Greenhouse Effect & Global Warming

1. Greenhouse Effect & Global Warming

2. Some Evidence The global air temperature at the Earth's surface has increased about 0.5oC during the past century

5. Sun Solar Energy Earth’s Temperature

10. Greenhouses are used to grow plants, especially in the winter. The glass panels of the greenhouse let in light but keep heat from escaping. This causes the greenhouse to heat up, like the inside of a car parked in sunlight, and keeps the plants warm enough to live in the winter. The Greenhouse

12. Greenhouse Glass, the material that greenhouse is made of, 1) transmit short-wavelength visible light, 2) absorbs and redirects the longer wavelengths of energy. These two aspects make the greenhouse warmer than outside air temperature.

13. Greenhouse effect of the atmosphere • Light from the sun includes the entire visible region and smaller portions of the adjacent UV and infrared regions. • Sunlight penetrates the atmosphere and warms the earth’s surface. • Longer wavelength infrared radiation is radiated from the earth’s surface. • A considerable amount of the outgoing IR radiation is absorbed by gases in the atmosphere and reradiated back to earth. The gases in the atmosphere that act like glass in a greenhouse are called greenhouse gases.

14. Natural Greenhouse effect The natural greenhouse effect causes the mean temperature of the Earth's surface to be about 33oC warmer than it would be if natural greenhouse gases were not present.

15. Enhanced greenhouse effect When concentrations of greenhouse gases increase, more infrared radiation is returned toward the earth and the surface temperature rises.

16. What makes a gas greenhouse gas? Able to absorb infrared light • Must have molecular vibration(s) • The molecular vibrations must be non-symmetric, i.e. infrared active • Homonuclear diatomic molecules only have symmetric vibrations. That’s why N2, O2 are not greenhouse gases.

17. What are the major greenhouse gases? • H2O • CO2 • CH4 • N2O • O3 • CFCs

18. Carbon Dioxide

19. Are human beings causing increases in greenhouse gases?

20. CO2 Concentrations at Mauna Loa, Hawaii The average atmospheric CO2 concentrations observed at Muana Loa, Hawaii increased approximately 40 ppmv between 1958 and 1995.

21. Rate of increase: 0.9% annually Methane Atmospheric methane has increased steadily to present day levels; this increase is highly correlated with human population growth and with related activities, including agricultural practices.

22. Nitrous oxide (N2O) Rate of increase 0.25%/year Use of fertilizer increases both nitrification and denitrification  increase N2O production

23. CFC-11

24. Is the earth getting warmer?

25. Temperature over the past one century The global air temperature at the Earth's surface has increased about 0.5oC during the past century

26. Temperature over the past 1000 years

27. Carbon Dioxide

28. Sources and sinks of CO2 • Sources • Natural: respiration of vegetation and soil detritus • Man-made: Fossil fuel combustion, deforestation • Sinks: slow exchange of carbon between surface waters and deep layers of ocean. (Seawater is alkaline while CO2 is acidic  The oceans are a vast reservoir of CO2).

29. Worldwide Carbon Emissions Total Liquid fuel Solid fuel Gas fuel 8 7 6 5 Carbon (109 metric tons) 4 3 2 1 0 1750 1800 1850 1900 1950 2000 Year

30. Future Carbon Dioxide Levels • Increasing CO2 emissions, especially in China and developing countries • Likely to double within 150 years: • Increased coal usage • Increased natural gas usage • Decreased petroleum usage (increased cost and decreasing supply)

31. Status of CO2 Pre-industrial Amount: 280 ppm Present Amount: 382 ppm Maximum Allowable ≤ 450 ppm Rate of Change: +2 ppm/year (and growing)

32. Kyoto Protocol • Adopted in 1997 • Cut CO2 emissions by 5% from 1990 levels for 2008-2012 • Symbolic only, since cuts will not significantly impact global warming

33. CO2 Concentration Vs. Temperature 370 320 31 30 SST (°C) Tropical Pacific CO2 (ppm) Antarctica 270 29 28 220 27 26 170 25 600000 400000 200000 0 Time (YBP)

34. More Important Data

36. Greenhouse Effect & Global Warming • The “greenhouse effect” & global warming are not the same thing. • Global warming refers to a rise in the temperature of the surface of the earth • An increase in the concentration of greenhouse gases leads to an increase in the themagnitude of the greenhouse effect. (Called enhanced greenhouse effect) • This results in global warming

37. Consequences of global warming • Sea level rise • Beach erosion • Coastal wetland loss • Loss of low-lying territories • Water resources change • Precipitation pattern shift • Increases instances of heavy precipitation • Effects on agriculture • Changes in the length of growing season • Growth of undesirable plant species

38. Consequences of global warming (Continued) • Effects on air quality • Increase in reaction rates and concentrations of certain atmospheric species increase in O3 in urban areas • Impacts on human health • Changes in patterns of sickness and death. • Respiratory problems affected by air quality change • Biodiversity • Some species may grow too quick and overshoot their reproductive period (e.g. reef corals) • Change in the pattern of ocean current

39. Possible Solutions to Global Warming

40. Mitigation of Global Warming • Conservation • Reduce energy needs • Recycling • Alternate energy sources • Nuclear • Wind • Geothermal • Hydroelectric • Solar