Global Warming and the Greenhouse effect

• causes natural and anthropocentric ( human caused ) 
• the atmosphere is the gaseous envelope that surrounds the earth
• atmosphere composition 
• dust 
• major gasses : N (78%) and O (21%) 
• Minor gases: Ar (0.93%), CO2, CH$, etc. 
• ozone (O3) 
• water vapor  
• increase in "greenhouse" gases, which in turn traps heat 
• more greenhouse gases = more warming 
• greenhouse gases are: carbon dioxide (co2), nitrous oxide ( n2o), methane (ch4), cfc's water vapor ( clouds) 
• anthropogenic enhancement 
• industrialization and consumerism; burning of fossil fuels 
• greenhouse gasses in the Earth's atmosphere absorb thermal energy ( infra-red) radiated from Earth's surface
• how it works 
• co2 occurs naturally in low concentrations but has a big effect 
• how co2 is added to the atmosphere 
• exchange between atmosphere and seawater 
• biological respiration 
• burning of fossil fuels 
• volcanism (volcanoes ie mammoth mountain)  
• fires ( burning tress) 
• how co2 is removed form atmosphere 
• exchange between atmosphere and seawater 
• photosynthesis 
• formation of carbonate rocks ( limestone) in oceans 
• fossil fuels and fires are instantaneous greenhouse gasses 
• consequences of climate warming 
• glaciers/ sea ice 
• sea level 
• species migration 
• catastrophic weather events 
• shut-down of the ocean conveyor belt ( worst possible thing to happen) 
•  what factors effect sea level 
• increase in glaciers = fall in sea level 
• less glaciers - rise in sea level 
• slower seafloor spreading - drop in sea level 
• faster spreading - rise in sea level 
• ocean cools, water contracts - drop in sea level 
• warming oceans - rise in sea level 

Orbital Eccentricity

The shape of the Earth's orbit ( viewed from above)
Cycles every 400,000 and 100,000 years

• Is it more circular-shaped or more egg- shaped? 
• circular: low eccentricity 
• oval shaped: HIGH ECCENTRICITY 
• obliquity or axial tilt 
• changes from 21 degrees to 24.5 degrees 
• cycles every 41000 years 
• greater tilt, the greater the seasonality 
• minimum tilt develops more glaciers 
• maximum tilt : warmer summers near poles and less glaciation 
• orbital procession 
• earth wobbles like a spinning top 
• the spin axis sweeps out an imaginary cone 
• cycles every 19-23 thousand years 
• how do orbital changes show up in the geological record? 
• example: changes in tilt 
• More tilt = more severe the season 
• less tilt = less severe of the season 
• effects 
• slightly warmer winters 
• but cooler summer 
• snow from winter doesn't melt 
• past glaciation interpreted extended of ice sheets 20,000 years ago 
• interpretation temperature variations over the last 100,000 years 
• milankovitch cycles with paleoclimate records for the pas million years 
• periods of low eccentricity and glacial periods 
• showed that procession along with eccentricity and tilt, affects the total amount of insolation 
• insolation = exposure to suns rays 
• lighter composition absorbs lighter isotopes 
• correlation in inferred temperature an co2 concentration