The Global Carbon Cycle

Transcription

1 The Global Carbon Cycle Laurent Bopp LSCE, Paris 1 From NASA Website

2 Introduction CO2 is an important greenhouse gas Contribution to Natural Greenhouse Effect Contribution to Anthropogenic Effect 2

3 Altitude Introduction: CO 2 and the saturation myth Isn t it already so much CO 2 in the air that its effect on infrared radiation is "saturated? Isn t water vapor already blocking all the infrared rays that CO 2 ever would? Radiation emitted to space Absorption - emission by gases Temperature Emitted Radiation from the surface 3

4 Introduction: CO 2 and the saturation myth Isn t it already so much CO 2 in the air that its effect on infrared radiation is "saturated? Isn t water vapor already blocking all the infrared rays that CO 2 ever would? Simple arguments as proposed by Weart & Pierrehumbert on RealClimate. (a) You d still get an increase in greenhouse warming even if the atmosphere were saturated, because it s the absorption in the thin upper atmosphere (which is unsaturated) that counts (b) It s not even true that the atmosphere is actually saturated with respect to absorption by CO 2, (c) Water vapor doesn t overwhelm the effects of CO 2 because there s little water vapor in the high, cold regions from which infrared escapes, (d) These issues were satisfactorily addressed by physicists 50 years ago, and the necessary physics is included in all climate models. 4

5 Introduction Past and recent variations of atmospheric CO2 5

6 Introduction CO 2 and Climate have varied in phase 6 IPCC, 2007

7 Introduction 7 IPCC, 2007

8 Introduction EPICA, Dome C (jusqu à 800 ka) IPCC,

9 Introduction CO2 concentration in the atmosphere seems to vary over very different time-scales from season to millions of years These variations are explained by the exchange with different reservoirs rocks, ocean, soil, biosphere and imply some very different processes volcanism, weathering, dissolution, chemistry, photosynthesis, respiration The carbon cycles Long Term Carbon Cycle & Short Term Carbon Cycle 9

10 DaveSTELLA/Carbon/long_term_carbon.htm#schem atic Short-Term Carbon Cycle From Sarmiento and Gruber,

11 +1,5 o C Today s Focus Short term carbon cycle (season to century) impacted by the release of long-term carbon reservoirs 1100 pp 550 pp +6,0 o Atmospheric pco2 (ppm) 280 ppm 370 ppm Surface Temperature ( o C) +0,6 o C

12 Outline 1. Anthropogenic Sources of CO2 2. Observations, Trends and Budgets 3. Terrestrial and Marine Carbon Cycle : major processes 4. Coupling of the carbon cycle and the climate system 12

13 1. Anthropogenic Sources of CO2 13

14 1. Anthropogenic Sources of CO2 Fossil Fuel CO 2 Emissions CO 2 emissions (Pg C y -1 ) Growth rate % per year Growth rate % per year CO 2 emissions (Pg CO 2 y -1 ) 2009: Emissions:8.4±0.5 PgC Growth rate: -1.3% 1990 level: +37% Growth rate: +3.2% 2010 (projected): Growth rate: >3% Time (y) Friedlingstein et al. 2010, Nature Geoscience; Gregg Marland, Thomas Boden-CDIAC

15 Factor (relative to 1990) 1. Anthropogenic Sources of CO2 Kaya Identity : Emissions = P x W x C World F Emissions (emissions) P Population (population) g Wealth = G/P = per capita GDP 0.6 h Carbon = F/G intensity of GDP Raupach et al 2007, PNAS 15

16 Carbon Emissions per year (C tons x 1,000,000) Fossil Fuel CO 2 Emissions: Top Emitters China USA Russian Fed. Japan India Time (y) Global Carbon Project 2010; Data: Gregg Marland, Tom Boden-CDIAC

17 Total Carbon Emissions (tons x 1,000,000) Top 20 CO 2 Emitters & Per Capita Emissions Per Capita Emissions (tons C person y -1 ) Global Carbon Project 2010; Data: Gregg Marland, Thomas Boden-CDIAC 2010; Population World Bank

18 CO 2 Emissions by Fossil Fuel Type CO 2 emissions (PgC y -1 ) 4 40% 3 Oil 36% Coal 2 Gas 1 Cement Time (y) Updated from Le Quéré et al. 2009, Nature Geoscience; Data: Gregg Marland, Thomas Boden-CDIAC

19 Fossil Fuel Emissions: Actual vs. IPCC Scenarios Fossil Fuel Emission (PgCy -1 ) Observed Projected A1B Models Average A1FI Models Average A1T Models Average A2 Models Average B1 Models Average B2 Models Average Full range of IPCC individual scenarios used for climate projections Time (y) Updated from Raupach et al. 2007, PNAS; Data: Gregg Marland, Thomas Boden-CDIAC 2010; International Monetary Fund

20 1. Anthropogenic Sources of CO2 100% 80% Least Developed Countries Developing Countries 60% 40% 20% 0% Cumulative Emissions [ ] Flux in 2004 Flux Growth in 2004 Population in 2004 India China FSU Japan EU USA D1 Raupach et al. 2007, PNAS 20

21 CO 2 Emissions from FF and LUC ( ) CO 2 emissions (PgC y -1 ) Fossil fuel Land use change LUC emissions now ~10% of total CO 2 emissions Time (y) Updated from Le Quéré et al. 2009, Nature Geoscience 21

22 CO 2 Emissions from Land Use Change CO 2 emissions (PgC y -1 ) ±0.7 PgCy ±0.7 PgCy -1 CO 2 emissions (PgCO 2 y -1 ) 1990s Emissions: 1.5±0.7 PgC Emissions: 1.3±0.7 PgC : Emissions: 0.9±0.7 PgC Time (y) Friedlingstein et al. 2010, Nature Geoscience; Data: RA Houghton, GFRA

23 Sink Source 1. Anthropogenic Sources of CO2 : Deforestation But very large uncertainties. New estimate based on remote sensing (de Fries et al. 2002) : GtC/yr for 90s 23

24 2. Observations, Trends and Budget 24

25 2. Observations, Trends and Budget 25

26 November 2010 Parts Per Million (ppm) 2. Observations, Trends and Budget GLOBAL MONTHLY MEAN CO 2 December 2009: ppm September 2010 (preliminary): ppm 39% above pre-industrial : 1.3 ppm y : 1.6 ppm y : 1.5 ppm y : 1.9 ppm y -1 Data Source: Pieter Tans and Thomas Conway, 2010, NOAA/ESRL Annual Mea Growth Rate (ppm y -1 )

27 2. Observations, Trends and Budget Point Barrow (Alaska) - Maunoa Loa (Hawai) - South Pole 27

28 2. Observations, Trends and Budget : Global Network 28

29 2. Observations, Trends and Budget 29

30 2. Observations, Trends and Budget Sinks of Carbon 30

31 Ocean sink (PgCy -1 ) 5 models Land sink (PgCy -1 ) 5 models 2. Observations, Trends and Budget 2 Modelled Natural CO 2 Sinks Time (y) Updated from Le Quéré et al. 2009, Nature Geoscience 31

32 2. Observations, Trends and Budget Use of O2 atm. observations to constrain the carbon cycle (Keeling and Shertz, 1992) CO 2 O 2 ATMOSPHERE CO 2 à Mauna Loa (Keeling C.D) O 2 /N 2 à Cape Grim et La Jolla (Bender - Keeling R.F) 32

33 2. Observations, Trends and BudgetC Use of O2 atm. observations to constrain the carbon cycle (Keeling and Shertz, 1992) July 1991 CO 2 = FF - Cont. - Ocean O 2 = a FF - b Cont FF Combustion Observations July 1998 Jan July 1999 A CONTINENT B OCEAN CO 2 (ppm) 33

34 2. Observations, Trends and BudgetC Carbon Budget (1980s, 1990s, ) 34

35 2. Observations, Trends and Budget Atmospheric Inversions to estimate regional fluxes Direct Approach 3D Transport Model Concentrations Flux observations Inversion 35

36 2. Observations, Trends and Budget Atmospheric Inversions to estimate regional fluxes Gurney et al. Transcom Project 36

37 2. Observations, Trends and Budget : Oceanic Observations CO2 fluxes from oceanographic measurements (around 3million) (Takahashi et al.) 37

38 Ocean Estimations vs Inversions 38 Peylin et al.

39 2. Observations, Atlantic Trends and Budget : Oceanic Observations Anthropogenic Carbon in the Ocean (Sabine et al. 2004) Pacific Indian Total anthropogenic Carbon : PgC in

40 2. Observations, Trends and Budget : Land Observations Ecosystems Estimations (based on Statistics) vs Inversions Jansen et al

41 3. Terrestrial and Marine Carbon Cycle : major processes 3.1 Terrestrial Processes 41

42 Which processes are responsible for the terrestrial sink? CO2 fertilization Anthropogenic nitrogen deposition Climatic Variability Land-use changes 42

43 3. Terrestrial and Marine Carbon Cycle : major processes 3.2 Marine Processes Données Carbon Sink Carbon Source (Takahashi et al. 2009) 44

44 3. Terrestrial and Marine Carbon Cycle : major processes 3.2 Marine Processes Marine Carbon Cycle : Physics / Chemistry / Biology 45

45 3. Terrestrial and Marine Carbon Cycle : major processes 3.2 Marine Processes Marine Carbon Cycle : Physics / Chemistry / Biology 46

46 Chemistry 47

47 Chemistry DIC = CO 2 + HCO CO 2-3 Alkalinity (carbonate) = HCO * CO 2-3 Theoritically, if you know 2 out of (ph, DIC, Alk, CO2, HCO3-, CO32-),. In model : DIC and Alkalinity only represented In the field : DIC, Alk, pco 2 are measured 48

48 Saturation of the Sink Revelle Factor : R = (dpco 2 /ddic)/(pco 2 /DIC) It describes how the partial pressure of CO 2 in seawater (pco 2 ) changes for a given change in DIC (Revelle and Suess, 1957). 49

49 Ocean s acidification Feely et al. 2004, Science Saturation Horizon for Calcite and Aragonite Mean ph :

50 Solubility Pump Dissolution in cold waters of high latitudes Transfer via ocean circulation Release in warm or upwelling regions Time constants gas exchange ~ 6 month for a MLD of 40m transport in the ocean : up to 1000 yr 51

51 Biological Pumps C-fixation in the euphotic layer (photosynthesis & calcification) Most part is recycled Some part is exported beneath (export production of OM and CaCO 3 ) Soft-Tissue Pump Carbonate Pump 52

52 Integration Impact of different processes on surface pco 2, DIC and Alk: 53

53 Integration Impact of the different pumps on the vertical distribution of DIC Solubility: 10% Soft-Tissue: 70% Carbonate: 20% (based on vertical profiles of PO4, Alk, DIC) 54

54 Integration Impact of different processes on surface pco 2, DIC and Alk: Seasonal Cycle at mid-high lat.: Compensating Effects: Solubility Mixing Biology Summer / WInter low amplitude of the seasonal cycle (if you compare to O 2 for example : all in the same direction!) 55

55 Which processes are responsible for today s marine sink? 58

56 Which processes are responsible for today s marine sink? «Despite the importance of biological processes for the ocean s natural cycle, current thinking maintains that the oceanic uptake of anthropogenic CO2 is primarily a physically and chemically controlled process surimposed on a biogically driven carbon cycle that is close to steady state» (IPCC, 2001) 59

57 4. Carbon-Climate Coupling in the 21 st century Emissions Carbon Sinks Concentrations Climate 60 (IPCC, 2007)

58 4. Carbon-Climate Coupling in the 21 st century 4.1 Evidence from observations? Southern Ocean Carbon Fluxes Le Quéré et al

59 Airborne Fraction 4. Carbon-Climate Coupling in the 21 st century Evidence from observations? 1.0 Trend: 0.31 % y -1 (p=~0.9) % % Time (y) Airborne fraction : Fraction of emitted CO2 that stays in the atmosphere Canadell et al. 2007, PNAS, in press 62

60 4. Carbon-Climate Coupling in the 21 st century 4.2 Projections Mechanisms «Amazon die-back» ppm en 2100! 63

61 4. Carbon-Climate Coupling in the 21 st century 4.2 Projections - 11 coupled climate-carbon models (Friedlingstein et al. 2006) - all show a positive feedback - but large uncertainties on this feedback (+20 to +220 ppm in 2100!) 64

62 4. Carbon-Climate Coupling in the 21 st century Changes in Ocean and Land uptake are function of atm. pco2 and climate 65

63 4. Carbon-Climate Coupling in the 21 st century Which processes are responsible (in the models) for the climate impact on uptakes? Land NPP decreases with decreasing water availability Heterotrophic respiration increases to temperature Ocean -> But no consensus. Large uncertainties Warming Effect : Increased T decrease CO2 solubility Dynamical Effect : Increases stratification prevents anth. CO2 penetration Biological Effects? -> Uncertainties on the dynamical effect. 66

64 4. Carbon-Climate Coupling in the 21 st century Important consequences for our future climate 67 IPCC, 2007