Ozone Depletion
• Stratospheric ozone• UV light• Chemical processes• Environmental effects• Solutions
Atmosphere
• Stratospheric ozone• 20-30 km altitude• 19 mi at equator, 9 mi at the poles• 400 ppb
Ozone shield
• 99% of all UV is absorbed (UVC and most UVB)
• UVA is not affected by ozone
Production of ozone
Measurement of Ozone
• Dobson units: 1 ppb ozone
• Survey began in 1957 over the Antarctic
• Taken in October, springtime
• 1957-1970: 300 DU• 150 DU by 1986
Ozone and CFC’s• Molina and Rowland in
1974• CFC’s are stable• Long residence in lower
atmosphere• UV radiation breaks down
CFC and releases Cl• Cl reacts with O3
• Increase UVB at the surface
Formation and destruction of ozone
Emissions
Usage2003
Ozone Hole
Polar Stratospheric clouds
• Polar winter formation• Have polar vortex• Isolated air mass• Nitrogen oxides held
in clouds as nitric acid• NO3 particles grow
and fall out• Facilitates ozone
depleting reactions
Polar vortex
In Springtime, sunlightReturnsNo nitrate to form CloNO2
Environmental effects• UV damage to DNA• Skin cancer• Cataracts• Suppression of immune
system• Ecosystem:• Primary producers• Food chains• Development in aquatic
larva
Managing ozone depletion• Montreal protocol, Sept
1987– Production of CFC elimination
• Economic gap• Replacements: HFC and
HCFC• Shorter lifetime, less
reactive• Collection and reuse (no
venting)• Expensive replacements
Climate Change• Climate Swings• Greenhouse gases• Evidence• Predictions• Control
Historic Climate shifts
• Milankovitch cycles: shifts in earth‘s orbit and tilt• Volcanic activity: Mt. Toba
El Nino/Southern Oscillation• Trade winds keep warm water
in W. Pacific. La Nina• El Nino: Shift in tropical
depression• Northern Jet stream splits
changes rainfall patterns• Pacific decadal oscillation:
warm water in northern pacific moves back and forth.
• Cool water in north help Alsaka salmon runs, warm off coast and then switches.
Human Activities
• Industrialization• CO2 increased 31%, CH4 inc 151%, N2O inc 17% over
since pre-industrial times.• 40% of excess CO2 absorbed by oceans• Methane a big problem
Evidence of Climate Change• Avg global temperature has climbed 0.6oC over last century• Arctic sea ice is 40% thinner, Antarctic glaciers are retreating 50m/yr.• Alpine glaciers are retreating• Ocean acidification• Sea level has risen• Changes in animal behavior, breeding cycles• Storm frequency and intensity are increasing
Larsen B ice shelf-- Antarctica
ConsequencesArctic sea ice Alpine glaciers
PredictionsPredicted warming with doubling ofCO2
Sugar maple range
Controls
Reduction of Carbon Emissions
• Burn less fossil fuel: Turn down your thermostat
• Plant Trees for shade and CO2 uptake• Insulate your house• Replace old appliances• Use compact fluorescence light bulbs• Use renewable energy