What Is Ozone? Why Should We Care about Something We Can’t See? Dr. Michael J Passow Earth2Class Introduction 19 Oct 2013

What is Ozone? Simply explained, ozone is a highly reactive form of oxygen molecules O 3 Ozone poses two biological problems, depending on whether it is: “Tropospheric Ozone” or “Stratospheric Ozone”

Tropospheric Ozone Produced mainly by reaction of sunlight, oxygen, and exhaust from combustion engines (hydrocarbons/nitrogen oxides) Major component of photochemical smog Dangerous to people with respiratory ailments Also damages plants, especially in North American and European forests

Stratospheric Ozone Above 11 km (7 mi) “Ozone Shield” protects against solar ultraviolet radiation Satellites have monitored significant declines over past few decades Most noticeable declines over Antarctica “Peaked” (?) in 2006

Measured in DOBSON UNITS Number of O 3 molecules in a vertical column of the atmosphere

Progress in Monitoring 1979 – 1993: NASA/NOAA Nimbus – 1994: Metor-3 (USSR) 1996 – 2004: NASA Earth Probe TOMS 2004 – present: OMI instrument aboard Aura (KNMI/NASA)

NASA Ozone Monitoring NIMBUS-7 TOMS INSTRUMENT AND SATELLITE INFORMATION Other satellites and platforms (balloon sondes)

Nimbus 7 Satellite

Ozone Hole Watch NASA provides info about O 3 maps, meteorology, facts, multimedia, and education ozonewatch.gsfc.nasa.gov /

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2013 Season

What Probably Created the Ozone Hole? Chlorofluorocarbons (CFCs) Synthetic hydrocarbons in which H is replaced by halogens (e.g., CHF 2 Cl, CFCl 3, CF 2 Cl 2 ) Also, Br compounds Widely used refrigerants and propellants In the atmosphere, may take 60 – 100 years to decompose 1987 Montreal Protocol established scheduled reduction in use

What Else Depletes Ozone? Nitrous Oxide (N 2 O) Like CFCs, stable in stratosphere and able to deplete O 3 Unlike CFCs, 60% derived from natural sources >decomposition of N compounds in soil and water >burning fossil fuels & plants (deforestation) >use of manure, fertilizers on crops

Some Dangers of N 2 O Montreal Protocol does not regulate N 2 O In troposphere, potent greenhouse gas (~300 x as potent as CO 2 ) Impact on ozone hole not definitively established, but of concern to scientists

Ozone Hole History :// htm :// htm

NOAA’s Ozone Page

References /Ozone.html _hole_large.jpg