Globaler Klimawandel: Ursachen und Folgen

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1 Globaler Klimawandel: Ursachen und Folgen Dr. Axel Kleidon Max-Planck-Institut für Biogeochemie Übersicht Datum Thema Einführung, Überblick über das Klimasystem Strahlung und Energiebilanz Dynamik der Atmosphäre und Ozeane fällt aus Wasser- und Kohlenstoffkreislauf Klimate der Erde Modelle, Wechselwirkungen und Feedbacks Paleoklimatologie Eiszeiten, Holozän, die letzten 1000 Jahre Global Warming: Szenarios der nächsten 100 Jahre Schillertag Global Warming: Konsequenzen Andere Formen von Klimaänderung: Landnutzung, Urbanisierung Zusammenfassung, Diskussion, Feedback 1 2 Zusammenfassung Klimamodelle Feedbacks (positiv/negativ) Multiple Steady States Overview How do we know about past climate change? (dating and sources of information) Causes for climatic change Early Earth 3 4

2 Multiple Steady States Ice-Albedo Feedback as snow extent and surface albedo depend on surface temperature I0/4 (1 - ap) -! T 4 = 0 Ts surface temperature depends on surface albedo Surface Albedo as Ts = g(as) 3 possible solutions to the steady-state energy balance as = f(ts) Surface Temperature Ts Ts as Budyko Budyko Water Cycling Feedback More Multiple Steady States Biomass B Precipitation P P = g(b) B = f(p) multiple solutions to the steady-state carbon/water balance water cycling feedback: West Africa Claussen, Brovkin et al, Zeng and Neelin, Wang and Eltahir, Zeng et al. boreal forest feedback: consequences: Levis et al., Brovkin et al., Kubatzki and Claussen solution depends on initial conditions possible catastrophic shift to changing conditions after Brovkin et al. (1998) and Wang (2004) 7 8

3 Paleoclimatology Dating the Past Use of Isotopes: Isotopes: same chemical element, but different weight. Examples: H 2O (water): normal molecular weights: H-1, O-16 variants: D (H-2); O-18 CO 2 (carbon dioxide): normal molecular weights: C-12, O-16 variants: C-13; C Dating the Past Radioactive isotopes as timers : Concentration Time daughter isotope radioactive isotope Dating the Past Radioactive isotopes as timers : Example: Radiocarbon (C-14) is radioactive, i.e. decays exponentially with half life of 5730 years normally created in upper atmosphere once organic material is buried, C-14 decays 11 12

4 Reconstructing the Past Use of Isotopes: Estimating ages Example: Radiocarbon (C-14)! - is radioactive, i.e. decays exponentially with half life of 5730 years " - normally created in upper atmosphere " - once organic material is buried, C-14 decays Parent Isotope Dating the Past Daughter Isotope Half-Life Useful for ages: Useful for dating: Rubidium-87 Strontium Byr 100 Myr Granites Uranium-238 Lead Byr >100 Myr Many rocks Uranium-235 Lead Byr >100 Myr Many rocks Potassium 40 Argon Byr >100,000 yr Basalts Thorium-230 Radon ,000 yr < 400,000 yr Corals Carbon-14 Nitrogen-14 5,780 yr < 50,000 yr anything with carbon Source: Ruddiman Earth s climate Dating the Past Use of Isotopes: Understanding processes Example: O-18 stable isotope leads to heavier water affects mass-dependent processes, e.g. evaporation e.g. colder climate => more ice, less sea-water => sea-water contains more O-18 => deposits contain more O-18 Dating the Past Use of Isotopes: Understanding processes Example: O-18! - stable isotope " - leads to heavier water " - affects mass-dependent processes, e.g. evaporation " - e.g. colder climate " " -> more ice, less sea-water " " -> sea-water contains more O-18 " " -> deposits contain more O

5 Information from the Past Ice core records instrumental historical tree rings ice cores, lake sediments, corals ocean sediments # 100 years # 1000 years # 10,000 years # 100,000 years # 10,000,000 years * * * * * * * * ** *** ** * **** * glacier snow accumulates at top of glacier, carrying specific isotopic composition layers of dust, ash from volcanic eruptions little air pockets that contain past atmospheric composition Ice core records Ice core record from Vostok, Antarctica 19 Petit Globaler et Klimawandel: al. (1999) Nature Ursachen und Folgen Kleidon SS

6 Ice core records Information from the Past climate resolutions of sediment records: Continental Lakes Coastal Oceans Deep ocean typical sediment influx rate 1 mm/yr 10cm-1m/1000 yr 1 cm/yr typical depth of mixing 1-10 cm 10cm - 1m 1-10cm typical resolvable detail yrs yrs yrs Ruddiman Earth s Climate Pollen records Pollen records oak sedge pine when flowering, tree disperses pollen pollen fall into nearby lake and settle down sunflower lake sediment contains accumulated deposits of pollen of certain species

7 Colinvaux et al. (1996) Science Pollen records Globaler Colinvaux Klimawandel: et al. (1996) Ursachen Science und Folgen Kleidon SS Ocean cores planktonic foraminifera when plankton in surface ocean dies, it settles down to deep ocean ocean sediment accumulate deposits of shells, also dust ocean 27 28

8 The Paleoclimatic Record: Ocean cores Globaler Klimawandel: Ursachen und Folgen Kleidon SS Globaler Klimawandel: Ursachen und Folgen 29 The Paleoclimatic Record: Ocean cores Globaler Klimawandel: Ursachen und Folgen Kleidon SS Kleidon SS The Paleoclimatic Record: Ocean cores Globaler Klimawandel: Ursachen und Folgen Kleidon SS

9 The Paleoclimatic Record: Ocean cores The Paleoclimatic Record: Ocean cores Tree rings Tree rings The Paleoclimatic Record: Tree Rings growing conditions affect tree growth thickness of growth reflects limitations (temperature or moisture availability) no limitations => no tree rings Dendrochronology 35 36

10 Tree rings Coral records each year, corals add thin layer contains information of isotopic composition (CaCO3) Other records signs of glaciations on rocks magnetism distribution of taxa rock types: e.g. signs of oxidization Early Earth: hot or cold? Lineweavber and Schwartzman (2005) 39 40

11 Causes for Climatic Change 1. external: 2. internal: solar luminosity orbital characteristics plate tectonics greenhouse effect extent of snow/glaciers/ice sheets memory, multiple stable states Lineweaver & Schwartzman (in press) Cosmic Thermobiology Causes for Climatic Change Long-term changes: increase in solar luminosity changes in atmospheric composition: greenhouse gases, in particular CO2 oxygen plate tectonics: distribution of land masses position of ocean passages rock weathering rates Causes for Climatic Change Present-day Carbon reservoirs: carbon stores in GtC atmosphere 760 living biomass (land) 610 dissolved CO2 (ocean) 740 carbonate (ocean) 1,300 soils (land) 1,600 fossil fuels 4,300 bicarbonate (ocean) 37,000 organic carbon in sedimentary rocks 10,000,000 limestone 40,000,

12 Feedbacks and Earth History runaway greenhouse ice-albedo feedback silicate rock weathering Geologic Carbon Cycle Figure 3 Diagram illustrating the modern carbonate-silicate cycle, also referred to as the inorganic carbon cycle