Long-lived non-co 2 Greenhouse Gases. Ingeborg Levin Institut für Umweltphysik, University of Heidelberg Ingeborg.Levin@iup.uni-heidelberg.

Transcription

1 Long-lived non-co 2 Greenhouse Gases Ingeborg Levin Institut für Umweltphysik, University of Heidelberg Ingeborg.Levin@iup.uni-heidelberg.de

2 Topics to be discussed: Sources, sinks and global distribution of methane (CH 4 ) and nitrous oxide (N 2 O) in the troposphere and stratosphere Isotopes in the global methane budget CFCs, and their substitutes (HCFCs and HFCs) (Sulfur Hexafluoride and its recent changes, estimates of its global emissions)

3 Greenhouse Gases IR absorption in the atmosphere 0 km 5800 K 255 K Absorption [%] 11 km CH 4 N 2 O O 2 + O 3 CO 2 H 2 O [Peixoto and Oort, 1993] wavelength (μm)

4 Greenhouse Gases absorption in the atmosphere Atmospheric window Absorption (%) also Ozone Depleting Substances (ODS) and their substitutes have absorption bands in the atmospheric window [Peixoto and Oort, 1993]

5 Anthropogenic Sum GHGs emissions since 1980 CO 2 -equivalent on a 100-yr time horizon: e.g. the GWP of 100 Tg CH Pg CO 2 1Tg= g, 1Pg= g = kg = 1 Gt Anthropogenic emissions (Pg CO 2 -eq. yr -1 ) CO 2 (fossil & land use) CO 2 (fossil) Sum Non-CO 2 GHGs CH 4 Ozone depl. subst. N 2 O HFCs [Montzka et al., 2011]

6 Methane [ppb] Atmospheric CH 4 increase (in the Southern Hemisphere) 1750 CH 4 Southern Hemisphere NOAA/CMDL Neumayer Greenland Ice [Blunier et al., 1993] Antarctic Ice [Etheridge et al., 1992] mean southern hemisphere [NOAA/GMD] atmosphere Neumayer, Antarctica YEAR 1 ppb CH 4 = 1 CH 4 molecule per 10 9 air molecules

7 Ice cores as archives to measure the atmospheric trace gas composition of the past Dome C [curtesy D. Wagenbach]

8 Methane [ppb] Atmospheric CH 4 increase (in the Southern Hemisphere) 1750 CH 4 Southern Hemisphere NOAA/CMDL Neumayer Greenland Ice [Blunier et al., 1993] Antarctic Ice [Etheridge et al., 1992] mean southern hemisphere [NOAA/GMD] atmosphere Neumayer, Antarctica YEAR 1 ppb CH 4 = 1 CH 4 molecule per 10 9 air molecules

9 Run by: Alfred-Wegener Institut für Polarforschung co-op. with Rolf Weller Antarctic station Neumayer 70ºS

10 Arctic station Alert, Nunavut, Canada 82ºN Run by: Meteorological Service of Canada co-op. with: Douglas Worthy

11 Long-term trend of CH 4 in polar regions CH 4 [ppb NOAA2004] 1950 Alert integrated Alert flasks Neumayer cylinders Neumayer flasks Alert (82 N) Neumayer (71 S) YEAR [Heidelberg unpublished data]

12 The atmospheric monitoring network of NOAA/ESRL [

13 Global Distribution of CH 4 in the marine Troposphere [

14 Production of methane * Microbes (methanogens) produce methane under anaerobic conditions by Acetate fermentation CH 3 COOH CH 4 + CO 2 and by reduction of carbon dioxide CO 2 + 4H 2 CH 4 + 2H 2 O * Thermogenic and pyrogetic processes (e.g. incomplete combustion during biomass burning) produce also CH 4 (and CO, CO 2 )

15 Sources and sinks of tropospheric methane Tropospheric Quellen [ Tg / Sources yr ] [Tg/yr] Rice cultivation Reisfelder Biomassen Biomass Verbrennung burning Natürliche Natural sources Quellen Wiederkäuer Vertebrates Mülldeponien Waste deposits Energy Energieproduction [IPCC, 2001]

16 Direct measurements on CH 4 sources Bog in Russia [Neumann, 1999]

17 Direct measurements on CH 4 sources Measurements with Flux Chambers Tonne 1 (slope) Tonne 2 (hollow) Mittelwerte Tonne 1 und 2 Tonne 3 (hummock) Mittelwert Tonne show large heterogeneity CH 4 -Fluß [mmol/m 2 h] [Neumann, 1999] Datum

18 Processes influencing CH 4 emissions from wetlands [Wania, 2007]

19 Ozone depletion Destruction of CH 4 by OH radicals Ozone production O 3 + hν O 2 + O* O* + H 2 O 2 OH (τ 1 sec.) CH 3 CCl 3 (Methylchloroform): Tracer for the global distribution of OH (ca radicals per cm 3 ) since its sources are well known, sink via OH [Crutzen et al., 1999]

20 Sources and sinks of tropospheric methane Tropospheric Quellen [ Tg / Sources yr ] Tropospheric Senken [Tg Sinks / yr] [Tg/yr] [Tg/yr] Biomassen Biomass Verbrennung burning Natürliche Natural sources Quellen Transport to in Stratosphäre Stratosphere Oxidation in soils Böden Oxidation in Rice cultivation Reisfelder Wiederkäuer Vertebrates Mülldeponien Waste deposits Energy Energieproduction troposphärisches OH Tropospheric OH and Cl [IPCC, 2001] tropospheric life time ca. 10 years

21 What are the causes of the changing trends and inter-annual variations? [IPCC AR5, 2013; data from UCI, AGAGE, NOAA/ESRL/GMD]

22 Temporal development of the global OH sink [Montzka et al., Science 2011]

23 Processes influencing CH 4 emissions from wetlands [Wania, 2007]

24 Isotopes in CH 4 stable: radioactive 12 C: 1 14 C: C: 1.1 % half life = 5700 years 1 H: 1 3 H: H (D): % half life = years

25 δ Notation δ = R Sample R R Stan dard Stan dard 1000 [ ] 18 O = O R 2 H 2 1 H 13 C 13 D = = R = R 12 H C δ 18 O and δd Standard is ocean water: Vienna Standard Mean Ocean Water (V-SMOW) δ 13 C Standard is a marine carbonate: Vienna Pee-Dee-Belemnite (V-PDB) [Mook, 2002]

26 Reasons for isotope fractionation: Molecules with larger mass and same kinetic energy (i.e. temperature) have - smaller velocity - smaller molecular diffusion coefficient - smaller collision frequency with other molecules - (normally) smaller reaction velocity Heavier molecules normally have - higher binding energy - smaller vapour pressure [Mook, 2002]

27 Stable isotopes in atmospheric CH 4 sources original plant material thermogenic &

28 Observed long-term trends of CH 4 and δ 13 CH CH 4 [ppb] Alert Barrow Izana Mauna Loa Baring H./C. Grim Antarctica global mean The higher CH 4 mole fraction at NH sites is associated with more depleted δ 13 CH 4 compared to SH sites δ 13 C-CH 4 [ vs VPDB] Antarctica Baring Head/ Cape Grim Mauna Loa Izana Alert Barrow global mean The long-term trend of δ 13 CH 4 since the 1980s to more enriched values indicates an increase of isotopically enriched CH 4 sources [modified from Levin et al., 2012]

29 1-Box model of the atmospheric methane budget Atmosphere -I CH4 (t)/τ I CH4 (t) i i di (t) i I (t) = Q (t) CH 4 CH 4 dt CH4 τ i Σ Q CH4 (t) i = 12 CH 4, 13 CH 4, 14 CH 4, 12 CH 3 D

30 Stable isotopes in atmospheric CH 4 sources thermogenic &

31 CH 4 budget changes [Kirschke et al., 2013]

32 Anthropogenic Sum GHGs emissions since 1980 CO 2 -equivalent on a 100-yr time horizon: e.g. the GWP of 100 Tg CH Pg CO 2 (1 Tg = g, 1 Pg = g) Anthropogenic emissions (Pg CO 2 -eq. yr -1 ) CO 2 (fossil & land use) CO 2 (fossil) Sum Non-CO 2 GHGs CH 4 Ozone depl. Subst. N 2 O HFCs [Montzka et al., 2011]

33 Tropospheric N 2 O increase (SH) N 2 O Southern Hemisphere N 2 O [ppb] Neumayer Cape Grim (ALEGAGE) ca. 20% Antarctic Ice [Machida et al., 1995] Atmosphere Neumayer, Antarctica Atmosphere Cape Grim (ALE GAGE) YEAR 1 ppb N 2 O = 1 N 2 O molecule per 10 9 air molecules

34 Tropospheric N 2 O in polar regions 325 N 2 O [ppb] Alert tanks Alert flasks Neumayer flasks YEAR [Heidelberg unpublished data]

35 Global distribution of tropospheric N 2 O observations [

36 Global tropospheric N 2 O budget Total natural: Total anthropogenic: ca g N yr -1 ca. 6.7± g N yr -1 [IPCC, 2001; 2007]

37 Distribution of total global N 2 O emissions [Hirsch et al., 2006]

38 Destruction of N 2 O Stratospheric UV photolysis (λ < 240 nm) Stratospheric oxidation by O( 1 D) possibly small soil sink Atmospheric lifetime 120 years

39 Balloon launching in Kiruna Courtesy K. Pfeilsticker

40 Kiruna, SF 6 [ppt] Druck [hpa] CO 2 [ppm] Greenhouse gases profiles in the Stratosphere CH 4 [ppb] N 2 O [ppb] [Heidelberg unpublished data]

41 Purely man-made long-lived GHGs

42 Anthropogenic Sum GHGs emissions since 1980 CO 2 -equivalent on a 100-yr time horizon: e.g. the GWP of 100 Tg CH Pg CO 2 (1 Tg = g, 1 Pg = g) Anthropogenic emissions (Pg CO 2 -eq. yr -1 ) CO 2 (fossil & land use) CO 2 (fossil) Sum Non-CO 2 GHGs CH 4 Ozone depl. Subst. N 2 O HFCs [Montzka et al., 2011]

43 Ozone Depleting Substances (ODS) banned under Montreal Protocol (1987+) Physically and chemically very stable, non-poisening Almost exclusively anthropogenic sources (e.g. F-11 = CFCl 3, F-12 = CF 2 Cl 2, F-113 = CFCl 2 CF 2 Cl), Used in industrial applications since ca as: Refrigerator gas (CFC-12) Aerosol dispersion gas (CFC-11 & CFC-12) Polyurethane foams (CFC-11) Solvents (CFC-11, CFC-113) Sinks: Photodissoziation by UV light (λ < 260 nm) Impacts: Ozone depletion in the stratosphere GHGs in the Troposphere

44 Trend of CFC-11 (τ Atm 45 yrs) in the last 30 years

45 Trend of CFC-12 (τ Atm 100 yrs) in the last 30 years

46 Trend of CH 3 CCl 3 (τ Atm 6 yrs) in the last 30 years

47 Anthropogenic Sum GHGs emissions since 1980 CO 2 -equivalent on a 100-yr time horizon: e.g. the GWP of 100 Tg CH Pg CO 2 (1 Tg = g, 1 Pg = g) Anthropogenic emissions (Pg CO 2 -eq. yr -1 ) CO 2 (fossil & land use) CO 2 (fossil) Sum Non-CO 2 GHGs CH 4 Ozone depl. Subst. N 2 O HFCs [Montzka et al., 2011]

48 HCFCs & HFCs: Substitutes for CFCs [Velders et al., 2009]

49 Development of CFCs, HCFCs & HFCs [IPCC, 2013]

50 Effect of Montreal Protocol and Perspectives PNAS Paper [Velders et al., 2009]

51 Sulphur Hexafluoride: SF 6 is a very stable man-made Greenhouse Gas Mean atmospheric lifetime: years Global Warming Potential: x CO 2 (100 yr time horizon) Kyoto - reported Atmospheric mole fraction today: 7 ppt (10-12 mol/mol) Sources of SF 6 : - ca. 75% from electrical applications - Magnesium industry - adiabatic applications Sinks of SF 6 : only in the Mesosphere > 60 km - UV Absorption (λ < 130 nm) - electron reactions

52 Global long-term trend of SF 6 in the troposphere SF 6 [ppt] 7 Alert 82 N (cylinders & flasks) Cherskii 69 N (flasks > 2500m) 6 Syktyvkar 61 N (flasks > 2500m) Rhine valley 48 N (flasks > 2500m) Izaña 28 N (cylinders) 5 Cape Grim 41 S (archive & flasks) Neumayer 71 S (cylinders) Neumayer 71 S (flasks) NH: Alert SH Neumayer Year Levin et al., 2010

53 Global long-term trend of SF 6 in the troposphere SF 6 [ppt] 7 Alert 82 N (cylinders & flasks) Cherskii 69 N (flasks > 2500m) 6 Syktyvkar 61 N (flasks > 2500m) Rhine valley 48 N (flasks > 2500m) Izaña 28 N (cylinders) 5 Cape Grim 41 S (archive & flasks) Neumayer 71 S (cylinders) Neumayer 71 S (flasks) NH: Alert SH Neumayer UNFCCC adopted growth rate [ppt yr -1 ] Year Levin et al., 2010

54 SF 6 emission estimates SF 6 emission [Gg/a] total this study (±1σ) total EDGAR Levin et al., 2010

55 Summary I CH 4 is the most abundant organic molecule in the atmosphere and produced mainly by anaerobic bacterial decomposition of organic material. Natural pyrogenic processes (biomass burning) contribute about 10%. The main destruction process of atmospheric CH 4 is via oxidation by OH in the troposphere with a mean atmospheric life time today of about 10 years. Anthropogenic CH 4 emissions are mainly from rice cultivation, cattle breeding, waste deposits and energy production and consumption. Atmospheric CH 4 has increased since pre-industrial times by more than a factor of two due to man-made emissions. Its short life time makes it a good candidate to reduce future climate change Inter-annual variations of global atmospheric CH 4 are not well understood but likely due to natural causes

56 Summary II N 2 O mole fraction has increased by about 20% since About 60% of N 2 O sources are natural, 40% are mainly associated to agricultural use of inorganic fertiliser and deposition of NOx from fossil fuels (increasing the availability of N in terrestrial and aquatic ecosystems). N 2 O has only negligible sinks in the troposphere and is destroyed in the stratosphere. Its mean life time is ca. 120 years Long-lived Ozone Depleting Substances - which are also strong GHGs - are currently decreasing due to largely reduced emissions after the Montreal Protocol; decrease rates depend on their atmospheric life times. CFC substitutes, HCFCs and HFCs are strongly increasing and if not reduced, will contribute up to 20% to global warming in 2050 SF 6 shows a continuing increase, accelerating in the last years, most likely due to the increasing energy demand in developing countries.

57 References Blunier, T. et al Atmospheric methane record from a Greenland ice core over the last 1000 years. Geophys. Res. Lett. 20, Crutzen, P. et al On the background photochemistry of tropospheric ozone. Tellus 51, Dlugokecky, E.J. et al., Global atmospheric methane: budget, changes and dangers. Phil. Trans. R. Soc. A 369, , doi: /rsta Etheridge, D.M. et al Changes in tropospheric methane between 1841 and 1978 from a high accumulation-rate Antarctic Ice Core. Tellus 44B, Hirsch, A. et al Inverse estimates of the global nitrous oxide surface flux from Global Biogeochem. Cycles 20, GB1008, doi: /2004gb IPCC, 2001; 2007; 2013, Climate Change 20xx. The Scientific Basis. Report of the Intergovernmental Panel on Climate Change ( Kirschke, S. et al., Three decades of global methane sources and sinks, Nature Geoscience 6, Levin, I. et al., The global SF6 source inferred from long-term high precision atmospheric measurements and its comparison with emission inventories. Atmos. Chem. Phys. 10, Levin, I. et al., No inter-hemispheric δ 13 CH 4 trend observed. Nature 486, Montzka, S. A., et al Non-CO2 greenhouse gases and climate change. Nature 476, doi Montzka, S.A. et al., Small Interannual Variability of Global Atmospheric Hydroxyl. Science 331, Neumann, E Methanemissionen aus natürlichen Feuchtgebieten. Staatsexamensarbeit, Inst. F. Umweltphysik, Univ. Heidelberg. Peixoto, J.P. und A.H. Oort, 1993, Physics of Climate, American Institute of Physics, New York, 520 pp. Velders, G.J.M. et al The large contribution of projected HFC emissions to future climate forcing. PNAS 106,

58 Thank you!