Presentation Transcript

1. Ozone LayerChapter 21, sections 9 and 10

2. Ozone layer A layer in the stratosphere that is made of ozone (O3) Absorbs ultraviolet light from the sun, protects organisms from damage to DNA, especially due to UVB Note the difference between stratospheric ozone (good) and tropospheric or ground-level ozone (a harmful secondary pollutant, but the same chemical, O3)
3. Early research on threats to the ozone layer SST – supersonic transport plane, or the Concorde, would be able to cross the Atlantic in a few hours, flying a very high altitudes, led to research on effects of water vapor on ozone but was essentially a non-issue because it never “took off” commercially, only 20 were ever built Space Shuttle program – a then-new law passed in 1969, National Environmental Policy Act (or NEPA) required an assessment of potential environmental impact of government projects, scientists reported that chlorine coming from the engines would destroy ozone
4. Early research on threats to the ozone layer F. Sherwood Rowland and Mario Molina – published a paper in 1974 in the journal Nature, showing that certain common industrial chemicals, called CFCs, would lead to the destruction of ozone when in the presence of sunlight Chlorofluorocarbons– these man-made chemicals were used many every day products, such as aerosol propellants, air conditioners, refrigerants – billions of pounds were produced every year
5. Summary of Reactions CCl3F + UV Cl + CCl2F Cl + O3 ClO + O2 Cl + O Cl + O2 Repeated many times Ultraviolet light hits a chlorofluorocarbon (CFC) molecule, such as CFCl3, breaking off a chlorine atom and leaving CFCl2. Sun Cl Cl C Once free, the chlorine atom is off to attack another ozone molecule and begin the cycle again. Cl F UV radiation Cl Cl O O A free oxygen atom pulls the oxygen atom off the chlorine monoxide molecule to form O2. The chlorine atom attacks an ozone (O3) molecule, pulling an oxygen atom off it and leaving an oxygen molecule (O2). Cl Cl O O O O O Cl The chlorine atom and the oxygen atom join to form a chlorine monoxide molecule (ClO). O O O
6. CFC Industry opposition – as early as 1976 One British scientist, Richard Scorer, was hired by the Chemical Specialties Manufacturer’s Association to tour the U.S. and publicly denounce the ozone depletion work – he called it “pompous claptrap,” even though it was presented in peer-reviewed scientific literature, argued that human impact would be too small to affect the immense atmosphere of the earth Why would the industry do this?
7. By 1977, use of CFCs as propellants had already dropped by 75% as the market and the American public gradually made changes (used pumps instead of spray cans, roll-on antiperspirants) U.S. government and federal agencies were already moving rapidly toward regulation of CFCs
8. Antarctic Ozone Hole First identified in 1985 by a team of British scientists – More accurately, a thinning of the ozone layer every spring over the poles, especially Antarctica Why? The very cold climate and clouds that form in winter lead to more ozone depletion (this research came later)
9. More recent data on Antarctic ozone hole 1979 2008 2010
10. Arctic Ozone Hole Ozone layer is also thinner at the Arctic For the first time since record-keeping began, destruction of the ozone layer over the Arctic in early 2011 was comparable to that in the Antarctic ozone hole, scientists report. [Nature]
11. NASA data – what trends do you see? The graphs above show the variations of ozone from year to year. The red bars indicate the largest area and the lowest minimum value. The year-to-year fluctuations are superimposed on a trend extending over the last three decades. http://ozonewatch.gsfc.nasa.gov/
12. Natural Capital Degradation Effects of Ozone Depletion Human Health Worse sunburn More eye cataracts More skin cancers Immune system suppression Food and Forests Reduced yields for some crops Reduced seafood supplies from reduced phytoplankton Decreased forest productivity for UV-sensitive tree species Wildlife Increased eye cataracts in some species Decreased population of aquatic species sensitive to UV radiation Reduced population of surface phytoplankton Disrupted aquatic food webs from reduced phytoplankton Air Pollution and Materials Increased acid deposition Increased photochemical smog Degradation of outdoor paints and plastics Global Warming Accelerated warming because of decreased ocean uptake of CO2 from atmosphere by phytoplankton and CFCs acting as greenhouse gases
13. Ultraviolet A Ultraviolet B Thin layer of dead cells Hair Epidermis Squamous cells Basal layer Sweat gland Melanocyte cells Dermis Basal cell Blood vessels Squamous Cell Carcinoma Basal Cell Carcinoma Melanoma
14. Skin Cancers Melanoma – most serious form of skin cancer
15. The Montreal Protocol addressed ozone depletion Montreal Protocol = 180 nations agreed to cut CFC production in half, 1987 Follow-up agreements deepened cuts, advanced timetables and addresses other ozone-depleting chemicals Today, production and use of ozone-depleting chemicals has decreased 95% The ozone layer is beginning to recover
16. The Montreal Protocol is a success Considered the biggest environmental success story The Montreal Protocol can serve as a model for international environmental cooperation
17. Other sources of opposition continued to deny the dangers of ozone depletion for years Example: Fred Singer, a cold-war physicist, not a climate scientist – from 1988-1995 argued that the “ozone research community was misleading the public about even the existence of ozone depletion, let alone its origins” (Merchants of Doubt, 2010) Also known for questioning the link between UVB and melanoma, dangers of secondhand smoke, and later global warming “Naomi Oreskes and Erik Conway named Singer in their book, Merchants of Doubt, as one of three contrarian physicists—along with Fred Seitz and Bill Nierenberg—who regularly inject themselves into the public debate about contentious scientific issues, positioning themselves as skeptics, their views gaining traction because the media gives them equal time out of a sense of fairness” (Wikipedia)
18. Challenges still face us CFCs will remain in the stratosphere for a long time Nations can ask for exemptions to the ban Replacement chemicals are also harmful to the environment “But demand for replacement substances called HCFCs, hydrochlorofluorocarbons, and HFCs, hydrofluorocarbons, has increased. Many of these are powerful greenhouse gases. HFC-23 is a byproduct of HCFC-22 production. Although it has no impact on the ozone layer it is more than 14,000 times more powerful as a climate-warming greenhouse gas than carbon dioxide, the most abundant greenhouse gas. Abundances and emissions of HFCs currently are increasing at about eight percent per year.” http://www.ens-newswire.com/ens/sep2010/2010-09-16-01.html