SOES 6047 Global Climate Cycles SOES 6047 Global
SOES 6047 - Global Climate Cycles SOES 6047 Global Climate Cycles L 6: Research Themes: Quaternary glacialinterglacial cycles Dr. Heiko Pälike heiko@noc. soton. ac. uk Ext. 23638, Rm. 164/34
SOES 6047 - Global Climate Cycles � Ice-core records: where are they from, and what can they tell us? � Found strong correlation of T°C and CO 2, over at least the past ~400, 000 years � Range of CO 2 variations between 180– 280 ppmv L 6 Themes: Quaternary glacial-interglacial cycles Last “themes” lecture: 2
SOES 6047 - Global Climate Cycles � Historical overview of the understanding of Quaternary glacialinterglacial cycles and changes � Observations of glaciations � Oxygen isotope record of glaciations � magnitude � sea-saw pattern � Sea-level or temperature? � Orbital (Milankovitch) component � sub-orbital (millenial scale) component � 100 kyr vs 41 kyr “world”: Problems with insolation forcing � Ocean chemistry changes L 6 Themes: Quaternary glacial-interglacial cycles Lecture outline 3
SOES 6047 - Global Climate Cycles Some references L 6 Themes: Quaternary glacial-interglacial cycles Berger, A. , et al. , eds. , Milankovitch and Climate, NATO ASI Series, vol. 126 (2 parts) (Reidel Publishing Company, 1984). Broecker, W. S. & Peng, T. H. , Tracers in the Sea (Lamont-Doherty Geological Observatory, Palisades, N. Y. , 1982). Emiliani, C. (1955), ‘Pleistocene temperatures’, Journal of Geology 63. Fairbanks, R. G. (1989), ‘A 17, 000 -year glacio-eustatic sea-level record: Influence of glacial melting rates on the Younger Dryas Event and deep-ocean circulation’, Nature 342, 637– 642. Flückiger, J. , et al. (2002), ‘High resolution Holocene N 2 O ice core record and its relationship with CH 4 and CO 2’, Global Biogeochemical Cycles 16, 1010. Gallée, H. , Berger, A. , & Shackleton, N. J. , ‘Simulation of the climate of the last 200 kyr with the LLN 2 D-model’, Ice in the Climate System, W. R. Peltier, ed. (Springer-Verlag, Berlin, 1993), NATO ASI Series, vol. 1, 321– 341. Gallée, H. , et al. (1992), ‘Simulation of the last glacial cycle by a coupled, sectorially averaged climate-ice-sheet model. II. Response to insolation and CO 2 variation’, Journal of Geophysical Research 97, 15713– 15740. Hays, J. D. , Imbrie, J. , & Shackleton, N. J. (1976), ‘Variations in the Earth’s orbit: Pacemaker of the Ice Ages’, Science 194, 1121– 1132. Herbert, T. D. , et al. (2001), ‘Collapse of the California Current during Glacial Maxima Linked to Climate Change on Land’, Science 293, 71– 76. Huybers, P. & Wunsch, C. (2005), ‘Obliquity pacing of the late Pleistocene glacial terminations’, Nature 434, 491– 494. Kawamura, K. et al. , ‘Northern Hemisphere forcing of climatic cycles in Antarctica over the past 360, 000 years’, Nature 448, 912– 916 (2007). Imbrie, J. & Imbrie, J. Z. (1980), ‘Modeling the climatic response to orbital variations’, Science 207. Imbrie, J. & Imbrie, K. P. , Ice Ages – Solving the mystery (Harvard University Press, Cambridge, MA, 1979). Imbrie, J. , et al. , ‘The orbital theory of Pleistocene climate: Support from a revised chronology of the marine d 18 O record’, Milankovitch and Climate (Part I), A. Berger et al. , eds. (D. Reidel, Norwell, Mass. , 1984), 269– 305. Imbrie, J. et al. , ‘Oceanic response to orbital forcing in the Late Quaternary: observational and experimental strategies’, Climate and Geo-sciences, A. Berger et al. , eds. (Kluver, 1989), 121– 164. Imbrie, J. , et al. (1992), ‘On the structure and origin of major glaciation cycles, 1. linear responses to Milankovitch forcing’, Paleoceanography 7, 701– 738. Imbrie, J. , et al. (1993), ‘On the structure and origin of major glaciation cycles, 2. the 100, 00 -year cycle’, Paleoceanography 8, 699– 735. Karner, D. B. , et al. (2002), ‘Constructing a stacked benthic d 18 O record’, Paleoceanography 17, 1030. Lambeck, K. & Chappell, J. (2001), ‘Sea level change through the last glacial cycle’, Science 292, 679– 686. Lambeck, K. , Yokoyama, Y. , & Purcell, T. (2002), ‘Into and out of the Last Glacial Maximum: sea-level change during Oxygen Isotope Stages 3 and 2’, Quaternary Science Reviews 21, 343– 360. 4
SOES 6047 - Global Climate Cycles Some references L 6 Themes: Quaternary glacial-interglacial cycles Lisiecki, L. E. & Raymo, M. E. (2005), ‘A Pliocene-Pleistocene stack of 57 globally distributed benthic d 18 O records’, Paleoceanography 20, PA 1003. Loutre, M. F. & Berger, A. (2000), ‘No glacial-interglacial cycle in the ice volume simulated under a constant astronomical forcing and a variable CO 2’, Geophysical Research Letters 27, 783– 786. Monnin, E. , et al. (2001), ‘Atmospheric CO 2 concentrations over the last glacial termination’, Science 291, 112– 114. Muller, R. A. & Mac. Donald, G. J. (1997), ‘Glacial Cycles and Astronomical Forcing’, Science 277, 215– 217. Muller, R. A. & Mac. Donald, G. J. , Ice Ages and Astronomical Causes: Data, Spectral Analysis and Mechanisms (Springer-Verlag, 2000). Paillard, D. (1998), ‘The timing of Pleistocene glaciations from a simple multiple-state climate model’, Nature 391. Petit, J. R. , et al. (1999), ‘Climate and atmospheric history of the past 420, 000 years from the Vostok ice core, Antarctica’, Nature 399, 429 – 436. Rahmstorf, S. , 2007 a: A semi-empirical approach to projecting future sea-level rise. Science (Express), 10. 1126/science. 1135456. Rahmstorf, S. , et al. 2007 b: Recent Climate Observations Compared to Projections. Science (Express), 10. 1126/science. 1136843. Raymo, M. E. (1997), ‘The timing of major climate terminations’, Paleoceanography 12, 577– 585. Raymo, M. E. & Nisancioglu, K. (2003), ‘The 41 kyr workd: Milankovitch’s other unsolved mystery’, Paleoceanography 18, 1001. Raymo, M. E. , Oppo, D. W. , & Curry, W. (1997), ‘The mid-Pleistocene climate transition: A deep-sea carbon isotope perspective’, Paleoceanography 12, 546– 559. Ruddiman, W. F. , Earth’s climate: Past and Future (W. H. Freeman and Company, 2001). Shackleton, N. J. (2000), ‘The 100, 000 -year ice-age cycle identified and found to lag temperature, carbon dioxide, and orbital eccentricity’, Science 289, 1897– 1902. Shackleton, N. J. & Pisias, N. G. , The Carbon Cycle and Atmospheric CO 2: Natural Variations Archean to Present (American Geophysical Union, 1985), Geophysical Monograph Series, vol. 32, Atmospheric carbon dioxide, orbital forcing, and climate, 412– 417. Shackleton, N. J. , et al. (2004), ‘Absolute calibration of the Greenland time scale: implications for Antarctic time scales and for 14 C’, Quaternary Science Reviews 23, 1513– 1522. Thompson, W. G. & Goldstein, S. L. (2005), ‘Open-system coral ages reveal persistent suborbital sea-level cycles’, Science 308, 401– 404. Tiedemann, R. , Sarnthein, M. , & Shackleton, N. (1994), ‘Astronomic timescale for the Pliocene Atlantic d 18 O and dust flux records of ODP Site 659’, Paleoceanography 9, 619– 638. Voelker, A. H. L. , et al. (1998), ‘Correlation of marine 14 C ages from the Nordic Seas with the GISP 2 isotope record: Implications for 14 C calibration beyond 25 ka BP’, Radiocarbon 40, 517– 534. Winograd, I. J. , et al. (1992), ‘Continuous 500, 000 -Year Climate Record from Vein Calcite in Devils Hole, Nevada’, Science 258, 255– 259. Wunsch, C. (2004), ‘Quantitative estimate of the Milankovitch-forced contribution to observed Quaternary climate change’, Quaternary Science Reviews 23, 1001– 1012. Zachos, J. C. , et al. (2001), ‘Trends, rhythms, and aberrations in global climate 65 Ma to present’, Science 292, 686– 693. 5
SOES 6047 - Global Climate Cycles � Why is it important to study the geological record of past glaciations and de-glaciations? � they are the KEY to understand present-day � mechanisms � time scales � interaction of the climate system � response to external forcing � Combination of a multitude of different data necessary: � geological observations (beach terraces, glacial striations) � geochronology (sea-level from, e. g. , exact dating of corals) � palaeoceanographic observations (marine isotope records, productivity and dust indicators) � ice-core records (only record of atmospheric gases) � modelling studies to evaluate whether response time of processes fits with data L 6 Themes: Quaternary glacial-interglacial cycles Bigger picture: 6
SOES 6047 - Global Climate Cycles � Palaeoceanography and glacial-interglacial changes are a young science: As a “respectable” scientist during year XX you wouldn’t have believed that: 1850: massive glaciers once covered the northern continents 1900: the Earth is older than 20 -40 Myr 1950: there have been more than 4 major advances and retreats of continental glaciers in the past 2 Myr 1965: Ice advances and retreats are (at least partially) paced by variations in the Earth’s orbit L 6 Themes: Quaternary glacial-interglacial cycles Historical overview 7
SOES 6047 - Global Climate Cycles � For an excellent historical overview, see: � Imbrie & Imbrie (1979), “Ice Ages – Solving the Mystery”, Harvard University Press � Berger, A. , et al. (Eds. ), “Milankovitch and Climate”, NATO ASI Series, vol. 126 (2 parts) (Reidel Publishing Company, 1984). (this is the outcome of a workshop held in 1982) � Ruddiman, W. F. , Earth’s climate: Past and Future (W. H. Freeman and Company, 2001). � 1840: Agassiz proposed massive glaciations based on geological observations � 1860: Croll prposed that changes in Earth’s orbital parameters responsible for glaciation - mixed response � 1920: Milankovitch undertook detailed calculations of insolation variations � 1950: Emiliani found additional evidence in oxygen isotopes Problem: time scale � 1960’s; 70’s: Barbados sea-level data from corals revived interest � 1976: Hays, Imbrie & Shackleton paper (Science): a MUST READ!!! � Today: continued research, but still problems associated with the past 800 kyr (why oscillations on a 100 kyr time scale? ) L 6 Themes: Quaternary glacial-interglacial cycles Historical overview (II) 8
SOES 6047 - Global Climate Cycles � vertical: long known observations of “raised beaches” and terraces as geological evidence of relative sea-level change, but could be tectonic, of course. Photo: raised beach terrace from Oman. Courtesy of Dr. Gideon Henderson, University College, Oxford, UK � Yet, also evidence for several generations of glacial endmoraines � can be used to map extent of Last Glacial Maximum NH ice-sheets Photo: glacial end-moraine in Antarctica, Flickr L 6 Themes: Quaternary glacial-interglacial cycles Sea-level observations 9
SOES 6047 - Global Climate Cycles Emiliani interpreted this record in terms of temperature (ca. 6°C difference)! NOTE THE USE OF ISOTOPE STAGES: GLACIAL=EVEN; INTERGLACIAL=ODD From Emiliani, C. (1955). Pleistocene temperatures, Journal of Geology v. 63, p. 538 -578. The University of Chicago Press. L 6 Themes: Quaternary glacial-interglacial cycles Emiliani’s first stable isotope record 10
SOES 6047 - Global Climate Cycles � extremely influential paper � statistically demonstrated that the stable isotope record of the last few glacial cycles was consistent with astronomical forcing From: Hays, J. D. , Imbrie, J. , Shackleton, N. J. (1976). ‘Variations in the Earth’s orbit: Pacemaker of the Ice Ages. Science. v. 194, v. 1121– 1132. Reprinted with permission from AAAS. These figures may be used for non-commercial, classroom purposes only. Any other uses require the prior written permission from AAAS. L 6 Themes: Quaternary glacial-interglacial cycles Hays, Imbrie & Shackleton 1976 11
12 SOES 6047 - Global Climate Cycles � SPECMAP (Imbrie et al. 1984, 1992, 1993) shows: � The current interglacial (Holocene) has low ice volume and is very stable - STAGE 1 � The Last Glacial Maximum had large ice volume - STAGE 2 � Warmer in STAGE 3, cooling into STAGE 4 � The last interglacial (Eemian or Ipswichian) had low ice volume but was very complex STAGES 5 a, 5 b, 5 c, 5 d and 5 e � However, the oxygen isotope record gives no geography about the ice masses � SPECMAP= “stacked” record from several Sites, normalised to standard deviation units � data: http: //gcmd. nasa. gov/records/GCMD_EARTH_LAND_NGDC_PALEOCL_SPECMAP. html Could not identify the source. was it drawn from the data found on the net? L 6 Themes: Quaternary glacial-interglacial cycles SPECMAP
13 SOES 6047 - Global Climate Cycles � related isotopic variations to Milankovitch astronomical calculations Schematic plot indicating From: Hays, J. D. , Imbrie, J. , Shackleton, N. J. (1976). ‘Variations in the Earth’s orbit: Pacemaker of the Ice Ages. Of Southampton Science. v. 194, v. 1121– 1132. Reprinted with permission from AAAS. This figure may be used for non commercial, classroom purposes only. Any other uses require the prior written permission from AAAS. relative amplitude of Milankovitch cycles, University L 6 Themes: Quaternary glacial-interglacial cycles SPECMAP (II)
14 SOES 6047 - Global Climate Cycles � After the publication of the Hays 1976 paper, and SPECMAP, there were several publications that doubt the astronomical origin of these cycles � Muller & Mac. Donald (1995, 1997, 2000) � claim that orbital inclination is responsible (no split 100 kyr peak) � but how get 41 kyr cycles? they did not look at long enough records � Winograd et al. (1992) use U/Th dated calcite vein in cave record to argue that warming took place before insolation changes � But: local climate signal, not marine? (also see Herbert, 2001) From: Muller, R. A. & Mac. Donald, G. J. (1997). Glacial Cycles and Astronomical Forcing’, Science. v. 277, p. 215– 217. Reprinted with permission from AAAS. This figure may be used for non-commercial, classroom purposes only. Any other uses require the prior written permission from AAAS. From: Winograd, I. J. , Coplen, T. B. , Landwehr, J. M. , Riggs, A. C. , Ludwig, K. R. , Szabo, B. J. , Kolesar, P. T, and Revesz K. M. , (1992) Continuous 500, 000 -Year Climate Record from Vein Calcite in Devils Hole, Nevada. Science, v. 258, p. 255 -260. Reprinted with permission from AAAS. This figure may be used for non-commercial, classroom purposes only. Any other uses require the prior written permission from AAAS. L 6 Themes: Quaternary glacial-interglacial cycles Criticism
SOES 6047 - Global Climate Cycles � After the publication of the Hays 1976 paper, and SPECMAP, there were several publications that doubt the astronomical origin of these cycles � Wunsch (2004) argues that climate record is stochastic, with only very little astronomical forcing � Huybers & Wunsch (2005) argue that 100 kyr “sea-saw” pattern is actually resonance of 41 kyr cycles L 6 Themes: Quaternary glacial-interglacial cycles Criticism of eccentricity forcing 15
SOES 6047 - Global Climate Cycles � Beyond the past ~800 kyr, rather than showing the typical glacial-interglacial 100 kyr sea-saw pattern, a 41 kyr pattern emerges From: Lorraine Lisiecki http: //lorraine-lisiecki. com/stack. html L 6 Themes: Quaternary glacial-interglacial cycles The Pleistocene-Pliocene story 16
17 SOES 6047 - Global Climate Cycles � different climatic regimes apparent -- why? Accessed from: http: //www. odplegacy. org/PDF/Admin/JOIDES_journal/J J_2002_V 28_No 1. pdf. by Rainer Zahn with data from: Tiedemann et al. 1994. L 6 Themes: Quaternary glacial-interglacial cycles Is the Quaternary unusual ?
18 SOES 6047 - Global Climate Cycles � Raymo & Nisancioglu (2003) suggest 41 kyr imprint through low-latitude insolation gradient Reproduced by permission of American Geophysical Union: Raymo, M. E. , Nisancioglu, K. , The 41 kyr workd: Milankovitch’s other unsolved mystery’, Paleoceanography. v. 18, p. 1001. Copyright [2003] American Geophysical Union. L 6 Themes: Quaternary glacial-interglacial cycles Insolation gradients?
19 SOES 6047 - Global Climate Cycles � A coupled ocean-atmosphere-ice model (zonally averaged): The “LLN-2 D” model manages to reproduce glacial interglacial cycles (Gallée et al. , 1993, 1997) � It also does NOT give glacial-interglacial cycles with variable (Vostok) CO 2 and no astronomical forcing (Loutre & Berger 2000) Reproduced by permission from Macmillan Publishers Ltd: Pillard, D. , The Timing of Pleistocene glaciations from a simple multiple State climate model. Nature, v. 391, p. 378 -381. Copyright (1998) Nature Publishing Group. L 6 Themes: Quaternary glacial-interglacial cycles Model results
SOES 6047 - Global Climate Cycles � Paillard (1998) suggests that 100 kyr world due to threshold behaviour of climate system (CO 2) Reprinted by permission from Macmillan Publishers Ltd : Paillard, D. , The timing of Pleistocene glaciations from a simple multiple-state climate model. Nature, v. 391. p. 378 -381. Copyright (1998) Nature Publishing Group. Not under CC license. L 6 Themes: Quaternary glacial-interglacial cycles Explaining the “ 100 kyr world” 20
SOES 6047 - Global Climate Cycles � Shackleton (2000) de-convolved sea-level and temperature effects by subtracting ice core d 18 O records from marine benthic measurements � found that sea-level lagged temperature and CO 2 Figure 1. (A) Vostok air d 18 O record of (13), published time scale. (B) The "classic" Milankovitch forcing, June insolation at 65°N. (C) Benthic d 18 O record of core V 1930 (18), published time scale. All figures From: Shackleton, N J. , (2000) The 100, 000 -year ice-age cycle identified and found to lag temperature, carbon dioxide, and orbital eccentricity. Science. v. 289, no. 5486, p. 1897 -1902. Reprinted with permission from AAAS. This figure may be used for non-commercial, classroom purposes only. Any other uses requires the prior written permission from AAAS. Original benthic data from: Shackleton, N. J. & Pisias, N. G. , ‘Atmospheric carbon dioxide, orbital forcing, and climate’, in: The Carbon Cycle and Atmospheric CO: Natural Variations Archean to Present, T. S. Sundquist & W. S. Broecker, eds. (American Geophysical Union), Washington, D. C. , (1985), Geophysical Monograph Series 32, p 412– 417. L 6 Themes: Quaternary glacial-interglacial cycles Comparing marine and ice data 21
SOES 6047 - Global Climate Cycles � New benthic stacks produced by Karner et al. (2002) � “minimally tuned” Reproduced by permission of American Geophysical Union: Karner, D. B. , Levine, J. , Medeiros, B. P. , Muller, R. A. , Constructing a stacked benthic d 18 O record’, Paleoceanography. v. 17, p. 1030. 20 July 2002, Copyright [2002] American Geophysical Union. L 6 Themes: Quaternary glacial-interglacial cycles Newest stacks 22
SOES 6047 - Global Climate Cycles � New benthic stacks produced by Lisiecki & Raymo (2005) � better adjusted records, extend to 5 Ma Reproduced by permission of American Geophysical Union: Lisiecki & Raymo A Pliocene-Pleistocene stack of 57 globally distributed benthic d 18 O records, Paleoceanography, v. 20, PA 1003. 18 January 2005. Copyright [2005] by the American Geophysical Union. Reproduced by permission of American Geophysical Union. L 6 Themes: Quaternary glacial-interglacial cycles Newest stacks 23
24 SOES 6047 - Global Climate Cycles � Thompson & Goldstein (2005) produced very well dated sealevel record from globally distributed coral measurements � shows beautiful NOAA National Marine Sanctuary From: Lambeck, K, Chappell, J. , (2001) Sea level Change through the Last Glacial Cycle. Science, v. 292, no. 5517, p. 679 -686. Reprinted with permission from AAAS. This figure may be used for non-commercial, classroom purposes only. Any other uses requires the prior written permission from AAAS. From: Henderson, G. M. , (2005) Coral Clues to Rapid Sea-Level Change. Science, v. 308, no. 5720, p. 361 -362. Reprinted with permission from AAAS. This figure may be used for non-commercial, classroom purposes only. Any other uses requires the prior written permission from AAAS. L 6 Themes: Quaternary glacial-interglacial cycles Coral sea-level records
25 SOES 6047 - Global Climate Cycles � High-resolution benthic isotope records from pre-Quaternary times have recently become available. � They show a very different pattern compared to the 100 kyr and 41 kyr world of the Plio-Pleistocene � much stronger 400 kyr cycle in the Mio/Oligocene L 6 Themes: Quaternary glacial-interglacial cycles Are quaternary glacial cycles unusual? � Zachos et al. , Science (2001 a) From: Zachos, J. C. , Pagani, M. , Sloan, L. , Thomas, E. , Billups, K. , (2001) ‘Trends, rhythms, and aberrations in global climate 65 Ma to present’, Science, v. 292, p. 686– 693. Reprinted with permission from AAAS. This figure may be used for non-commercial, classroom purposes only. Any other uses requires the prior written permission from AAAS.
SOES 6047 - Global Climate Cycles � Remember the very strong correlation of temperature and CO 2 from icecore records (Petit et al. , 1999, Lect 5) � how exactly are they related, and what is their relative timing? � At least part of the answer: carbonate chemistry of oceans (read Chapter 9 of Broecker & Peng for some older ideas) L 6 Themes: Quaternary glacial-interglacial cycles Glacial-interglacial CO 2 cycles 26 Reproduced with permission of Macmillan Publishers Ltd: Petit, J. R. , Jouzel, J. , Raynaud, D. , Barkov, N. I. , Barnola, J. -M. , Basile, I. , Bender, M. , Chappellaz, J. , Davis, M. , Delaygue, G. , Delmotte, M. , Kotlyakov, V. M. , Legrand, M. , Lipenkov, V. Y. , Lorius, C. , PÉpin, L. , Ritz, C. , Saltzman E. , Stievenard, M. , (1999) Climate and atmospheric history of the past 420, 000 years from the Vostok ice core, Antarctica. Nature v. 399, p 429 -436. Copyright (1999). Not under CC licence. � main observation: glacial p. CO 2 = 200 ppm, interglacial ca 270 � Problem: it is very hard to explain the difference of 70 ppm in terms of PROCESSES. . . the following slides courtesy of Andy Ridgwell, illustrating the various competing effects of raising and lowering CO 2
SOES 6047 - Global Climate Cycles Courtesy of Dr. Andy Ridgwell, University of Bristol, UK. L 6 Themes: Quaternary glacial-interglacial cycles G-IG changes in CO 2 27
SOES 6047 - Global Climate Cycles Courtesy of Dr. Andy Ridgwell, University of Bristol, UK. L 6 Themes: Quaternary glacial-interglacial cycles G-IG changes in CO 2 28
SOES 6047 - Global Climate Cycles Courtesy of Dr. Andy Ridgwell, University of Bristol, UK. L 6 Themes: Quaternary glacial-interglacial cycles G-IG changes in CO 2 29
SOES 6047 - Global Climate Cycles Courtesy of Dr. Andy Ridgwell, University of Bristol, UK. L 6 Themes: Quaternary glacial-interglacial cycles G-IG changes in CO 2 30
SOES 6047 - Global Climate Cycles Courtesy of Dr. Andy Ridgwell, University of Bristol, UK. L 6 Themes: Quaternary glacial-interglacial cycles G-IG changes in CO 2 31
SOES 6047 - Global Climate Cycles Courtesy of Dr. Andy Ridgwell, University of Bristol, UK. L 6 Themes: Quaternary glacial-interglacial cycles G-IG changes in CO 2 32
SOES 6047 - Global Climate Cycles Courtesy of Dr. Andy Ridgwell, University of Bristol, UK. L 6 Themes: Quaternary glacial-interglacial cycles G-IG changes in CO 2 33
SOES 6047 - Global Climate Cycles Courtesy of Dr. Andy Ridgwell, University of Bristol, UK. L 6 Themes: Quaternary glacial-interglacial cycles G-IG changes in CO 2 34
SOES 6047 - Global Climate Cycles Courtesy of Dr. Andy Ridgwell, University of Bristol, UK. L 6 Themes: Quaternary glacial-interglacial cycles G-IG changes in CO 2 35
SOES 6047 - Global Climate Cycles Courtesy of Dr. Andy Ridgwell, University of Bristol, UK. L 6 Themes: Quaternary glacial-interglacial cycles G-IG changes in CO 2 36
SOES 6047 - Global Climate Cycles Courtesy of Dr. Andy Ridgwell, University of Bristol, UK. L 6 Themes: Quaternary glacial-interglacial cycles G-IG changes in CO 2 37
SOES 6047 - Global Climate Cycles Courtesy of Dr. Andy Ridgwell, University of Bristol, UK. L 6 Themes: Quaternary glacial-interglacial cycles G-IG changes in CO 2 38
SOES 6047 - Global Climate Cycles Courtesy of Dr. Andy Ridgwell, University of Bristol, UK. L 6 Themes: Quaternary glacial-interglacial cycles G-IG changes in CO 2 39
SOES 6047 - Global Climate Cycles Courtesy of Dr. Andy Ridgwell, University of Bristol, UK. L 6 Themes: Quaternary glacial-interglacial cycles G-IG changes in CO 2 40
SOES 6047 - Global Climate Cycles Courtesy of Dr. Andy Ridgwell, University of Bristol, UK. L 6 Themes: Quaternary glacial-interglacial cycles G-IG changes in CO 2 41
SOES 6047 - Global Climate Cycles Courtesy of Dr. Andy Ridgwell, University of Bristol, UK. L 6 Themes: Quaternary glacial-interglacial cycles G-IG changes in CO 2 42
SOES 6047 - Global Climate Cycles Despite best efforts, still need to explain 110 ppm residual ! will come back to this in later lecture Courtesy of Dr. Andy Ridgwell, University of Bristol, UK. L 6 Themes: Quaternary glacial-interglacial cycles G-IG changes in CO 2 43
44 SOES 6047 - Global Climate Cycles � New IPCC 2007 summary for policy makers released: http: //www. ipcc. ch/SPM 2 feb 07. pdf � BUT: some view this as too conservative (Rahmstorf, Science, 2007 a): Both figures from: Rahmstorf, S. , (2007 a). A semi-empirical approach to projecting future sea-level rise. Science. v. 315, p. 368 -370. Reprinted with permission from AAAS. These figures may be used for non-commercial, classroom purposes only. Any other uses require the prior written permission from AAAS. L 6 Themes: Quaternary glacial-interglacial cycles Recent news:
SOES 6047 - Global Climate Cycles � Rahmstorf et al. (Science 2007 b) also compared the prediction of the last IPCC report with actual measurements since. � He observed that the actual change was larger than predicted: From: Rahmstorf, S. , Cazenave, A. , Church, J. A. , Hansen, J. E. , Keeling, R. F. , Parker, D. E. , Somerville R. C. J. , (2007 b) Recent Climate Observations Compared to Projections. Science v. 316, p. 709. Reprinted with permission from AAAS. This figure may be used for non-commercial, classroom purposes only. Any other uses require the prior written permission from AAAS. L 6 Themes: Quaternary glacial-interglacial cycles Recent news (2): 45
SOES 6047 - Global Climate Cycles � The Plio-Pleistocene is characterised by global large fluctuations in glacial extent � These fluctuations occur in many data: benthic, planktonic, marine, terrestrial � From ice-core data, we know that they are also reflected in temperature proxies and CO 2 � During the past ~800 kyr, they are dominated by a ca. 100 kyr sea-saw pattern, before by a more regular 41 kyr oscillation � The glacial-interglacial cycles, though disputed, have been correlated to astronomical forcing terms, which pace the cycles in a semi-regular fashion � There is still on-going research as to why the system changed from a 100 kyr to a 41 kyr world � In older parts of the geological history glacial cycles occur on different time-scales, and with different expressions � We still do not understand in detail what processes interact to generate the consisten variations of CO 2 (80 ppm) L 6 Themes: Quaternary glacial-interglacial cycles Key point summary 46
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