Presentation on theme: "Ozone and the Ozone Hole Heather Raven & Stefanie Spayd."— Presentation transcript:
Ozone and the Ozone Hole Heather Raven & Stefanie Spayd
Background Magnitude of polar O 3 loss depends on chlorine activation which is controlled by polar stratospheric clouds that depend on temperature (Tilmes et al., 2006) What are the important factors? Sunlight, Greenhouse Gases, and Temperature The Arctic also has an ozone hole, but has greater total column ozone than in the Antarctic because of dynamical re-supply of ozone (less O 3 loss) Antarctic has larger polar vortex and colder temps than Arctic = more concerned with O 3 at the southern pole (greater O 3 loss) New studies predict that no statistically significant change in ozone hole decrease will occur until about 2024 (Newman et al., 2006) Full recovery sometime between 2053 and 2084
Catalyst to breaking up the ozone layer. Breaks up O 3 into O 2 and O Breaks up CFCs to produce Cl Cl combines with Oxygen atoms, preventing them from combining with O 2 to form ozone. Thus, creating a lack of ozone molecules in the atmosphere. Sunlight
Greenhouse Gases and Ozone Hole Greenhouse gases warm the troposphere and cool the stratosphere. Polar stratospheric clouds (PSCs) contain molecules with chlorine, when the molecules react they form Cl 2 after which sunlight splits the molecule into Cl + Cl. PSCs form only in very cold stratosphere. Global warming is effectively enhancing ozone depletion! Stopping emission of GHGs now does not get rid of them right away: Important to note that CFCs have remained in atmosphere even after emission ceased due to Montreal Protocol (lifetime 65 – 400 years) The main players: Chlorofluorohydrocarbons (CFCs) CO 2 H 2 O
Temperature and Ozone Climate Change = Changing Temperature in the Stratosphere GHG ↑ Temperature ↓ Ozone hole duration ↑ (In Antarctic) Cooling of lower-stratosphere contributes to ozone loss: Chlorine activation below 195 K temps in stratosphere 195 K is threshold for formation of PSCs Antarctic below this threshold much of winter season Arctic below this threshold less in winter season, less ozone loss from chlorine
Take Home Points Continued anthropogenic release of greenhouse gases, not only CFCs, into the atmosphere will enlarge the ozone holes, letting more harmful UV rays reach the Earth’s surface. Temperature of the stratosphere is a key factor, as is sunlight, in the depletion of ozone. These processes are all intimately connected through chemical, radiative, and dynamical feedbacks.