CLIMATE CHANGE OVER THE LAST TWO MILLION YEARS

Transcription

1 CLIMATE CHANGE OVER THE LAST TWO MILLION YEARS 1. Introduction: forcings and feedbacks 2. Standing on the shoulders of giants: development of the Milankovitch theory 3. Evidence from the oceans, evidence from the ice 4. Pleistocene and Holocene 5. Abrupt climate change

2 Basic components of the climate system. Source: Ruddiman, 2001, p. 9.

3 Scientific ideas are continually tested and improved over time. If I have seen further, it is by standing on the shoulders of giants. Sir Isaac Newton, 1676.

4 How was this formed?? Lauterbrunnen, Switzerland. Source: J. Alean & M. Hambrey, Glaciers Online Photoglossary,

5 Why is this here?? Erratic boulders, Switzerland. Source: J. Alean & M. Hambrey, Glaciers Online Photoglossary,

6 How were these formed?? Lateral moraines, Switzerland. Source: J. Alean & M. Hambrey, Glaciers Online Photoglossary,

7 Louis Agassiz, Source: Riebeek, 2005,

8 Not to be confused with Andre Agassi.

9 Louis Agassiz, Source: Riebeek, 2005,

10 How was this formed?? Lauterbrunnen, Switzerland. Source: J. Alean & M. Hambrey, Glaciers Online Photoglossary,

11 Why is this here?? Erratic boulders, Switzerland. Source: J. Alean & M. Hambrey, Glaciers Online Photoglossary,

12 How were these formed?? Lateral moraines, Switzerland. Source: J. Alean & M. Hambrey, Glaciers Online Photoglossary,

13 Switzerland under ice. Source: Swiss Federal Office of Topography

14 The last glacial maximum ( ice age ).

15 Cyclical wobbles in the Earth s orbit: from Adhemar to Croll to Milankovitch. Source: Houghton, 2009, p. 86.

16 Source: Mann and Kump, 2009, p. 63.

17 Source: Mann and Kump, 2009, p. 63.

18 Source: Mann and Kump, 2009, p. 63.

19 Cyclical wobbles in the Earth s orbit. Source: Archer, 2012, p. 96.

20 Cyclical wobbles in the Earth s orbit. Source: Archer, 2012, p. 95.

21 Put em together and what have you got? Small differences between the extremes lead to glacial periods, roughly one every 100,000 years. Source: Encyclopedia of the Earth.

22 ATMOSPHERE The biological pump in the oceans OCEAN ~100 m mixed layer Wee beasties soak up carbon ~4900 m deep water Bodies, shells and skeletons sink to ocean floor

23 ATMOSPHERE The biological pump in the oceans OCEAN Wee beasties soak up carbon Bodies, shells and skeletons sink to ocean floor

24 Lots (and lots) of different species of zooplankton. Source: Tohoku University Museum,

25 A STEP BACK: REMINDER ABOUT THE NATURE OF MATTER

26 THE NATURE OF MATTER: Elements and compounds, atoms and molecules. Chemical element: A pure chemical substance composed of atoms with the same number of protons in the atomic nucleus. Chemical compound: A pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Source: International Union of Pure and Applied Chemistry Compendium of Chemical Terminology (Gold Book),

27 Schematic showing the structure of an oxygen atom. 8 electrons (-) Nucleus: 8 protons (+) (= atomic number)

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29 THE NATURE OF MATTER: Elements and compounds, atoms and molecules. Isotope: Atoms of the same element having the same atomic number but different mass numbers (atomic mass). Source: Mann and Kump, 2009, p. 201.

30 Schematic showing the structure of an oxygen atom. 8 electrons (-) Nucleus: 8 protons (+) 8, 9, or 10 neutrons Atomic number = 8 Atomic mass (mass number) = 16, 17 or 18 ( 16 O, 17 O or 18 O)

31 Two isotopes of oxygen: 16 O 18 O Which water molecules fall as snow near the poles? H 2 16 O H 2 18 O Which water molecules rain out more easily? Which water molecules evaporate more easily?

32 Bigger ice sheets separate out the isotopes More 16 O locked up in the ice sheets More 18 O remains in the oceans

33 Sea floor and ice core records of temperature. Source: Houghton, 2009, p. 83. Ocean sediments Vostok ice core

34 How ice coring works Source: Ruddiman, 2001.

35 NorthGRIP European ice coring project on Greenland. Source: NorthGRIP website,

36 Section of NorthGRIP ice core. Source: NorthGRIP website,

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39 Temperature relative to present (Celsius) Temperature derived from Vostok ice core: hydrogen isotope analysis (deuterium). Years before present Source: drawn using Vostok ice core data first published by JR Petit, available from World Data Center for Paleoclimatology,

40 Sea floor and ice core records of temperature. Source: Houghton, 2009, p. 83.

41 Some problems with basic Milankovitch theory: 1. Small forcing, large response 2. Symmetrical forcing, asymmetrical (saw-toothed) response 3. Identical response in northern and southern hemispheres

42 Temperature relative to present (Celsius) Temperature derived from Vostok ice core: hydrogen isotope analysis (deuterium). Years before present Source: drawn using Vostok ice core data first published by JR Petit, available from World Data Center for Paleoclimatology,

43 Some problems with basic Milankovitch theory: 1. Small forcing, large response 2. Symmetrical forcing, asymmetrical (saw-toothed) response 3. Identical response in northern and southern hemispheres FORCING RESPONSE What general concept might help explain this??

44 Sea floor and ice core records of temperature. Source: Houghton, 2009, p. 83.

45 CARBON DIOXIDE/TEMPERATURE FEEDBACK Arrange the terms and connect with arrows Goes up/down ORBITAL WOBBLES (Milankovitch forcing) CO 2 IN ATMOSPHERE CO 2 RELEASED FROM OCEANS TEMPERATURE

46 CARBON DIOXIDE/TEMPERATURE FEEDBACK ORBITAL WOBBLES (Milankovitch forcing) CO 2 IN ATMOSPHERE Goes up TEMPERATURE CO 2 RELEASED FROM OCEANS

47 Carbon dioxide (ppm) Temperature relative to present (Celsius) Temperature sometimes leads carbon dioxide Temperature and CO 2 in the Vostok ice core ~800 yr. lag CO Temperature Years before present Source: data from WDC Paleoclimatology

48 CARBON DIOXIDE/TEMPERATURE FEEDBACK At multi-million year timescales, the feedback is: negative At 100,000-year timescales, the feedback is: positive

49 Temperature relative to present (Celsius) Pleistocene and Holocene Holocene: the last 10,000 years Pleistocene: from ~2.5 million to 10,000 years ago Years before present 10,000 years ago Source: drawn using Vostok ice core data first published by JR Petit, available from World Data Center for Paleoclimatology,

50 Central Greenland temperature (Celsius) Central Greenland temperature estimated from GISP 2 stable isotopes Pleistocene Holocene WARM Years before present COLD Source: drawn using GISP2 ice core data first published by Richard Alley, available from World Data Center for Paleoclimatology,

51 Central Greenland temperature (Celsius) Abrupt climate changes in the ice core record: Dansgaard-Oeschger events and the Younger Dryas GISP 2 Central Greenland temperature WARM Dansgaard-Oeschger events Younger Dryas, 12 to 10.7 kyr BP Years before present COLD Source: drawn using GISP 2 ice core data first published by Richard Alley, available from World Data Center for Paleoclimatology,

52 If you're living with an angry beast, you shouldn't poke it with a sharp stick. Is this a good idea? Wallace Broecker, 2008 The Valley of Gwangi, Warner Bros., 1969.

53 This assumes that humans can act as a forcing on the global climate system. IS THIS A REASONABLE ASSUMPTION?