1. MET 112 Global Climate Change – Lecture 7 Observations of Recent Climate Change Dr. Craig Clements San Jose State University Outline  How do we observe?  Recent trends in temperature  Recent trends in GHGs

2. What does ‘to observe’ mean?  Measurements –Of what?  Who compiles these measurements for governments and society?  IPCC: Intergovernmental Panel on Climate Change www.ipcc.ch Where do our observations come from? - to watch and record.

3. Temperature stations

4. Change in surface temperature in 20 th century

5. Bubbles Trapped in ice core Petit, Jean-Robert, et al (1999). “Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica”. Nature 399: 429-436.

6. Ice Core layers GISP2 ice core (Greenland Summit)GISP2ice core Archived at the National Ice Core Laboratory in CO. from 1837-1838 meters in which annual layers are clearly visible. The appearance of layers results from differences in the size of snow crystals deposited in winter versus summerwintersummer Counting such layers has been used (in combination with other techniques) to reliably determine the age of the ice. This ice was formed ~16250 years ago during the final stages of the last ice age and approximately 38 years are represented here.ice age

7. Ice Cores

8. Coring Earth’s ice sheets

9. Coring mountain glaciers

10. Time Series Analysis: Examples of Temperature Change  Trends  Periodic Oscillations  Random Variations  Jumps

11. Examples of Temperature Change  Draw the following: 1.Trend 2.Oscillation 3.Trend + Oscillation 4.Random variations 5.Random + trend 6.Jump 7.Random + jump

12. Trend 100806040200 Time Temperature

13. This graphs represents 1. Trend 2. Oscillation 3. Trend+Oscillation 4. Random variation 5. Random+Trend 6. Jump 7. Random+Jump 100806040200 Time Temperature

14. This graphs represents 1. Trend 2. Oscillation 3. Trend+Oscillation 4. Random variation 5. Random+Trend 6. Jump 7. Random+Jump

15. This graphs represents 1. Trend 2. Oscillation 3. Trend+Oscillation 4. Random variation 5. Random+Trend 6. Jump 7. Random+Jump

16. This graphs represents 1. Trend 2. Oscillation 3. Trend+Oscillation 4. Random variation 5. Random+Trend 6. Jump 7. Random+Jump

17. This graphs represents 1. Trend 2. Oscillation 3. Trend+Oscillation 4. Random variation 5. Random+Trend 6. Jump 7. Random+Jump

18. This graphs represents 1. Trend 2. Oscillation 3. Trend+Oscillation 4. Random variation 5. Random+Trend 6. Jump 7. Random+Jump

19. Time series of climate data

20. Time series of climate data

21. Time Frames -- Examples  Seconds to minutes – Small-Scale Turbulence  Hours – Diurnal Cycle (Caused by Earth’s Rotation)  Hours to Days – Weather Systems  Months – Seasonal Cycle (Caused by tilt of axis)  Years – El Niño  Decades -- Pacific Decadal Oscillation  Centuries – Warming during 20 th Century (Increase in greenhouse gases?)  Tens of thousands of Years – Irregularities in Earth’s motions  Millions of Years – Geologic Processes Climate Change Climate “Variability”

22. Time Series Data: High Frequency (10 Hz = 10 samples/sec)

24. Latest global temperatures

25. Temperature over the last 10 years

26. …“Over the last 140 years, the best estimate is that the global average surface temperature has increased by 0.7 ± 0.2°C” (IPCC 2007)  So the temperature trend is: 0.7°C ± 0.2°C  What does this mean?  Temperature trend is between 0.8°C and 0.4°C  The Uncertainty (± 0.2°C ) is critical component to the observed trend

27. Current CO 2 : ~383 ppm

28. What Changed Around 1800?  Industrial Revolution –Increased burning of fossil fuels  Also, extensive changes in land use began –the clearing and removal of forests

29. Ice core record

30. Increase in ocean temperature causes a decrease in the solubility of CO 2 in sea water (outgassing), which increases the atmospheric loading of CO 2 (Stott et al. 2007). In the Vostok Ice core, carbon dioxide concentrations lagged behind the temperature by about 600±400 years (Caillon et al. 1999). What caused the large temperature changes? Three cycles of the Earth’s orbit: called Milankovitch cycles

31. Milankovitch cycles: Eccentricity Earth’s orbit around the Sun (Earth-Sun Distance) The closest point to the Sun in a planet's orbit is called perihelion. The furthest point is called aphelion. 1. Eccentricity: “off-centerdness” of the orbit varies over time in a complicated way. Net result: two main cycles– one averages ~100,000 years and another about 400,000 years. When eccentricity is low there is little change through the year in the Earth-Sun distance. When eccentricity is high-the sunlight reaching Earth is ~20% stronger at perihelion than at aphelion.

32. Earth’s orbit around the Sun Eccentricity off-centerdness” of the orbit

33. Earth’s tilt: ranges from ~21.8º to 24.4º and changes over the course of ~41,000 years When the tilt is most pronounced, it allows for stronger summer Sun and weaker winter Sun– especially at high latitudes. Ice ages often set in as the tilt decreases: Because the progressively cooler summers can’t melt the past winter’s snow. At the other extreme, it can bring the Earth out of an ice age. Milankovitch cycles: Obliquity of the Earth’s Axis

34. Precession: Angular motion (wobble) of the Earth’s axis of rotation. - varies ~26,000 years. Milankovitch cycles: Precession of Earth’s Axis of Rotation.

35. 0º0º earth Precession Obliquity

36. Ice core CO 2 record

37. Retreat of mountain glaciers: ‘visual inspection’ Boulder Glacier, Mt. Baker, Washington

38. Retreat of mountain glaciers

39. Melting of Greenland Icesheet

40. Global rise in sea level last 20,000 years

41. Global rise in sea level in the 20 th century

42. Shorter winters in Alaska

44. Latest global temperatures

45. Instrumental Air Temperature Record 45  Averaged by decade

46. Current CO 2 : ~383 ppm

47. What Changed Around 1800?  Industrial Revolution –Increased burning of fossil fuels  Also, extensive changes in land use began –the clearing and removal of forests

49. Burning of Fossil Fuels  Fossil Fuels: Fuels obtained from the earth are part of the buried organic carbon “reservoir” –Examples: Coal, petroleum products, natural gas  The burning of fossil fuels is essentially –A large acceleration of the oxidation of buried organic carbon

50. Land-Use Changes  Deforestation: –The intentional clearing of forests for farmland and habitation  This process is essentially an acceleration of one part of the short-term carbon cycle: –the decay of dead vegetation  Also causes change in surface albedo (generally cooling)

53. Greenhouse Gases  Carbon Dioxide  Methane  Nitrous Oxide  CFCs (Chlorofluorocarbons)  Others

54. Methane

55. Anthropogenic Methane Sources  Leakage from natural gas pipelines and coal mines  Emissions from cattle  Emissions from rice paddies

56. Nitrous Oxide N 2 O

57. Anthropogenic Sources of Nitrous Oxide  Agriculture  Bacteria in Soils  Nitrogen fertilizers

58. CFCs (Chlorofluorocarbons) CFC-11 CFC-12

59. Sources of CFCs  Leakage from old air conditioners and refrigerators  Production of CFCs was banned in 1987 because of stratospheric ozone destruction –CFC concentrations appear to now be decreasing –There are no natural sources of CFCs

60. The Land and Oceans have both warmed

61. Precipitation patterns have changed