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Regional Carbon Budgets: Understanding the Science and Policy

This article discusses the scientific and policy background for comprehensive and dynamic carbon budgets, focusing on the impacts, adaptation measures, and mitigation strategies related to atmospheric carbon accumulation. It explores the mechanisms responsible for carbon uptake, the need for regional budgets, and the importance of understanding different mitigation approaches and future trajectories.

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Regional Carbon Budgets: Understanding the Science and Policy

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  1. Why regional carbon budgets?Scientific and Policy Background Scientific and policy requirements for comprehensive and dynamic carbon budgets Mike Apps GCP Scientific Steering Committee & Natural Resources CanadaCanadian Forest Service

  2. Two Overarching Questions How will rates of atmospheric C accumulation change? • Impacts • Adaptation measures Can the fluxes causing theatmospheric accumulation be controlled? • Mitigation: what can be done to reduce sources and or increase sinks • Can these be monitored effectively? • How long will they last?

  3. Provocativeinsight: Kleidon Climatic Change 2004 Active Carbon Cycle Exchange of 120 GtC/yr (land), and 90 GtC/yr (ocean) C is cycled, not permanently stored A natural cycle that has operated for at least 4 glacial cycles

  4. Today Future? A stable mode of behaviour for at least the past ½ million years Petit et al., 1999 Variation in T and CO2 over last 4 glacial cycles CO2 Temperature Falkowski et al., 2000

  5. Human activity alters mechanisms of the cycle And adds additional carbon to the active cycle Fossil deposits Perturbed Active Carbon Cycle Perturbed Active Carbon Cycle • How the Earth system handles these perturbations will determine the impacts • How human activities are modified will influence the magnitude and timing of the perturbation

  6. Net: 0.7 1990s Global Budget: Top Down Perspective Data for 1990s from Houghton 2003 Re-analyses of Ocean (Plattner) and LUC data Atmospheric accumulation rate 3.2 GtC per year 1990s Atmosphere Surface biosphere 6.3 F Fuel, Cement 2.2 Land-Use Change 2.9 Land Uptake 2.4 Ocean Uptake 6 GtC/yr - equivalent to burning all of Canada’s trees every two years.

  7. Global Budget: Main questions Atmospheric accumulation rate 3.2 GtC per year 1990s Atmosphere Surface biosphere 6.3 F Fuel, Cement 2.2 Land-Use Change 2.9 Land Uptake 2.4 Ocean Uptake How good are estimates? Where are the release occurring? How will they change over time? Can human behavior be modified?

  8. Similar set of questions Global Budget: Main questions Atmospheric accumulation rate 3.2 GtC per year 1990s Atmosphere Surface biosphere 6.3 F Fuel, Cement 2.2 Land-Use Change 2.9 Land Uptake 2.4 Ocean Uptake

  9. Global Budget: Main questions Atmospheric accumulation rate 3.2 GtC per year 1990s Atmosphere Surface biosphere 6.3 F Fuel, Cement 2.2 Land-Use Change 2.9 Land Uptake 2.4 Ocean Uptake What are the mechanism responsible? Where is the uptake occurring? How will it change over time? Can management influence?

  10. Activities are undertaken within regions at local levels Comprehensive REGIONAL budgets are needed for guidance REDUCE SOURCES INCREASE SINKS Global Budget: Scoping mitigation opportunities Atmospheric accumulation rate 3.2 GtC per year 1990s Atmosphere Surface biosphere 6.3 F Fuel, Cement 2.2 Land-Use Change 2.9 Land Uptake 2.4 Ocean Uptake

  11. Mitigation: carried out at local to regional scales Mitigation: Regional C Budget requirements: • Comprehensive/sectoral perspective • Implementation and accuracy • Spatially complete • Resolution appropriate for decision making or reporting • Appropriate time scales • Resolution years, horizon 10-100 yrs • Forecasting/scenario ability • Planning strategies • Tracking/monitoring ability with uncertainties • Evaluating, assessing, and adaptive management. Reporting • Transparency, credibility, explicit uncertainty • Accountability and comparability

  12. Global Perspective: reconciling top-down and bottom up Land uptake currently inferred as residual. • Bottom up estimates are incomplete – limited by sectors, regions, and data Houghton reviewed the recent top down and bottom up estimates and attempts to reconcile. Houghton concludes • global land net uptake : net tropical source and a net northern sink, • magnitudes depend on accuracy of estimates of tropical LUC and • Both net tropical source and net northern sink appear to change over time R.A.Houghton, 2003.Global Change Biology 9: 500-509,

  13. Importance of mechanisms for land uptake What we now know: • No single region is responsible • No single mechanism is responsible Rather • Spatial mosaic of sources and sinks – at many scales, across landscapes, across biomes, across regions • Biological sources and sinks are often autocorrelated (but with time delays) • The spatial mosaic changes with time Gaining a quantitative understanding of the processes underlying the land uptake is INTRINSICALLY a REGIONAL AND LOCAL problem, with scaling up challenges  REGIONAL CARBON BUDGETS

  14. Importance of mechanisms for land uptake • Different mechanisms  different mitigation approaches • policy interest, scientific challenge • Different mechanisms  different future trajectories (climate implications) • scientific challenge, policy need – though not always appreciated! • Ability to factor out directhuman interventions from indirect responses and natural variability • policy request, strong scientific challenge

  15. Site Ci • Examples • Disturbed soils • Forest Stand age Biomass+ detritus +soils Increased Site fertility(Carrying capacity) Increased growth rate, decreased decomposition Different factors important for different regions Deceased site fertility, growth rate, … Two broad mechanisms for land uptake • Changes in productivity (stimulated NPP, reduced respiration) in response to CO2, climate, nutrient, management …

  16. Two broad mechanisms for land uptake Site level Ci stand age • Shift of average age to right increases C (i.e., landscape becomes a sink) • Shift to left decreases C (i.e. source) • Changes in demographics (age distribution) due to change in mortality (LUC or natural distrubances) • At landscape or regional scale, must take into account age distribution

  17. But, significant time before C released during/after disturbance is recaptured Must be very careful when scaling up site to regional stand Ci stand age Source Sink Net loss Net removal Contribution to landscape remains deficit for much longer than instantaneous measurement suggests Subtle scaling issue: Site to Landscape Site scale accumulation Biomass+ detritus +soils Local Tower

  18. Carbon balance at a regional scale Carbon balance at a global scale Carbon balance at an ecosystem scale e.g., Janssens et al (2004) (Europe) e.g., Houghton (2003) Need for comprehensive system perspective At any scale, net flux to atmosphere is a complex balance of many individual time varying fluxes each having different controls • Two basic approaches to carbon balance: • Flux estimates • Pool (stock) change Equivalent/complementary results (conservation of mass) IFF all significant fluxes, and all significant stock changes are accounted e.g., Barford et al (2001)(Harvard )

  19. 3.2 ± 0.1 GtC/yr Atmosphere increase >8Gt/yr? Atmosphere Surface biosphere Ocean Circulation ? Forests ? 6.3 ± 0.4 F Fuel, Cement 2.2 ±0.8 Land-Use Change 2.9 ± 1.1 Land uptake 2.4 ± 0.7 Oceans Need for comprehensive system perspective Especially important in predicting future atmospheric carbon if some of the present feedbacks fail … Balance will be altered by global change • Cox et al 2000 • Kurz &Apps 1999 • Sarmiento et al 1998 • Peterson et al 2001

  20. Ignoring climate change Uptake Including climate change Release Regional changes with global significance Betts: Future changes (?) global & region scale • Carbon feedbacks from dieback in Amazon Betts et al 2004

  21. With large C consequences Note Change after 1970 Kurz and Apps, Ecol. Appl. 1999 Kurz and Apps: Contemporary, regional scale Stand replacing disturbances in Canadian forests have changed over last 50 years MJA IOS Mar 2004 23

  22. Summary: Policy issues and challenges Policy and decision makers focus on: • Likely impacts (party/country level and globally) • Of not doing anything (impacts and adaptation potential) • Of mitigation measures (cost/benefit) • Timing of these impacts • Feasible mitigation opportunities • Within country • Globally • Robust analysis of party (country) level budgets • Trade and negotiations • Planning and monitoring

  23. Summary: Science issues and challenges Quantitative understanding the spatial and temporal dynamics of the perturbed carbon cycle: • Reconciling top-down and bottom-up estimates of the global carbon budget • Understanding the mechanisms that control the major fluxes (anthropogenic and biospheric) making up the budget • Predicting how the budget will change over time • Observation and measurement challenges posed by the above needs

  24. The way forward? ‘Better’ regional carbon budgets • Data, comprehensive (processes, sectors, pools), spatial representation, dynamic that can be used • to constrain and augment global budgets • to inform decision makers at regional scales • to enable implementation of carbon management strategies • to monitor progress at relevant scales and facilitate adaptive management

  25. Think globally, analyze locally

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