1. Introduction to Climatology (Geog 300 - 2009-02-05) - Paleoclimatology - Oliver Timm - IPRC-SOEST 1680 EAST WEST RD POST Bldg 413G timm@hawaii.edu Online introduction: http://www.ncdc.noaa.gov/paleo/primer.html http://www.ncdc.noaa.gov/paleo/primer.html  Textbooks: Bradley, R.S., 1999. "Paleoclimatology: Reconstructing Climates of the Quaternary". Academic Press, San Diego. “Ice ages : solving the mystery” by John Imbrie and Katherine Palmer Imbrie.

2. Tilt of the Ecliptic Ecliptic: The apparent path of the Sun's motion on the celestial sphere as seen from Earth.celestial sphere The ecliptic plane is tilted 23.5° with respect to the plane of theecliptic plane celestial equator. (The Earth's spin axis is tilted 23.5° with respect to its orbit around the sun.)

3. What causes the seasons? Tilted ecliptic  Cause for annual cycle in solar declination angle Incoming solar raditation S 0 (1367 W/m 2 ) Received energy per unit area on Earth surface: I= S 0 cos() 1m  Zeta

4. Basic Geometry Declination angle δ (delta) Solar zenith angle ζ (zeta) Elevation angle η (eta) Zenith Angle + Elevation Angle = 90 o Eq δ ϕ Honolulu latitude ϕ (phi) =21.5 o N ζ η

5. http://www.analemma.com/Pages/framesPage.html

6. http://en.wikipedia.org/wiki/Equation_of_time

7. Typical solar insolation annual cycle in Hawaii Dec Jan Jun

8. Observed rainfall (satellite and station data) present day annual cycle

9. x VE (vernal equinox) AE (autumn equinox) summer solstice WS Causes for our seasons: tilt of the ecliptic relative to the plane of the celestial equator The difference in the distance Sun-Earth is not the primary factor (6% changes in insolation) Earth closest to sun (Perihelion) on January 3rd, and most distant point (Aphelion) on July 4th winter solstice P A

10. x VE AE SS WS Kepler's second law and the length of seasons: The speed of the planet in its orbit is such that the connecting line from the planet to the sun skims over an equal area in equal time Kepler's second law and the length of seasons: The speed of the planet in its orbit is such that the connecting line from the planet to the sun skims over an equal area in equal time Johannes Kepler (1571-1630)

11. What would be the mean surface temperature according to Stefan-Boltzmann-Law? global mean climate state is described through the global mean air temperature at 2m  to be in an equilibrium: incoming energy = outgoing energy I in = I out I in = (1-a)*S o /4 = (1-a) * 1367 Wm -2 / 4 I in = (1-a) * 342 Wm -2 a is the albedo of the Earth: a ≈ 0.3 about 30% of incoming solar radiation is reflected into space I in ≈ 240 Wm -2

12. Radiative Equilibrium Temperature I in = I out I out = εσT 4 Emissivity of Earth surface in infrared wavelength (10 micron) is close to ε≈1 T 4 =I in /(εσ) = 240 Wm -2 /(5.67*10 -8 Wm -2 K -4 )

13. Radiative Equilibrium Temperature I in = I out I out = εσT 4 Emissivity of Earth surface in infrared (10 micron) is close to ε≈1 T 4 =I in /(εσ) = 240 Wm -2 /(5.67*10 -8 Wm -2 K -4 ) T= 253K = -18 o C = 0 o F Thanks to the atmospheric greenhouse effect we live in more friendly environment with about 15 o C global mean temperature

14. Balance between incoming and outgoing energy

15. Energy balance of the Earth Climate system

16. How can the mean global climate change? Imbalance in incoming and outgoing radiation  I in < I out : global temperature decrease  I in > I out : global temperature increase NOTE: THIS IS AN IDEALIZED WORLD!  OCEAN HEAT CAPACITY CAN BUFFER THE HEAT LOSS/GAIN!  climate shows different regional, seasonal characteristics anthropogenic CO 2 increase reduces I out

17. Energy balance of the Earth Climate system

18. instrumental observations indirect paleo observations Why has the study of past climates (Paleoclimatology) become so important for future climate change research?  We can look into the past to find climate analogs for the expected CO 2 levels  We can test the climate models how good they can reproduce past climates (e.g. ice-ages, warm phases)  Learn about the response of Greenland and Antarctic ice-sheets, vegetation, ocean acidification to rapid climate change

19. Glacial-Interglacial cycles In 18 th and early 19 th century acceptance of the idea of past ice ages. (rock formations, moraines in the Alpes, Agassiz, 1837) North America: similar geological formations Agassiz (1807-1873) Alaska, Mendenhall Glacier http://pubs.usgs.gov/of/2004/1216/ Northern Germany

20. Glacial-Interglacial cycles In 18 th and early 19 th century first evidence (and acceptance as proof) for an ice age (rock formations in the Alpes, Agassiz, 1837) Early (19 th century) explanations for ice ages:  Solar insolation changes  Volcanic dust  Interstellar dust  Changes in the ocean circulation  Vertical movements of the earth's crust  CO 2 reduction  Orbitally driven solar forcing Agassiz (1807-1873)

21. x VE (vernal equinox) AE (autumn equinox) summer solstice WS Causes for our seasons: tilt of the ecliptic relative to the plane of the celestial equator The difference in the distance Sun-Earth is not the primary factor (6% changes in insolation) Earth closest to sun (Perihelion) on January 3rd, and most distant point (Aphelion) on July 4th winter solstice P A

22. Orbital Theory Orbitally driven solar forcing: Adhemar 1839(?): Length of cold seasons (eccentricity + precession) Croll, 1867: Eccentricity + precession change in winter insolation Croll, 1875: additional factor: obliquity Milankovitch 1910s: quantification of orbitally driven insolation changes 1924: Koeppen, Wegener, Milankovitch: summer half-year high latitude insolation responsible for ice- ages 1941: Milankovitch: “Canon of the Insolation and the Ice Age Problem” James Croll (1821-1890) Milutin Milankovitch (1879-1958)

23. Precession 19,000+23,000 year periods Strong seasonal effect Eccentricity  100,000 yr period  Weak effect on annual insolation Obliquity 41,000 year period pole-equator contrast in insolation seasonal changes Precession depends on eccentricity Images: http://earthobservatory.nasa.gov/Library/Giants/Milankovitch/

24. more less Northern Hemisphere summer Insolation more less summer insolation at poles Orbital forcing over the last 150,000 years time Eccentricity Obliquity Eccentricity*Precession A. Berger (1978)

25. Effect of the Precession  changes the position of Perihelion and Aphelion with respect to the Vernal Equinox point  causes changes in the annual cycle of incoming solar radiation  a change in the length of the seasons

26. Typical solar insolation annual cycle in Hawaii Dec Jan Jun present 12,000 years ago

27. Evidence for 'Milankovitch Cycles' From 1950s on: finding evidence for orbital cycles in terrestrial and oceanic sediment records From 1990s to present Antarctic ice cores: Vostok, EPICA Dome C, Dome Fuji etc., covering last 800,000 years Cesare Emiliani (1922-1995) Sir Nickolas Shackelton (1937-2006) Wallace Broecker John Imbrie Ice ages : solving the mystery / John Imbrie and Katherine Palmer Imbrie. !

28. source http://www.ngdc.noaa.gov/paleo/ctl/index.html Glacial-Interglacial sea level changes: from the LGM to present about 120m sea level rise (about 400ft!!!) time 120m sea level rise

29. Simulated Ice Sheets 130,000-present (Abe et al., 2007) Simulated Ice Sheets 130,000-present (Abe et al., 2007) back

30. Sources of climatic information: climate proxies Any indirect information about the past climate!  Ice cores: isotopes, trace metals, annual layer thickness  Marine sediment cores: foraminifera assemblages, isotopes, trace metals, grain size, pollen  Tree ring width reflects climate of the growth season  Isotopes and trace metals from coral skeletons, speleothems  (Historical records: weather descriptions, harvest reports, famines etc.) What are climate proxies?

31. Climate proxies: A physical or chemical property of a given medium that is influenced by one or more components of the climate system.

32. Antarctic ice core record from EPICA time cooler Figure from http://www.realclimate.org/index.php?p=221 warmer CO 2 Greenhouse effect weaker stronger Last Glacial Maximum 20,000 years ago

33. Antarctic ice core record from EPICA warmer cooler Figure from http://www.realclimate.org/index.php?p=221 Last Glacial Maximum (LGM) 20,000 years ago CO 2 between 190-300 ppmv

34. Jouzel et al., Science 317, 2007 800,000 years climate history from Antarctica, Dome C present day climate part of the Holocence (present-10,000yrs ago) Last 10,000 years relatively stable. Pleistocene (10,000-1,800,000 yrs ago) LGM

35. Temperature and CO2 relationship: Lead and lags in the climate system Monnin et al., Science, 291, pp. 112-114, 2001 Temperature CO 2 increase begins warming starts Antarctica warming starts 18000 BP, CO 2 increase follows 800yr later LGM Holocene starts

36. Temperature and CO2 relationship: Lead and lags in the climate system Monnin et al., Science, 291, pp. 112-114, 2001 Temperature CO 2 increase begins warming starts Antarctica warming starts 18000 BP, CO 2 increase follows 800yr later

37. Temperature and CO2 relationship: Lead and lags in the climate system Ahn and Brook, Science, 322, 83-85, 2008 Millennial climate fluctuations: Antarctica warming and CO 2 increase in phase but Greenland warms after CO 2 increase

38. Understand climate change: Combination of paleoproxies

39. Lowell Stott, Axel Timmermann and R. Thunell, Science, 317, 2007 A new study co-authored by paleoclimatologist Lowell Stott of earth sciences indicates that carbon dioxide was not the main cause of the last ice age's meltdown. http://college.usc.edu/news/september_2007/stott.html Lowell Stott, USC Axel Timmerman n UH Manoa

40. Summary Orbital theory of ice ages (glacials) warm ages (interglacials):  precessional cycle (21,000 yr),  obliquity (tilt of the axis of rotation, 41,000 yr),  eccentricity (100,000 yr) Last glacial maximum (LGM) ended 20,000 years ago sea level rose by 120m from the LGM to present the recent Holocene epoch is relatively stable Paleoclimatogists still try to understand what caused the CO 2 changes during the glacial cycles from 190-300 ppmv.

41. Antarctic warming starts around 18,000 BP due to local insolation changes and CO 2 increase Southern hemispheric temperature evolution Only 35% of glacial-interglacial Transition can be Explained by CO2 Forcing Another 35% can be Explained in terms of Spring time insolation Southern hemispheric temperature evolution Only 35% of glacial-interglacial Transition can be Explained by CO2 Forcing Another 35% can be Explained in terms of Spring time insolation

42. Jan Feb Mar Apr May Jun Jul Aug sep Oct Nov Dec Jan 90N 90S Eq 60N 30N 30S 60S

43. Prolog: Earth's geologic time scale http://pubs.usgs.gov/gip/geotime/time.html

44. Geologic time scale

45. Taxonomy (Classification)  Eon  Era  Period  Epoch  Age  (Chronozone) http://www.stratigraphy.org /