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Global Change and the Carbon Cycle Michael Raupach 1,3,4, Pep Canadell 2 and Damian Barrett 2,1,4 1 CSIRO Earth Observation Centre, Canberra, Australia.

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Presentation on theme: "Global Change and the Carbon Cycle Michael Raupach 1,3,4, Pep Canadell 2 and Damian Barrett 2,1,4 1 CSIRO Earth Observation Centre, Canberra, Australia."— Presentation transcript:

1 Global Change and the Carbon Cycle Michael Raupach 1,3,4, Pep Canadell 2 and Damian Barrett 2,1,4 1 CSIRO Earth Observation Centre, Canberra, Australia 2 CSIRO Plant Industry, Canberra, Australia 3 Global Carbon Project (IGBP-IHDP-WCRP-Diversitas) 4 CRC for Greenhouse Accounting Thanks:Peter Briggs, Helen Cleugh, Mac Kirby, Rachel Law, Ray Leuning, Graeme Pearman, Peter Rayner, Steve Roxburgh, Will Steffen, Cathy Trudinger, YingPing Wang and to:AGO (Australia), NIES (Japan), and CRC for Greenhouse Accounting APN Symposium, Canberra, 23 March 2004

2 Outline u Carbon in the earth system u Global carbon budget u An Australian perspective u Inertia u Greenhouse mitigation u Vulnerability

3 Carbon in the earth system 1.Carbon is the building block of life u Forms large, reactive molecules which store and propagate information, enabling the evolutionary emergence of complex, self-organising systems u The carbon cycle is the crossroads for all major biogeochemical cycles 2.Carbon is a key to sustainable natural resource management 3.Managing the carbon cycle is key to greenhouse gas mitigation

4 Atmospheric CO 2 : past and future u Last 420,000 years: Vostok ice core record (blue) u Last 100 years: Contemporary record (red) u Next 100 years: IPCC BAU scenario (red)

5 Interactions between the carbon cycle and the climate system C cycle Aerosols IPCC Third Assessment (2001)

6 Global carbon budget u What goes in: Human contributions to enhanced atmospheric CO 2 u What stays or comes out: Fate of enhanced atmospheric CO 2 Data from IPCC Third Assessment (2001)

7 Global carbon budget Fluxes in GtC/year (summary from Sabine et al. 2004, SCOPE-GCP) 1980s 1990s Atmospheric C accumulation 3.3   0.2 IPCC 2001 = Emissions (fossil, cement) 5.4   0.6 IPCC Net ocean-air flux -1.9   0.5IPCC   0.7 le Quere et al Net land-air flux -0.2   0.7IPCC   0.8 le Quere et al 2003 Net land-air flux -0.3   0.8 = Land use change 2.0 (0.9 to 2.8) 2.2 (1.4 to 3.0)Houghton Residual terrestrial sink -2.3 (-4.0 to -0.3) -3.4 (-5.0 to -1.8) = Land use change 0.6 (0.3 to 0.8) 0.9 (0.5 to 1.4)de Fries et al Residual terrestrial sink -0.9 (-3.0 to 0) -2.1 (-3.4 to -0.9) u Global C budget from atmospheric signals (CO 2, 13 C, O 2 ) Ocean O 2 flux correction Remote sensing National data u Attribution of net land-air flux

8 SCOPE-GCP Rapid Assessment of the Carbon Cycle u Field CB, Raupach MR (eds.) (2004) The Global Carbon Cycle: Integrating Humans, Climate and the Natural World. Island Press, Washington D.C. 526 pp. u A joint initiative of Scientific Committee On Problems in the Environment (SCOPE) The Global Carbon Project (IGBP-IHDP-WCRP-Diversitas)

9 Interannual variability in the global C cycle Roger Francey, CSIRO Atmospheric Research

10 The current carbon cycle Sabine et al (2004, SCOPE-GCP)

11 Global carbon budget: conclusions u Main revision to IPCC Third Assessment (2001) is possible downward revision of C flux from land use change (from ~2 to ~1 PgC/y) from remote sensing evidence u This reduces magnitude of residual terrestrial sink (around −3 to −2 PgC/y) u Atmospheric accumulation has high interannual variability (more than ±2 PgC/y around a current mean of 3.2 PgC/y) u Most of this variability is attributable to the net land-air flux

12 u Australian NPP, NEP and NBP u Fire, Agriculture, Nitrogen u Definitions: Gross Primary Production: GPP = Photosynthetic assimilation Net Primary Production: NPP = GPP − Autotrophic Respiration Net Ecosystem Production: NEP = NPP − Heterotrophic Respiration Net Biome Production: NBP = NEP − Disturbance Emission (Fire) An Australian perspective GPP=1 R Auto R Het Dist NPP~0.5 NEP~0.1 Assim NBP~0

13 AVHRR-NDVI anomaly u Current version (Oct 2003) uses EOC "B-PAL" archive of AVHRR data u 5 km, 8-11 day composites u Still to incorporate: Atmos correction BRDF correction 1-km data u Peter Briggs, Edward King Jenny Lovell, Susan Campbell, Michael Raupach, Michael Scmidt Sonja Nikolova, Dean Graetz, Tim Mc Vicar

14 Mean annual NPP and NEP for Australia Xu and Barrett (2004) unpublished u Large interannual variability u Mean annual NPP = 740 TgC yr-1 (range 470 – 1032) u Mean annual NEP = 0.31 TgC yr-1 (range -81 to 118) u NEP calculated without fire, so actually an estimate of NBP

15 Comparing predicted Australian NEP and NBP with aircraft CO 2 measurements off the east coast u CO 2 and NEP are in antiphase u NBP has higher amplitude than NEP u Fire acts as an alternative oxidation pathway Aircraft [CO 2 ] over western Pacific and Australia (Matsueda et al 2002) NEP = GPP – R a – R h NBP = GPP – R a –R h – Fire emissions Xu and Barrett (2004) submitted Global Change Biology

16 Global NEP gC/m2/y Model-data synthesis Models: u terrestrial biosphere (BETHY) u atmospheric transport model Data: u remote sensing u atmospheric CO 2 NEE uncertainty Peter Rayner, CSIRO Atmospheric Research

17 CenW Miami Berry Miami Oz Vast Grasp dLdP Olson RFBN Century BiosEquil SDGVM Hybrid Triffid VECODE LPJ IBIS Roxburgh et al 2004 Estimates of Australian NPP Global average NPP Evidence from: * C inventories * CO 2 (Cape Grim)

18 Effect of agriculture on Australian Net Primary Production u Australian NPP without agricultural inputs of nutrients and water u Ratio: (NPP with agric) / (NPP without agric) u Largest local NPP changes: around x 2 u Continental change in C cycle: 1.07 u Continental change in N cycle: around 2 Raupach, M.R., Kirby, J.M., Barrett, D.J., Briggs, P.R., Lu, H. and Zhang, L. (2002). Balances of water, carbon, nitrogen and phosphorus in Australian landscapes: Bios Release CD- ROM (19 April 2002). CSIRO Land and Water.

19 Without agriculture N flux (kgN/m2/yr) With agriculture Fert Dep Fix Gas Leach Disturb Australian nitrogen balance and the effect of agriculture Raupach, M.R., Kirby, J.M., Barrett, D.J., Briggs, P.R., Lu, H. and Zhang, L. (2002). Balances of water, carbon, nitrogen and phosphorus in Australian landscapes: Bios Release CD- ROM (19 April 2002). CSIRO Land and Water.

20 Comparing fluxes in the Australian and global C cycles u Averagia: a land mass of the same area as Australia, but with the same biogeochemical fluxes as the global terrestrial average Flux AustraliaAveragia MeanRangeMean NPP(MtC/y)−780 (−1032 to −470) −2850(by area) NBP(MtC/y) −0.31 (−118 to +81) −60(by area) NEP(MtC/y) ? (?) −105(by area) Fire emission(MtC/y) (+77 to +142) + 45(by area) Fossil-fuel C emission+ 103 (small) + 21(by population) Rainfall (mm) Australian C fluxes from Xu and Barrett (2004, unpublished); global values from de SCOPE-GCP 2004 (de Fries LUC) Relative to Averagia, Australia has: about 1/3 the NPP, but 2/3 the rainfall negligible NBP twice the fire emissions over 4 times the per capita fossil fuel emission

21 Inertia in the coupled carbon-climate-human system Field, Raupach and Victoria (2004, SCOPE-GCP)

22 Global temperature change CO 2 Emissions (PgCyr -1 ) CO 2 Concentration (ppm) Inertia in the coupled carbon-climate-human system 650 IPCC Third Assessment (2001)

23 Inertia: conclusions u Time scales (years) for system components: Land-air C exchange10 to 100 Ocean-air C exchange100 to 1000 Economic development20 to 200 Technology to decarbonise energy10 to 100 Development of political will to act globally? Development of institutions? u Stabilisation (of CO 2 level or temperature) requires anthropogenic C emissions to fall eventually to near zero: this will take over a century u Temperature will continue to rise slowly (few tenths of degree per century) long after CO 2 stabilisation, because of long-time-scale ocean inertia

24 Greenhouse mitigation u Carbon gap u Potential and actual mitigation u Ancillary effects

25 The carbon gap Edmonds et al. (2004, SCOPE-GCP) u The carbon gap is the difference between presently projected C emissions and the emission trajectory required for stabilisation CO 2 Emissions (PgCyr -1 ) Effect of technological development Carbon gap

26 Matching C emissions to CO 2 stabilisation pathways Case 1 = "Business as usual" (IS92A) Case 2 = Case 1 with major CO2 sequestration and disposal Case 3 = Case 2 with major energy conservation and use of non-fossil-fuel energy SCOPE-GCP (2004)

27 Mitigation Potential = Carbon Sequestered or GHG emissions avoided, as a fraction of technical potential mitigation Cost of carbon ($/tCeq) Technical Potential Baseline Potential Environmental factors Social and institutional factors Economic factors Sustainably Achievable Potential 01 Uptake proportion at given cost Mitigation Potential u Effects of economic, environmental and social-institutional factors on the mitigation potential of a carbon management strategy SCOPE-GCP (2004)

28 Ancillary effects: economic, environmental and socio-cultural impacts of mitigation strategies SCOPE-GCP (2004)

29 Greenhouse mitigation: conclusions u Even business-as-usual projections for fossil fuel emissions include very substantial technical innovation (efficiency, reductions in fossil fuel share of energy, …) u A mix of all effective strategies is required: Conservation Non-fossil-fuel energy sources Land-based options (reduction in land use change, biofuels) Geological disposal u Achievable mitigation potential is often much less (10 to 20-% of) technical potential u Uptake of a given strategy is (presently) largely determined by ancillary benefits and costs, not greenhouse mitigation outcome

30 Atmospheric CO 2 Warming Fossil Fuel burning (+) CO 2 emissions (+) Vulnerability of biospheric C pools (+) Vulnerability in the carbon cycle u Vulnerability of a C pool is the risk of accelerated carbon release from that pool as climate change occurs because of a positive feedback [d(flux)/d(climate) > 0]

31 Vulnerable carbon pools in the 21st century Gruber et al. (2004, SCOPE-GCP) Carbon in terrestrial vegetation: 650 Pg

32 Vulnerability of terrestrial C sink: saturation level of terrestrial C sink depends on mechanism u The global terrestrial biospheric carbon sink … Sink strength will increase and saturate in the future if the dominant mechanism is CO 2 and N fertilisation (CO 2 saturation around 600 ppm) will decrease in the near future if the dominant mechanism is regrowth and fire suppression Sink strength Climate warms as predicted (eg Cox et al 2000) Climate warms more rapidly than predicted 2%98% Sink attribution in Eastern US for 1980 to1999 (Caspersen et al. 2000)

33 Vulnerability of terrestrial C sink: the fire bomb u Terrestrial C sinks: for how long and at what ultimate cost? Swetnam et al.

34 Canberra, 18 January 2003

35

36 Vulnerability in the C cycle: conclusions u Stores of ~400 PgC are at moderate risk over the next century. Release of these stores would add ~200 ppm to atmospheric CO 2 concentrations. u Vulnerability increases as climate change occurs. u If CO 2 fertilisation is the main mechanism for the global terrestrial sink, the sink will last for 50 to 100 years BUT If the global terrestrial sink is largely due to forest regrowth and fire suppression then terrestrial sinks will disappear within a few decades.

37 Summary u Carbon in the earth system: The building block of life A key to sustainable natural resource management Key to greenhouse gas mitigation u Carbon cycle science is rapidly improving our knowledge of The spatial and temporal patterns (dynamics) in the C cycle Processes, feedbacks and interactions The connections between biophysical C cycle and human activities.

38 Hilary Talbot


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