Final Flashcards
Climate system
Multidimensional system of mainly interacting parts Including: Atmosphere Hydrosphere Geospnere Biosphere Cryosphere (ice and snow(
How is climate change tracked
- Historical records only go back a couple of centuries (good for 1000 years)
- Recorded in glacial ice
- Tree rings archives of environmental history
Historical records for climate change
Reconstruction;of past climate change i the field of paleoclimatology
-scientists use proxy data (indirect evidence of climate change
Proxy records - climate change recorded in glacial ice
Some ice cores represent over 200,000 years of climate history
- oxygen isotope analysis
- carbon dioxide and methane (air bubbles trapped in ice)
Tree rings- archives of environmental history
Growth rings added each year
-thickness and density of rings reflect environmental conditions
Tree things not tied to local trees called floating chronologies
Dendrichronology
Study of tree rings
O2 isotopes and ice volume
Isotopes are atoms of an element that have varying number of neutrons
Proxy records - deep sea sediments
-variety of proxies in sediments
—foraminifera (singe felled organisms)
—pollen
—organic and inorganic compounds
Deep sea sediments foraminifera
Disturbance of, changing abundance, and extinction of species describe environment
Guemnerlitria
Increases during environmental stress
Deep se sediments also lake sediments pollen records
Distribution changes in abundance etc tell us about changing environments
Climate forcing mechanisms
Any process capable of altering the global balance, capable of affecting climate
Can be: internal process-occur within the climate system such as oceanic current circulation
External processes-occur from without and ca be natural or anthropogenic
—time scales can vary wildly from years to millions of years
Important easternal forcing mechanisms
1. Plate tetctonics Milankovitch cycles (orbital variations) Atmospheric chemistry Volcanism Solar activity
Plate tectonics as an external facing mechanism
The earths surface consists of a variety of large and smaller tectonics plates
-super continents have existed several times and have broken apart
Plate tectonics impacts:
Changing oceanic currents (poleward heat advection)
Land surface area near the equator, near the pols (latitudinal radiation balances)
Mountain ranges (atmospheric circulation, silicate weaterhing) and more
Closing of the Central American isthmus
-more moisture carried to high latitudes=more freshwater for sea ice and more snow for glaciers to build
Milankovich cycles (orbital variations)
Driving force behind gladiator cycles
Orbital variations
-eccentricity-changes in orbital shale (100,000 year cycle)
Tilt-(or obliquity) tilt varies between 22.1 and 24.5 degrees (41,000 cycle)
—today 23.5 degrees
-precession-(26000 year cycle) also called wobble
—axis points to different spots in the sky during a cycle of about 26,000 years
Atmospheric chemistry as an external mechanism
Greenhouse gas concentrations
—more greenhouse gasses=trapping more long ave radiation=higher temps
—from volcanoes too
Volcanism as an external forcing mechanism
Volcanic eruptions release aresols (high albedo, reflects more shortwave radiation) which can cool earth
Mount St. Helens, 1980-cooling less than .1C
El chichón, 1982- cooling around .3 to .5 celvius
Mount pinatubo, 1991 cooling around .5 c
Solar activity as a;external forcing mechanism
Suns output is not constant
-varies according to sunspot numbers
—sunspots are darkened spots on the sun with temps 400 to 1800 c lower than areas around the spot
-increased solar output is due to faculae which are very bright spots near the sunspot
—11 year cycle
Medieval war:period and little ice age
Due to less sunspots means colder which accounted for the little ice age
Human climate impacts
Humans have been modifying the environment for thousands of years
-ground cover has been altered by fire and overgrazing
—results in modifications of reflexivity, evaporation rates, and surface winds
-rising CO2 levels: carbon dioxide in greenhouse gas
—let’s show wavelength solar radiation
Ass through the earth but traps long wavelength earth radiation from passing back into space
Rising co2 levels
Humans add carbon dioxide to the atmosphere through burning fossil fuels and deforestation
—CO2 Levels are the highest in the past 600,000 years
Response to more co2
Global temperatures have increased in response to increases atmospheric carbon dioxide
-global temperatures have increases .8 C in the past century
—the warmest 16 years (since 1850) have occurred since 1995
But we do need them!! Without greenhouse gasses the earth would be about 33 C cooler on average and we couldn’t live if it was this cold
Expectations for future of with co2
Temperatures are expected to continue to increase in the future
-amount of increase depends on amount of emitted greenhouse gases
IPCC
Intergovernmental panel on climate change formed in 1988 under control of the UN