocene ends & Holocene begins peaking in max summer insolation and going down since, moved towards modern world around 3,000 years ago(sahara 5-6k yrs ago).
-HYPSITHERMAL: Warmest sea surface temps, max july insolation and ice has disappeared.
-Holocene Thermal Maximum: Warmest point because ice sheets have melted and earths albedo is lower, even though insolation peaked earlier.
-Neo-glacial: last 3,000 years because of their relative coolness, new evidence of mountain glaciers expanding, tree line in russia retreating, expanding tundra, decline in sea surface temps(Caused by decrease in Summer and July Insolation in N. Hemisphere); NEXT ICE AGE 30-50k yrs from now. |
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Term
| What's the iversion model showing? What are the different terms within it? |
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Definition
-Iverson model is a cyclical model of coninuous change in environment.
-During glacil period in terms of vegetation, climate & soil:
1) Cryocratic(glacial) stage= open tundra->steppes; artic mineral soil
2) Protocratic: Open woodland(produces soil high in mineral content; adds organics as vegetation becomes productive), Unleached calcareous soil(has not been removed or weathered- very productive soil)
3) Mesocratic(holocene thermal maximum): mixed deciduous, well developed brown forest soils.
4) Oligocratic/Telocratic: Less summer insolation, older/mature/leached podzol soils(acidic); Some veg driven by temp, some by decreased soil ferility, some maybe human activity- Mostly Heath/Conifer forest.
5) FINALLY cold enough to develop next ice sheet and go back into cryocratic stage; CAN SLIP INTO ICE AGE PRETTY QUICK HOWEVER TAKES TIME TO MELT SHEETS TO BRING BACK INTO FULLY ICE FREE. |
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Term
Humans as an agent of Environmental Change
-difference between last interglacial and today
-Modern humans during holocene |
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Definition
-During last interglacial stage there was no presence of modern humans only hominids w/ stone tools and fire but lacked evidence of artistic development.
-Most humans appear 30-50k yrs ago
-During Holocene
1)humans have spread to most parts of the world.
2)Neandthals disappear just before last glacial maximum leaving humans only hominids.
3) Most of Holocene population was WAY less, upto 1/4 billion; but explodes last hundreds of years. |
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Term
| What is it in the Holocene that allows for rapid population growth? Cultivation vs. Domestication |
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Definition
-Agriculture: original people 18k yrs ago were hunters dependent/limited upon natural pop. of plants/animals, mobile people(Except marine ones).
-1st agriculture when we moved from Pleistocene to holocene.
-Cultivation: Purposely planting, caring, and harvesting a plant or animal.
-Domestication: Selectively breed plant/animal to change genes for certain traits for human benefit. |
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Term
| Areas of first forms of agriculture? Hearths? 1st evidence? Why is it a dynamic period? Down side to sedentary living? |
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Definition
-Near/middle east, agrica, s. america, Meso-america, S. America; called the "WORLDS AGRICULTURAL HEARTHS"
-Agriculture arose in a number of places independently. However it did diffuse to nearby areas.
-Earliest evidence in Fertile Crescent 10,000 years ago cultivating wheat; an so many other varieties of grains/animal. Also evidence of Villages indicate centered prolonged periods of sedentary living.
-Dynamic period because you have people practicing agriculture and stil have people around them practicing hunter/gathering and then you have part-time cultivators.
-Downside to sedentary living is you are stuck and vulnerable; you have a land base and resources that need protection. |
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Term
| What evidence was there of early agriculture in turkey? |
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Definition
-clay pots; storing containers for grains
-Mounds(TELLS) are archeological sites of early settlements of adobe that has since eroded; In "Tells" can find bones and artifacts |
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Term
| Why move from hunter-gathering to agriculture? Pros/Cons of H/G? Benefits of farming instead? |
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Definition
-G/H for small population in good environment food needs will be satisfied.HOWEVER when pop grows or environment degrades, H/G will OUTSTRIP RESOURCES.
-hard to store food
-Susceptible to environment change: Drought, cold, changes in prey migrations.
-Agriculture allows food storage, and trading, provdies longevity of resources, allows for population to increase, become sedentary. |
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Term
| Childes Theory? Correct? Theory revisited? |
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Definition
-Reason for transition to agriculture from hunter gathering is triggered by environment.
-Claims that middle east was a lot cooler and wetter during pleistocene, allowing for an excess of food and game for hunter gatherers. However with the Holocene came warmer and drier, increased desertification/water scarcity. People congregated around water oases and become sedentary. Also, they're in close contact w/ the plants and animals concentrated around the oasis leading to cultivation and eventual domestication.
-FLAWS: 1960s scientists took lake sediment cores and radiocarbon dated them to verify Childes theory instead the climate was completely opposite. Pollen grains showed high levels of CHENOPODS and ARTEMISIA during late pleistocene indicating very arid and cold conditions(Sage brush) & that during the holocene pollens indicate high levels of forest development
-Theory Revisited: Taking into account the Younger Dryas period, perhaps this event caused the environmental situation that forced populations into these oasis pockets (11-13k yrs ago); People looked particularly at fertile crescent to see if Y. Dryas hit the area and polle indicates decrease in tree forest/increase in scrub/grasses suggesting YES there were dry harsher conditions.
-Also: you've got arid/cold conditions in late glacial humans not ready yet, moving towards Holocenes, human populations more successful, large in size, then hit with Younger Dryas arid and unproductive environment forcing people into oasis concentrations right around same time people are starting to cultivate ancestral wheat. |
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Term
| What is the only megfauna animal left in the United states? |
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Definition
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Term
| Other theory besides Childe's for the development of agriculture? Ways of testing? Meso-american comparison to mid-east? |
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Definition
-You have conditions for warm/moist climate for crops, people are growing in population and people just developed agriculture because it was the right sequence of events; couldn't work during MIS 5 because there weren't modern humans yet.
-Tests:Look to see if domestication in other regions occured due to environmental change
1)mes-america: Maize descends from ancestral grass in Mexico, happens later than wheat in mid-east(meaning not associated w/ Younger Dryas), no evidence for environmental change; where wheat domestication occured rapidly, maize was VERY SLOW(5-6k yrs) indicates lots of mixed hunter/gathering; also lack high protein sources of livestock; development of large cities much later(4,000 yrs ago; Mid East was 8-10k); DONT HAVE SAME BASIS FOR AGRICULTURE. |
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Term
| What was the state of agriculture in the world 2000 years ago? |
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Definition
-lots of agriculture worldwide diffused from main hearths, however still large parts such as Australia and Siberia w/ hunter/gathering.
-Evidence of slash & burn agriculture, development of pueblo buildings in mesoamerica.
-Complex stratified agriculture in Europe and Asia.
-Nomadic pasturalism in Africa & central asia
-simplified agriculture in tropics
-OVERALL: Much of temperate regions of world are agricultural, will spread more but by 2000 years ago it was spread all over. |
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Term
| Evidence of diffusion of agriculture from fertile crescent into Europe? Pots vs People Models? |
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Definition
-evidence seen by use of most grains, crops and animals used in Europe originally evolved in mid-east.
-can trace diffusion through clearing of land, domestication of crops, development of sedentary villages gradually up to europe.
-POTS MODEL: Agriculture diffused through ideas, techniques, crps & livestock but people remain the same (diffusion of idea of agriculture but not people)
-PEOPLE MODEL: Where people from fertile crescent move in and displace original populations and instill their agricultural societies.
-DNA EVIDENCE from teeth in early neolithic farmers show evidence of genetic matches found w/ DNA of people from fertile crescent is compelling evidence for PEOPLE MODEL. |
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Term
| Why was diffusion of agriculture so slow from mid-east to Europe? |
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Definition
-no compelling reason to move from hunter to agriculturalist.
-HEavily forested region w/ small growing season trying to clear land for agriculture w/ stone tools
--More evidence of agriculture found in drier, easier to clear lands in south lowlands, but when you push north to central/west Europe there is a shift of 1st agricultural sites on upland which are drier and lighter(Loess) soils because its much easier to cultivate w/ stone tools. |
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Term
| What is the Land Nam Cycle? |
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Definition
-NW Europe pattern where land is cleared where agriculture is 1st established and then land becomes "agriculture in it's very nature" making society become agricultural
-Begin w/ primeval forest(low in ag. plants) -> Move to clearance phase(takes time)which shows 1st evidence of grasses and weeds associated w/ pasturalism(decline in elm/oak, increase in Hazel secondary growth from abandoned pastures)-> Move to farming phase which lasts several generations and then abandon land-> leads to regenerated forests.
-Considered a SWIDDEN AGRICULTURAL STAGE:This system of alternating clearance of forest and a short cultivation period with a long fallow period during which forest returns and soils recover, is generally sustainable as long as the land and population density remains in balance |
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Term
| What was the Avebury Stone hedge? Why important? |
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Definition
-Collinade of massive standing stones that come to round earthern wall, which is neolithic walls of the village of avebury.
-USE OF SNAIL SHELLS: take soil core of avebury LAND NAM CYCLE STAGES; remains of snails transitioning from woodland dominant snails to mixed wood and open ground snails to finally domination of grassland snails. |
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Term
| A Look at the UK: Directly relating History of Land Clearance to Historical events: Pollen analysis show: Original landscape? Landscape of neolithic? Celts? Landscape today? |
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Definition
-Diffusion of agriculture earlist evidence is 5,000 yrs ago and north around 2,000 yrs ago, (not as good land, happened during Roman period)
-Pollen evidence shows domination of woodlands 5,500 years ago; 5-3k yrs ago you have established neolithic farming; 3k yrs ago you have agricultural landscape w/ arrival of Celts; Romans come 2k yrs ago conquer CElts and UK is already a highly agricultural landscape.
-TODAY: massive reforestation in UK, more than has been in last several 1000 years ago; do not need to clear as much land(import more) and increase in hunt & game, etc. |
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Term
| Diffusion of Polynesians and effect on landscapes. What were their names? When did they expand? What did they have with them? What happened on New Zealand? The classic and real story? |
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Definition
-No people before polynesians in Hawaii, Easter Islands, etc.
-LAPITA PEOPLE seen through their pottery, expansion of S. pacific from Asia(3800-3200P)
-2100 years ago- arrival of polynesians to S. Pacific in outrigger canoes; Brought with them: animals(pig), rats trees (coconut), breadfruit & crops.
-NEW ZEALAND: Largest island, occupied last 1000 years, MASSIVE IMPACT ON LANDSCAPE w/ arrival seen through pollen reocrds.
-NZ used to be heavily forested w/ palms(NOTHOPAGUS)
-Arrival of Polynesians indicate rapid disappearance in forests, increase in grasslands; Polynesians already had agricultural tool set with them, land clearing techniques, fire, plant/animal species so it was a much more rapid process then other diffusions.
-BRACKEN pollen seen in disturbed areas following fire was very present.
-extinction of the Mao; bird megafaun
-Classic story: Polynesians come in cut down palms for farming, and quarrying of statues; REAL STORY- Lots of remains of palm seed that are chewed on by rats indicating that accidental introduction of them caused a massive hit to the palm regeneration as the rats ate all their seeds and expanded in population of this monoculture while at the same time polynesians were putting pressure on the landscape. |
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Term
| Case of Hawaii: What was unique? Fire? |
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Definition
-Hawaii didn't have all lowlands cleared and agriculture everywhere which was idea of most Polynesian colonies.
-FIRE: lake cores indicate some natural fires but much more rampant during polynesian colonization as seen in the charcoal sediment.
-Pollen indicates a lot of variation in open/forested vegetation(dynamic landscape) during polynesian times.
-MOST CLEARANCE OCCURED DURING EUROPEAN PERIOD. |
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Term
| North Coast of Africa/Mediterranean: What it looks like today? What does evidence indicate of what it used to be in the past?Whats the Beysehir Occupation? And what caused the change? |
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Definition
-Modern day shrubby/arid palnt cover, very little soil cover in uplands, deep amounts washed off into low lying areas; Spectacular roman ruins, indications of lots of agriculture and cities. VERY LITTLE AG. TODAY
-from 3000-500 AD, period of intense agricultural development; Huge focus on ARBOR agriculture- trees, grapevines, walnuts, ORCHARDS.
-Beysehir occupation: roman/greek city, focus on olive/graps, high population, caused by trade & period of stability; MASSIVE deforestation and expansion of the Beysehir occupation areas (Arbor ag).
-Reason for collapse- Not because of deforestation/soil erosion; Romans and greeks built massive strcutres for irrigation and prevent soil erosion. What happened was roman empire collapsed, Byzantine takes over, very unstable, trad link breaks off, inability to support agricultural infrastructure, eventually they gave out and erosion of soils peaked at collapse of greek/roman system. |
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Term
| The Mayan study: Soil today? Water techniques? What evidence indicates a collapse of the Mayans and when? Reasons for collapse? |
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Definition
-millions of people, densely settled required huge amounts of agriculture; when you walk around today it's thin soil, most of it piled up in valleys.
-Very dry, sophisticated water techniques: big sink holes underground, or swamps, reservoirs.
-Massive collapse of Mayas 1100 years ago; signs of warfare, hasy fortifications, evidence of slaughter/death of ruling class, HUGE population decline.
-Massive land clearance & agriculture suggest complate agrarian landscape and then abandoned to jungle, Why?
1) Population so high, too much stress on land, caused collapse from overdemand of resources, loss of soil, smaller in total population size. Additionally it was an Early stages of city-states, unstable stratified social structure(few rule the masses), toppled by unsustainable social structure
2) Dramatic climate change lead to end of mayan civilization
-additional thoughts: sressed for water, shift to drier conditons during mayan collapse as seen through gypsum(carbonate) deposits indicating a saline environment. Also increases in sulfur and O18(heavy, means high evap rates). Was THIS the sole cause or just a contribution? |
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Term
| Greenland: Who inhabited it? What for? When did the Norse get there(what climate period & dates)? When/how did they die off? (Climate period & dates) |
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Definition
-Inhabited by Innuate and Eskimo but also signs of European villages, cemetaries and churches of Norse/Viking settlements.
-Found during exploration or fishing and used as a trade spot for wool, tools, food w/ Scandanavia
-The Norse: 800AD massive expansion eastward into France, Britain, Normandy & Russia.
-860-870AD: Setled Iceland as seen w/ Land Nam Cycle in these areas.
-985-1000AD: Norse spread west, establishing settlemtns(Eric the Red, Leif Erickson) in Greenland; Began croping crops, pastures for sheep & cattle. Lots of fishing; Trade w/ iceland, Norway, Denmark; Had walrus skin/tusks.
-1000AD expansion to North Coast of N. America-> New Foundland(short occupation); there's evidence of them sailing south in journals, depicting wild grapes(New England) but no evidence of settling.
-Dying off: Began in 1341(west), 1380(middle) and finally 1500(East-largest) died out in which you stop seeing records of annual trade boats; When Danes resettled in 1800s to make sure the norse were still christians there was none left.
-What killed them: Original expansin in 800 AD climate was warm; From 800 to 1300 it was considered "Medieval Warming Period" which had less atlantic storms, ice free Greenland. Also see European villages/farms in higher altitudes.
-From 1300-1850 You have the Little Ice Age; colder conditions, glaciers rexpanding beginning in 1300, adabonment of high elevation farms,scandanavian harbors choked w/ ice, Temmese river in England frozen over, Rocky Mtns show signs of glacial advances through till and moraine and by 1850 conditions began to warm again. However in that time period it may have become too hard for norse to supply food for cattle, shorter walrus hunting season and harder trade routes w/ Norway. Did norse abandon or get stuck?(No wood for shipbuilding) |
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Term
| Medieval Warming Period and Little Ice age: When did they occur and why? |
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Definition
-Medieval warming: 800-1300 AD Because:
1)during this time through sheer luck there was less than average volcanic activity globally usually puts sulfur dioxide into the atmosphere dimming it and making it less transparent for light to enter. We know this through ice cores, when theres volcanic activity sulfur dioxide gets deposited in ice, it's highly conductive to electricity(good form of testing).
2) At the same time there was high sun intensity/activity which changes the amount of UV radiation earth recieves. This is documented in chinese documents of sun spots.
-Both of these reasons are reversed during Little Ice Age; In Sum these perturbations of Warming and Little Ice Age are caused by a combination of volcanic and solar activity. It doesn't take much to change the temp of earth. |
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Term
| What are greenhouse gases and how much of an effect do they have on the climate? How much is natural and how much is human added? how do we calculate amount? WHAT WE KNOW: main sources of CO2, original CO2(How?)? human activity effecting CO2? when did it start? How much has it changed the force of Earth's Radiative Balance? |
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Definition
-Greenhouse effect: Lots of energy coming from sun to earth in form of light, passe through transparent atmosphere and hits earths surface reflecting back out or reradiating into heat which now becomes intercepted by atmosphere keeping surface of planet warm. Keeps earth inhabitable, however by adding extra greenhouse gases we absorb more heart.
-Climate is naturally variable as seen by Little Ice Age and Warming Medieval period; The 20th century was as warm as medieval warm period, 21st is warmer
How much is caused by CO2 that we've added?
-Natural amount: 280 ppm, going down to 200ppm in ice age; Today we are at 400ppm, completely unnatural amount.
-Prior to 1950's no way of testing for CO2, too small of an amount; 1958 UCSC profressor figured out technique, set up station on Mauna Lao, Hawaii because its far from local sources of CO2, always measurement of BASELINE CO2 in atmosphere.
WE KNOW:
-CO2 from human sources in 3 main ways: 1)Burning fossil fuels releases ancient CO2
2)Land clearance removes CO2 sequestrating plants and release from soil.
3) Methane produced by human landfills broken down in anaerobic conditions, rice cultivation and flatulence by cattle.
-We know pre-industrial revolution was down to 280 ppm of CO2 through Ice cores that have trapped bubbles of atmosphere up to 650,000 yrs ago(Antarctica) and 150,000(Greenland); compare the CO2 measurement from ice core w/ Mauna loa and determined a safe representation
-Now we're at 400ppm, more than last 650,000 years(Completely off the charts); no doubt of human activity as an influence; started in 1800's.
-It will change force of Earth's Radiative balance: additional heating from methane- 0.4 watts per meter sq.; from CO2- 1.25 watts per meter sq |
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Term
| Is human activity and release of greenhouse gases enough to change the climate? And how has and will it effect us? Why should we care? |
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Definition
-Only 0.5 degree celsius increase in temperature; 1.25 watts per meter sq(CO2) and 0.4 watts per meter sq(methane) increase in Earth's radiative force; VERY SMALL AMT
-Concensus is YES, but if it's the only force is DEBATABLE:
1)only 0.5 degree increae form 1850 to today but takes a lot of energy to heat entire earth
2)Tiny increase in global sea leve(100-150 millimeters)
3) Snow cover decrease in N. Hemisphere
-All at same time of increasing greenhouse gases...
-Event Scientist Mueler of UC Berkeley, strong opponent of climate change found that the climate is warming.
-ICC estimates 3-4 degree celsius increase from now till end of century, greatest in high latitudes(up to 7 degrees).
-The natural component: Solar variability increases parallel to 20th century warming! ALSO fairly low volcanic activity! BUT we couldn't see super high temperatures like we do without influence of greenhouse gases. THUS it's a combination of both natural and humans; If natural variability changes it will make the climate change more moderate or more extreme.
-CA: Water shortage in the South and sea level rise in the bay area; 16 inches will drown parts of SF including airport(expected by 2050-70) |
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