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