why regional carbon budgets? scientific and policy background
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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 Canada Canadian Forest Service. Two Overarching Questions. - PowerPoint PPT PresentationTRANSCRIPT
MJ Apps, Canadian Forest Service Nov 2004
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
MJ Apps, Canadian Forest Service Nov 2004
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?
Two Overarching Questions
MJ Apps, Canadian Forest Service Nov 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 Provocative insight:
Kleidon Climatic Change 2004
MJ Apps, Canadian Forest Service Nov 2004
Variation in T and CO2 over last 4 glacial cycles
A stable mode of behaviour for at least the past ½ million years
Temperature
CO2
Future?Today
Falkowski et al., 2000
Petit et al., 1999
MJ Apps, Canadian Forest Service Nov 2004
Perturbed Active Carbon CyclePerturbed Active Carbon Cycle
Fossil deposits
And adds additional carbon to the active cycle
Human activity alters mechanisms of the 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
MJ Apps, Canadian Forest Service Nov 2004
2.4OceanUptak
e
Land Uptake
2.2Land-UseChange
6.3 F
Fuel, Cemen
t
Global Budget: Top Down Perspective
Atmosphere
Surface biosphere
Data for 1990sfrom Houghton 2003Re-analyses of Ocean (Plattner) and LUC data
Net: 0.7 1990s
Atmospheric accumulation rate3.2 GtC per year 1990s
2.9
6 GtC/yr - equivalent to burning all of Canada’s trees every two years.
MJ Apps, Canadian Forest Service Nov 2004
2.4OceanUptak
e
Land Uptake
2.2Land-UseChange
6.3 F
Fuel, Cemen
t
Global Budget: Main questions
Atmosphere
Surface biosphere
Atmospheric accumulation rate3.2 GtC per year 1990s
2.9
How good are estimates?Where are the release occurring?
How will they change over time?Can human behavior be modified?
MJ Apps, Canadian Forest Service Nov 2004
Similar set of questions
2.4OceanUptak
e
Land Uptake
2.2Land-UseChange
6.3 F
Fuel, Cemen
t
Global Budget: Main questions
Atmosphere
Surface biosphere
Atmospheric accumulation rate3.2 GtC per year 1990s
2.9
MJ Apps, Canadian Forest Service Nov 2004
2.4OceanUptak
e
Land Uptake
2.2Land-UseChange
6.3 F
Fuel, Cemen
t
Global Budget: Main questions
Atmosphere
Surface biosphere
Atmospheric accumulation rate3.2 GtC per year 1990s
2.9
What are the mechanism responsible?Where is the uptake occurring?
How will it change over time?Can management influence?
MJ Apps, Canadian Forest Service Nov 2004
REDUCE SOURCES INCREASE SINKS
Global Budget: Scoping mitigation opportunities
2.4OceanUptak
e
Land Uptake
2.2Land-UseChange
6.3 F
Fuel, Cemen
t
Atmosphere
Surface biosphere
Atmospheric accumulation rate3.2 GtC per year 1990s
2.9
Activities are undertaken within regions at local levelsComprehensive REGIONAL
budgets are needed for guidance
MJ Apps, Canadian Forest Service Nov 2004
Mitigation: carried out at local to regional scalesMitigation: 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
MJ Apps, Canadian Forest Service Nov 2004
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 timeR.A.Houghton, 2003.Global Change Biology 9: 500-509,
MJ Apps, Canadian Forest Service Nov 2004
Importance of mechanisms for land uptakeWhat we now know:• No single region is responsible• No single mechanism is responsibleRather • 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 timeGaining a quantitative understanding of the processes underlying the land uptake is INTRINSICALLY a REGIONAL AND LOCAL problem, with scaling up challenges REGIONAL CARBON BUDGETS
MJ Apps, Canadian Forest Service Nov 2004
Importance of mechanisms for land uptake
1) Different mechanisms different mitigation approaches
policy interest, scientific challenge
2) Different mechanisms different future trajectories (climate implications)
scientific challenge, policy need – though not always appreciated!
3) Ability to factor out direct human interventions from indirect responses and natural variability
policy request, strong scientific challenge
MJ Apps, Canadian Forest Service Nov 2004
Increased growth rate, decreased decomposition
Different factors important for different regions
Increased Site fertility(Carrying capacity)
Two broad mechanisms for land uptake
1. Changes in productivity (stimulated NPP, reduced respiration) in response to CO2, climate, nutrient, management …
Examples
•Disturbed soils•Forest Stand
Biomass+ detritus +soils
age
Site
Ci
Deceased site fertility, growth rate, …
MJ Apps, Canadian Forest Service Nov 2004
Two broad mechanisms for land uptake
2. Changes in demographics (age distribution) due to change in mortality (LUC or natural distrubances)
stand age
Ci
Site level• At landscape or regional scale, must take into account age distribution• Shift of average age to right increases C (i.e., landscape becomes a sink)• Shift to left decreases C (i.e. source)
MJ Apps, Canadian Forest Service Nov 2004
stand age
stan
d C
i
Biomass+ detritus +soils
Source Sink
Subtle scaling issue: Site to Landscape
Local Tower
But, significant time before C released during/after disturbance is recaptured
Net loss Net removal
Site scale accumulation
Must be very careful when scaling up site to
regional
Contribution to landscape
remains deficit for much longer than instantaneous measurement suggests
MJ Apps, Canadian Forest Service Nov 2004
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
Equivalent/complementary results (conservation of mass) IFF all significant fluxes, and all significant stock changes are accounted
Two basic approaches to carbon balance: 1) Flux estimates 2) Pool (stock) change
STAND LEVELCH4CO2
TOPS
STEMLITTER DEBRIS PRODUCTS
ROOTS
Soil
PEAT
STAND LEVELCH4CH4CO2CO2
TOPS
STEMLITTER DEBRISLITTER DEBRIS PRODUCTSPRODUCTS
ROOTS
Soil
ROOTSROOTSROOTSROOTS
Soil
PEATPEAT
Carbon balance at an ecosystem scalee.g., Barford et al (2001)(Harvard )
Carbon balance at a regional scale
e.g., Janssens et al (2004) (Europe)
Carbon balance at a global scale
e.g., Houghton (2003)
MJ Apps, Canadian Forest Service Nov 2004
2.9 ± 1.1 Land uptake
2.4 ± 0.7 Oceans
3.2 ± 0.1 GtC/yrAtmosphere increase
6.3 ± 0.4F Fuel,Cement
Atmosphere
Surface biosphere
2.2 ±0.8Land-UseChange
Forests
?Ocean
Circulation
?
•Sarmiento et al 1998•Peterson et al 2001
>8Gt/yr?
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
MJ Apps, Canadian Forest Service Nov 2004
• Carbon feedbacks from dieback in Amazon
Ignoring climate change
UptakeIncluding climate change
Release
Betts: Future changes (?) global & region scale
Regional changes with global significance
Betts et al 2004
MJ Apps, Canadian Forest Service Nov 2004 MJA IOS Mar 2004 23
Kurz and Apps, Ecol. Appl. 1999
With large C consequences
Note Change after 1970
Kurz and Apps: Contemporary, regional scale
Stand replacing disturbances in Canadian forests have changed over last 50 years
MJ Apps, Canadian Forest Service Nov 2004
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
Summary: Policy issues and challenges
MJ Apps, Canadian Forest Service Nov 2004
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
Summary: Science issues and challenges
MJ Apps, Canadian Forest Service Nov 2004
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
MJ Apps, Canadian Forest Service Nov 2004
Think globally, analyze locally