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Elevated CO 2 and Ozone: Causes & Consequences

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  1. Elevated CO2 and Ozone: Causes & Consequences Bill Holmes University of Michigan School of Natural Resources& Environment

  2. Presentation Outline • Part I: Rising atmospheric CO2 & tropospheric ozone • Sources & trends • Part II: Impacts on plants & ecosystems • Research questions, approaches, and findings • Part III: Activities • Calculate your carbon footprint • View ozone maps, action day alerts

  3. The Greenhouse Effect

  4. Greenhouse Gases

  5. Major Sources of CO2

  6. Global Carbon Budget

  7. Distribution of Emissions1995 annual totals by region Carbon Dioxide Information Analysis Center 2003

  8. 370 ppmtoday Atmospheric CO2 Record 299 ppmv, highest inlast 420,000 years

  9. Seasonal Oscillations in Atmospheric CO2 Concentration

  10. Major Consequences I • Rising temperatures • Increase in U.S. of 5-9 ºF by 2100 • Extreme weather • More frequent heavy precipitation events • Some regions get drier • Coastal and permafrost areas vulnerable • Sea level change • Storm surges • Sinking buildings and roads in Alaska

  11. Major Consequences II • Water quality impacts • Floods and droughts wreak havoc, especially in developing countries • Public health concerns • Floods, water borne diseases • Heat stress, air pollution • Agriculture & forestry impacts • CO2 promotes productivity, but… • More droughts, fire, and pest damage

  12. Major Consequences III • Ecosystem changes • Climate will change faster than ecosystems can migrate or adapt • Changes in plant competition • Grasslands invade forests in southeast U.S • Change in disturbance regimes – more fire!

  13. 80 80 60 60 40 40 20 20 0 0 1870 1870 1890 1890 1910 1910 1930 1930 1950 1950 1970 1970 1990 1990 Tropospheric Ozone Record O3 Concentration (ppbv) O3 Concentration (ppbv) Redrawn from: Marenco et al. 1994. J. Geophy. Res. 99: 16,617-16,632

  14. Good Ozone, Bad Ozone Too little there... CFC’s and halons from air conditioners and refrigerators break down the protective ozone layer. Too much here... Vehicles, power plants and factories emit air pollution that forms ground-level ozone.

  15. Sources of Ground-Level Ozone NOx, VOC + sunlight Ozone Hot sunny days

  16. Global Distribution of Tropospheric Ozone

  17. Tropospheric Ozone Circulation

  18. Effects of "Bad" Ozone • Human Health • Coughing, throat irritation, lung damage • Worse when working or exercising outdoors • The Environment • Damages vegetation and ecosystems • Increases susceptibility of trees to other stresses (pests, diseases, weather extremes) • Forest and crop losses

  19. Part II: Impacts on Plants & Ecosystems ? Climate Change temperature air pollution carbon dioxide ozone Ecosystem Function plant growth nutrient cycling carbon sequestration

  20. Carbon and Nitrogen Cycling in Terrestrial Ecosystems Plant Productivity Plant Litter Biochemistry Soil Nitrogen Availability Substrate Availability Microbial Community Composition & Function

  21. Carbon and Nitrogen Cycling in Terrestrial Ecosystems Atmospheric CO2 & O3 Plant Productivity Plant Litter Biochemistry Soil Nitrogen Availability Substrate Availability Microbial Community Composition & Function Atmospheric N Deposition

  22. Carbon and Nitrogen Cycling in Terrestrial Ecosystems Atmospheric CO2 & O3 Plant Productivity Plant Litter Biochemistry Soil Nitrogen Availability Temperature & Precipitation Substrate Availability Microbial Community Composition & Function Atmospheric N Deposition

  23. Free-Air CO2 Enrichment (FACE) Experiments Open-air control of atmosphere conditions Fairly large scale Longer term than previous chamber experiments Major investment of research money Large teams of researchers

  24. Free-Air CO2 Enrichment (FACE) Sites

  25. Eastern U.S. FACE Sites Cedar Creek, MN Rhinelander, WI Oak Ridge, TN Durham, NC

  26. Aspen FACE ExperimentRhinelander, WI

  27. Experimental Design 4 treatments x 3 blocks = 12 rings AmbientControl ElevatedCO2 ElevatedO3 ElevatedCO2 + O3 360 32 560 32 360 56 560 56 ppm CO2: ppb O3:

  28. Aspen FACE Site Aspen-Birch Aspen Aspen-Maple

  29. Why Study Aspen & Birch? Global Geographic Distribution (white & stippled areas)

  30. Research Questions • Will more or less CO2 be sequestered by forest trees or in soil as CO2 levels rise? • Will elevated CO2 alleviate other stresses (e.g. ozone, drought, low fertility)? • What are the interactive effects of CO2 and ozone?

  31. CO2 and Ozone Effects CO2 effects: + photosynthesis + growth + water use efficiency O3 effects: –photosynthesis – growth + leaf senescence

  32. Cell-level Ozone Damage Normal aspen chloroplast Large starch grains Intact thylakoid membranes Ozone damaged chloroplast Disintegration of thylakoid membrane Membrane degradation material Small starch grains

  33. CO2 and O3 Effects on Tree Growth 8000 Foliage Aspen Aspen-Birch Stems & Branches b b Coarse Roots Fine Roots 6000 a a Cumulative Net Primary Productivity g m-2 a Aspen-Maple b a 4000 c ab a a a 2000 0 CO2 CO2 CO2 Control Control Control O3 O3 O3 CO2 + O3 CO2 + O3 CO2 + O3

  34. Research Findings I • Tree growth increases under elevated CO2 and decreases under O3 • Carbon sequestration under elevated CO2 is overestimated in models which do not consider O3 impacts • O3 reduces the protective coating of leaves and damages leaf tissues • CO2 reduces the damaging effects of O3 and O3 reverses growth stimulation by CO2

  35. Research Findings II • Biogeochemical cycling of C and N increases under elevated CO2, but effects differ among FACE sites • O3 counteracts most CO2-induced enhancements in ecosystem processes (soil respiration, N availability…) • Plant response to CO2 may be limited by N availability or co-exposure to O3 or other factors. • Elevated CO2 delays normal autumn leaf senescence, predisposing some trees to winter dieback • Aspen and birch insects and diseases increase under elevated CO2 and O3

  36. Part III: Activities • What you and your students can do… • Find ways to reduce CO2 emissions • Learn about ozone action days • Get on the web! • Calculate your carbon footprint • View ozone maps and action day alerts

  37. Reduce CO2 Emissions • Reduce home heating & cooling energy use • Reduce transportation energy use • Increase energy efficiency • Learn about implementation of Kyoto protocol guidelines in other countries (Canada, UK) • Carbon offsets: reforestation and forest conservation programs

  38. Avoid and Reduce “Bad” Ozone • Check local air quality forecast • Limit physical exertion outdoors in afternoon and early evening • Ozone action days • Conserve energy • Avoid driving or filling up fuel tank • Avoid using lawn mower or other two-stroke powered equipment

  39. Ideas • Find and compare different carbon calculators • Build your own carbon calculator • Look up unit conversions Ex: CCF to therms for natural gas • Brainstorm ideas for CO2 offsets • Learn about Kyoto protocol