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Antarctic Climate Change and Stratospheric Ozone Depletion. Karen L. Smith Lamont-Doherty Earth Observatory Earth 2 Class October 19, 2013. Antarctic Climate Change. Antarctic climate change over the past several decades has been dominated by the effects of stratospheric ozone depletion.

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Antarctic Climate Change and Stratospheric Ozone Depletion


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    1. Antarctic Climate Change and Stratospheric Ozone Depletion Karen L. Smith Lamont-Doherty Earth Observatory Earth 2 Class October 19, 2013

    2. Antarctic Climate Change • Antarctic climate change over the past several decades has been dominated by the effects of stratospheric ozone depletion Thompson et al. 2011

    3. The Antarctic Ozone Hole (2012) Movie courtesy of NASA: from the OMI instrument on board the AURA satellite

    4. Outline • Introduction to Ozone • Ozone Depletion • The Montreal Protocol • ODP vs. GWP • Ozone and Climate • The “World Avoided” • Antarctic Sea Ice and Ozone UNEP, The Ozone Story, 1998

    5. Introduction to Ozone

    6. Ozone (O3) • Blue colored, strong smelling molecule • Absorbs UV radiation • Unstable: constantly breaks down, reforms in stratosphere • Breakdown can be accelerated by certain chemicals (catalysts) • Also a primary constituent of photochemical smog in the troposphere

    7. Atmospheric Pressure Altitude (km) 50 Stratosphere 40 Felix Baumgartner Weather Balloons 36 32 U2 Spy Plane 28 24 20 16 Stealth Bomber Commercial Airliners Troposphere 12 Mt. Everest 8 4 Denver 0 0 0.2 0.4 0.6 0.8 1.0 Atmospheric Pressure (atm)

    8. Thermal Structure of the Atmosphere

    9. Ozone in the Atmosphere

    10. Ozone Formation in the Atmosphere • Solar radiation striking the Earth’s atmosphere is absorbed by air molecules • O2 strongly absorbs in the UV band • Absorption of UV by molecular oxygen splits the O=O bond, forming O free radicals • These O free radicals combine with molecular oxygen to form O3 (ozone)

    11. Ozone Absorption in the UV Band • UV radiation includes wavelengths from 200 to 400 nm • UV-A 320-400 nm • UV-B 200-320 nm • UV-C 200-290 nm • UV-C • Nearly all UV-C is absorbed in the upper atmosphere • UV-B • 90% of UV-B is absorbed by the atmosphere, mostly by O3 • UV-A • Not strongly absorbed by the atmosphere

    12. Anthropogenic Ozone Depletion

    13. CFC’s (1928) – Wonder Gas! UNEP, The Ozone Story, 1998

    14. CFC’s (1928) – Wonder Gas! UNEP, The Ozone Story, 1998

    15. Stratospheric Ozone Depletion • Results from large-scale industrial manufacture and release of synthetic compounds (chlorofluorocarbons, CFCs) in quantities that can interfere with chemical processes in the Earth’s atmosphere • Unanticipated sideeffects of CFCs – like acid rain, global warming, etc., were not expected… only appreciated in hindsight • Environmental “success” story?

    16. Polar Ozone Destruction • “Ozone Hole”:term for regional, seasonal thinning of O3 layer over the poles • Cause: catalytic destruction of O3 by Cl and Br • Mechanisms are complex: • Ice clouds form in frigid stratospheric winter air, absorb HNO3, ClONO2, HCl • Surface reactions on ice convert these to reactive Cl2, HOCl, which accumulate, trapped in ice • Spring daylight returns, solar radiation converts Cl2 to Cland HOCl to HO· and Cl • Sudden burst of Cl· reacts with O3, produces ClO· which forms ClO-OCl, which forms ClOO· and Cl· • Abundant Cldestroys lots of ozone • Chain is brokenwhen sunlight evaporates polar clouds , releasing bound HNO3; NO2 reacts with ClO· and traps it again

    17. The Ozone Hole through Time 194 DU 108 DU 1979 1989 82 DU 118 DU 2006 2010

    18. Ozonesondes

    19. Ozonesonde Measurements 2012 Courtesy of NOAA

    20. Ozone Hole Recovery? 2012 Ozone Hole 2nd smallest in last 20 years! Courtesy of NOAA

    21. Ozone and UV • Ozone in the atmosphere is directly correlated with the UV intensity at the Earth’s surface Most of the biologically harmful effects of ozone depletion are due to an increase in UV-B at the Earth’s surface. Too much UV-B at the Earth’s surface can lead to an increase in skin cancer, cataracts and other health problems.

    22. The Montreal Protocol

    23. History • 1974: Molina & Rowland (1974) Nature 249, 810-812 • Paper calls attention to dangers of CFC’s in ozone breakdown • 1978: U.S., Canada, Sweden and Norway ban CFCs as propellants • 1987: Montreal Protocol calls for decrease in CFCs to 50% of 1986 levels by 1999 • 1990: London Amendments call for complete CFCphase-out by 2000 • 1992: Copenhagen Amendments accelerate phase-out to 1996 • 1995: Molina & Rowland win Nobel Prize in Chemistry

    24. Montreal Protocol (1987) The 1987 Montreal Protocol on Substances that Deplete the Ozone Layer (as agreed in 1987) Preamble • The Parties to this Protocol, • Being Parties to the Vienna Convention for the Protection of the Ozone Layer, • Mindful of their obligation under that Convention to take appropriate measures to protect human health and the environment against adverse effects resulting or likely to result from human activities which modify or are likely to modify the ozone layer, • Recognizing that world-wide emissions of certain substances can significantly deplete and otherwise modify the ozone layer in a manner that is likely to result in adverse effects on human health and the environment, • Conscious of the potential climatic effects of emissions of these substances, • Aware that measures taken to protect the ozone layer from depletion should be based on relevant scientific knowledge, taking into account technical and economic considerations, • Determined to protect the ozone layer by taking precautionary measures to control equitably total global emissions of substances that deplete it, with the ultimate objective of their elimination on the basis of developments in scientific knowledge, taking into account technical and economic considerations, • Acknowledging that special provision is required to meet the needs of developing countries for these substances, • Noting the precautionary measures for controlling emissions of certain chlorofluorocarbons that have already been taken at national and regional levels, • Considering the importance of promoting international co-operation in the research and development of science and technology relating to the control and reduction of emissions of substances that deplete the ozone layer, bearing in mind in particular the needs of developing countries, • HAVE AGREED AS FOLLOWS: …

    25. Ratification of Montreal Protocol(July 2003) Countries that have NOT Ratified the Montreal Protocol (11 Countries)

    26. Ozone-Depleting Substances (ODS) The Montreal Protocol has slowed and reversed the emission and accumulation of ODSs in the stratosphere. Ozone Assessment, 2010

    27. ODP vs. GWP

    28. Radiative Forcing (RF) AR4, 2007

    29. Radiative Forcing (RF) AR4, 2007

    30. Radiative Forcing (RF) AR4, 2007

    31. ODP and GWP The Montreal Protocol has a dual benefit: protecting ozone and climate!

    32. Mass-Weighted Emissions ODP-Weighted Emissions GWP-Weighted Emissions Ozone Assessment, 2010

    33. Montreal Protocol Protects Climate Montreal Protocol decreases CO2-eq emissions by 11 Gt in 2010! Ozone Depletion Offset HFC Offset 3.0 0.9 ~11 Gt N.B. The reduction target for the Kyoto Protocol for 2008-2012 is 2 Gt. Ozone Assessment, 2010; Velders 2007

    34. Ozone and Climate

    35. Geopotential Height Trends and the Southern Annular Mode of Variability Thompson and Solomon 2002

    36. Climate Change Attribution • How do we attribute climate changes to greenhouse gases versus ozone depletion? • Use a global climate model, e.g.) Table of GCM simulations (Polvani et al., 2011)

    37. Climate Change Attribution • How do we attribute climate changes to greenhouse gases versus ozone depletion? • Use a global climate model, e.g.) Table of GCM simulations (Polvani et al., 2011)

    38. Climate Change Attribution • How do we attribute climate changes to greenhouse gases versus ozone depletion? • Use a global climate model, e.g.) Table of GCM simulations (Polvani et al., 2011)

    39. Climate Change Attribution • How do we attribute climate changes to greenhouse gases versus ozone depletion? • Use a global climate model, e.g.) Table of GCM simulations (Polvani et al., 2011)

    40. Climate Change Attribution • How do we attribute climate changes to greenhouse gases versus ozone depletion? • Use a global climate model, e.g.) Table of GCM simulations (Polvani et al., 2011)

    41. Climate Change Attribution • How do we attribute climate changes to greenhouse gases versus ozone depletion? • Use a global climate model, e.g.) Table of GCM simulations (Polvani et al., 2011)

    42. 20th Century Change:Attribution to Ozone and GHG Polvani et al. 2011a

    43. 20th Century Change:Attribution to Ozone and GHG Polvani et al. 2011a

    44. 21st Century Change:Attribution to Ozone and GHG Polvani et al. 2011b

    45. The “World Avoided”

    46. The “World Avoided” “No Montreal Protocol” EECL – Equivalent effective Chlorine (think of it as CFC’s) Garcia et al., 2012

    47. “World Avoided” Global Warming 21st Century Ts Change Control (Montreal Protocol) “World Avoided” (No Montreal Protocol) Averaged Over Longitudes Garcia et al., 2012

    48. UV Index “World Avoided” Values over 11 are considered “extreme” Present-day levels of ozone Garcia et al., 2012

    49. Ozone Depletion and Antarctic Sea Ice

    50. Antarctic sea ice extent is increasing Small + positive trend in Antarctic sea ice Data: NSIDC; http://www.columbia.edu/~mhs119/UpdatedFigures/