1. A comparison of recent model- and inventory- based estimates of the continental-scale carbon balance of North America A. David McGuire USGS / University of Alaska Fairbanks North American Carbon Program 3 rd All-Investigators Meeting New Orleans – 3 February 2011 A. David McGuire USGS / University of Alaska Fairbanks North American Carbon Program 3 rd All-Investigators Meeting New Orleans – 3 February 2011

2. “Fast-Track” Analysis: Model– vs. Inventory– based Data Comparisons A component of the North American Carbon Program’s Regional / Continental Interim Synthesis Activities Organizing – Dave McGuire – Mac Post – Dan Hayes Inventory-based data – Graham Stinson, Werner Kurz (Canada Forest Inventory) – Brian McConkey (Canada Cropland Inventory) – Linda Heath (U.S. Forest Inventory) – Tris West (U.S. Cropland Inventory) – Ben deJong (Mexico) Model-data processing – Yaxing Wei – NACP Regional/Continental Interim Synthesis Participants Data analysis – Dan Hayes – Dave Turner Organizing – Dave McGuire – Mac Post – Dan Hayes Inventory-based data – Graham Stinson, Werner Kurz (Canada Forest Inventory) – Brian McConkey (Canada Cropland Inventory) – Linda Heath (U.S. Forest Inventory) – Tris West (U.S. Cropland Inventory) – Ben deJong (Mexico) Model-data processing – Yaxing Wei – NACP Regional/Continental Interim Synthesis Participants Data analysis – Dan Hayes – Dave Turner

3. Introduction Current understanding of state of the North American Carbon Cycle (e.g., SOCCR; King et al., 2007): – Magnitude of sink, trends, driving forces, uncertainty

4. Introduction Methodologies for assessing continental-scale carbon balance: – Inventory-based methods (forest stock changes, crop productivity, harvest and soil stocks, land use change) – Forward modeling: terrestrial biosphere process-based models – “top-down” observations with an Inverse approach via atmospheric transport modeling * Data and model results contributed to the NACP Regional / Continental Interim Synthesis activity

5. Inventory Reporting Zones Canada (n=15) U.S. (n=49) Mexico (n=32) no data

6. Inventory-data Analysis Conceptual diagram of the continental-scale carbon budget (including NEE) from the inventory-based approaches.

7. Inventory-based NEE estimates FOREST LANDSCROPLAND“OTHER” LANDSTOTAL

8. Inventory-based estimates Fate of Harvested (Forest & Crop) Carbon FOREST HARVESTCROP HARVESTTOTAL HARVEST

9. n = 17 n = 7 Model (Forward and Inverse) Data & Methods

10. * Distributing model output data variables across sector (Forestland, Cropland, and “Other”) within each reporting zone Model-data Processing

12. Compare NEE by country / sector

13. Mean average annual NEE (gC m -2 yr -1 ) for each reporting zone. Compare NEE spatial patterns

14. Compare Component Flux Estimates

16. Discussion What does it all mean? – Lack of convergence between approaches Different Approaches: – Strengths and weaknesses of each – Is our inventory approach (e.g. harvested product transfers and emissions) realistic? How can we reconcile with modeling approaches? – Inventory data gaps and uncertainties? – Uncertainties in the inverse approach: observation network, flux priors, transport models – Variability in the forward modeling approach: driver data, model formulations, processes / mechanisms simulated Formal model inter-comparisons?