O3zone StoryTerry Deshler, Atmospheric ScienceFormationimportanceLosspre 1974pre 1985pre 2010recoveryWhats new Relationship to global warmingThe end

Relationship to Global Warming PeripheralOzone has a slight greenhouse effect, butLoss of ozone over Antarctica may have intensified the polar vortex and reduced the warming expected in AntarcticaCFCs are a significant green house gasReduction of CFCs largest single human action mitigating the current warming

The End?No, we have to limit the release of CFCs into the atmosphere from now on.The good news - the atmosphere will cleanse itself of present atmospheric chlorine.The bad news - it will take another 50 years to see the ozone hole above Antarctica disappear.

Ozone FormationO2 + h O + O

Then, O + O + M O2 + MorO + O2 + M O3 + M (Ozone created) Where will this primarily occur?Also, O3 + h ( > 310 nm) O2 + Oand O3 + h ( < 310 nm) O2* + O* (UV absorption)

O2* + O2 2O2 + thermal energy (Excess energy dumped O2* O2 + h ( = 1.3 m) in ozone layer)

Importance of ozoneAbsorbs DNA damaging UV radiationThis UV affects both animals and plantsSH/NH differences - In summer UV radiation is 50% more intense in SH than NH. Australia - world leader in skin cancerReasons 10% - Earth is closer to sun in SH summer than NH summer20% - Antarctic ozone loss/clearer atmosphere20% - Unknown

Food Preservation100 BC - 1700s, Early methods: Drying, Salting, Cool cellars/Spring houses, Pickling, Fermenting, Canning.Cooking -> could eat spoiled food - spices to hide the flavor.

1803 Ice Boxes - Thomas Moore invented the insulated box, with ice was in a separate container above the food storage area. Relied on stores of natural ice from frozen lakes and rivers.

1850s - Methods to artificially produce ice were developed.

1890 - Warm weather/rain lead to a shortage of natural ice. Spurred the development of mechanical refrigeration.

Refrigeration

1918 - Kelvinator, First refrigerator introduced to American market.

1920s - Refrigerators used ammonia (NH4), sulfur dioxide (SO2), (toxic, odorous), and methyl chloride (CH3Cl), (toxic, no odor) - silent killer.

1928 - Thomas Midgley, Fridgidaire, dichlorodifluoromethane (CCl2F2)

1929 - Fridgidaire and DuPont joined to produce CCl2F2, and CFCl3 as Freon.

CFCs1928 - First totally safe molecule for mechanical refridgerators - Thomas Midgley, dichlorodifluoromethane (CCl2F2), Fridgidaire and DuPont joined to produce CCl2F2, and CCl3F as Freon (F12, F11).

1941 - Automobile air conditioning - Packard

1943 - Bug bomb used in WWII CFCs became propellants for aerosol spray cans.

1940 - 1960 - Uses of Freon boomed.

1970s - CFC production 600,000 tons annually growing 10% per year. Uses with immediate releases to the atmosphere - 66%, refrigeration - 20%

1971 - Lovelock - Electron Capture Device coupled with Gas Chromatography -> First capability to detect molecule concentrations on the order of ppt (parts per trillion = 10-12).

1974 - Molina and Rowland - simple question - What happens to CFCs released into the atmosphere? (awarded Nobel prize Chemistry 1995)

CCl3 F (F-11) + h ( < 240 nm, z > O3 layer) CCl2F + ClCCl2F2 (F-12) + h ( < 240 nm, z > O3 layer) CClF2 + Cl

Then Cl + O3 ClO + O2 ClO + OCl + O2Net: O3 + O O2 + O2

This would occur above ozone layer altitudes above 30 km

Reservoir molecules1975 - 1980 Predicted ozone losses above 30 km were not observed. Reservoir molecules discovered. Cl + CH4HCl + CH3ClO + NO2ClONO2HCl and ClONO2 are reservoir species.

1984 Models predict 10% ozone loss in 100 years for current CFC production rates.

Ozone Profiles McMurdo Station, Antarctica1986 - 1994199419861987198819891990199119921993

Ozone ProfilesMcMurdo Station, Antarctica

1995 - 2000199619971998199920001995199519961997199819992000

Late winterspringDuring Winter

Catalytic Cycle Polar Stratosphere PSC particle + HCl + ClONO2 Cl2 Cl2 + h Cl + Cl 2 [ Cl + O3ClO + O] ClO + ClO + M ClOOCl + M (M=N2 or O2) ClOOCl + hCl + ClOO ClOO + MCl + O2 + Mh = Suns returnNet2O3 + h3O2A single Cl atom can destroy more than100,000 ozone molecules.This cycle will continue until the NO2 and OH lost in the form of HNO3 in polar stratospheric clouds is replenished by mid latitude air, thus converting Cl back to its reservoir species.

Nitric acid/waterIceNitric acid/waterIce

Molina &Rowland,1974ReservoirMoleculesDiscoveredMontrealProtocol, andamendmentsAntarctic ozone holediscovered

RefrigerantsFoam ExpansionSolventsPropellantsFire Extinguishants1974Ozone DepletionHypothesis1986Base Year forMontreal Protocol1996CFC PhaseoutComplete inDeveloped CountriesCFCsHCFCsHFCsRefrigerantsOtherThousands of tonnesAn Industry in Transition

Return

What do 22 years of ozone measurementsat McMurdo indicate?

Ozone history compared to PSC volume (alias temperature) 1986 2008. Stephanie Luberda

4 K5 KICE notshownNitric acidhydrateNitric acid Solution dropStratospheric aerosol volumes

Ozone Instruments (Laboratoire Meteorologique Dynamic & U. Colorado)Particle Instruments (U. Wyoming)Flight control (CNES)

Measurements continue at McMurdo:To maintain good records in anticipation of ozone recovery. To test quantitative models of ozone loss.

This last aspect is focus of current measurements.

McMurdo Antarctica78S - 1989

PostscriptThe ozone loss story is a positive oneA global problem created by local human activities was identified, and reasonable solutions adopted by the worlds leading countries to reduce and eventually eliminate the problem.Is there a relation to global warming? Physically - minimal. Politically - the actions on ozone loss may serve as a model to direct future decisions by world leaders

TroposphericChlorine

The fluorochemicals industry (producers and users) began a significant transition in 1994; the transition intensified in 1989 when the phaseout of ozone depleting substances under the Montreal Protocol began. The transition caused a selection process where remaining uses of fluorochemicals are those with the highest societal value. Other uses now employ other fluids or technologies. The transition has caused significant disruption and investment costs within the industry. The transition has been accomplished without any significant disruptions of services to consumers. Most of the remaining fluorochemicals amounts are used as refrigerants or expansion agents for insulating foams. Other uses include high value fire extinguisants, solvents and propellants for medical devices. The transition to date has been driven by concerns over ozone depletion. CFCs (halons have been included in this category for display purposes) and HCFCs are ozone depleting compounds. HFCs do not deplete ozone. Now the focus is on climate change and the question is how can the atmospheric emissions, and hence, climate effects of HFCs be limited.