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
IPCC findings
REPORTS IN 1990, 1995, 2001, 2007, and 2013
-the 2013 report stated if CO2 ppm is doubles there will be a likely increase of 2-4.5 C
—an increase of <1.5 c is very unlikely
—the IPCC defines likely as 66-90% probability and VERY unlikely is 1-10% probability
2018 report focuses on limiting warming to 1.5 C
—were already seeing the affects of 1 C through more extreme rather, rising sea levels, and diminishing arctic sea ice, among other changes
Role of trace gasses
Methane (CH4) nitrous oxide (N2O) chlorofluorocarbons (CFCS) and ozone (O3) all absorb wavelengths of outgoing radiation from earth
Methane as a trace gas
Produced by anaerobic (don’t like air) bacteria in swamps, wetlands, and animal waste
- 20 s’more effective at absorbing infrared radiation
- .4% per year growth
Nitrous oxide (N2O)
Laughing gas mostly from agricultural activity but also from fossil fuels combusting
-.2% per year growth
CFCS-chlorofluorocarbons
Manufactured chemicals -man made
- industrial propellants and coolants
- very stable and long lived
- 5% per year growth
Ozone O3
Tropospheric zone
- lightening, automobiles ignitions, and other photochemical reactions
- .5% per year growth
Aresols
Tiny, liquid and solid particles that are suspended in the air
-natural sources include wildfires, dust storms, breaking waves, and volcanoes
-human generated aerosols come fro the combustion of fossil fuels and burning vegetation
—black carbon is spot generated by combustion process
Absorbs incoming radiation
Possible effects of these changes in trace gasses and ozone on temperature
Because the climate system is so complex’ predicting specific regional changes related to increased levels of CO2 is speculative
- magnitude of temperature increase is not globally uniform
- precipitation changes will also vary across the globe
Possible affects on sea level rise
Sea level has risen 25 centuries since 1970
-will affect low-lying countries and regions with a gently sloping shoreline
—Atlantic coast of the us
What is sea level rise driven by
Melting glaciers
Thermal expansion
-if all the glaciers and ice sheets melted sea level would rise 23 feet
The changing artic as a possible affect of global warming
Amount of sea ice in artic has declined by 13% since 1979
-Greenland and Antarctica ice sheets have dropped an average of 475 gigatons/year
(1 gigaton=1 billion metric tons)
Permafrost (frozen ground)
Thawing permafrost is a positive feedback mechanism
-organic material stores in the permafrost will start to decay and release carbon dioxide and methane
Possible effects of global warming on increasing ocean acidity
When atmospheric carbon dioxide dissolves in seawater, the oceans become acidic
-makes it harder for calcite-secreting marine organisms to grow hard parts
The potential for surprises with global warming
Due to complexity of earths climate system, we might experience relatively sudden, unexpected changes or see some aspects of climate shift in an unexpected manner
—a constant state of change is very likely
Climate feedbacks
Feedback - in indirect or secondary change either positive or negative that occurs within the climate syste in response to a forcing mechanism
Positive: self feeding/sustaining feedback that further enhances the impacts of the climate forcing
Negative: a feedback that pushes the climate system back towards the initial state
Important climate feedbacks
- Oceanic warming-positive
- warm water can hold less carbon dioxide than cold water so more carbon dioxide released - Ice cover/albedo feedback-positive
- increase temperatures leads to decreased ice cover, which drops the albedo and causes temperatures to increase further - Cloud atmospheric vapor feedbacks
- higher temp leads to higher evaporation and higher atmospheric vapor content
- high thin clouds have very low albedo, but trap outgoing radiation(greenhouse gas)-positive
- low think clouds (cumulus) have very high albedo reflecting radiation back to space - positive - Methane clathrate and frozen soils-positive feedback
- increases surface temperatures are leading to the thawing of frozen soils (permafrost)
- this allows organic matter to become oxidized in soils and to the release of methane
Coast
Oceans moderate climate and whee society meets the ocean
Major oceans
Pacific Atlantic Indian Arctic Southern
What is the significance of the coasts
Ocean covers 70.8%
Regulates climate
60% of humans live near the coast
Under sea landscape
The current configuration of tectonic plates
- most continental crust is in northern hemisphere
- most oceanic crusts in the Southern Hemisphere
Bathymetry
Describes to topography (elevation) of ocean Bain’s
- continental shelf: shallow gentle slope (.3d)
- continental slope: descends from 500 m to 4 km at 2 d
- continental rise: transition zone from 4 to 4.5 km
- abyssal plain: flat, low relief bottom below 4.5 km