Evaluating Northern Hemisphere growing season net carbon flux in climate models using aircraft observations

Understanding terrestrial ecosystems and their response to anthropogenic climate change requires quantification of land-atmosphere carbon exchange. However, top-down and bottom-up estimates of large-scale land-atmosphere fluxes, including the northern extratropical growing season net flux (GSNF), show significant discrepancies. We developed a data-driven metric for the GSNF using atmospheric carbon dioxide concentration observations collected during the High-Performance Instrumented Airborne Platform for Environmental Research Pole-to-Pole Observations and Atmospheric Tomography Mission flight campaigns. This aircraft-derived metric is bias-corrected using three independent atmospheric inversion systems. We estimate the northern extratropical GSNF to be 5.7 +/- 0.3 Pg C and use it to evaluate net biosphere productivity from the Coupled Model Intercomparison Project phase 5 and 6 (CMIP5 and CMIP6) models. While the model-to-model spread in the GSNF has decreased in the CMIP6 models relative to that of the CMIP5 models, there is still disagreement on the magnitude and timing of seasonal carbon uptake with most models underestimating the GSNF and overestimating the length of the growing season relative to the observations. We also use an emergent constraint approach to estimate annual northern extratropical gross primary productivity to be 56 +/- 17 Pg C, heterotrophic respiration to be 25 +/- 13 Pg C, and net primary productivity to be 28 +/- 12 Pg C. The flux inferred from these aircraft observations provides an additional constraint on large-scale gross fluxes in prognostic Earth system models that may ultimately improve our ability to accurately predict carbon-climate feedbacks.Plain Language Summary The exchange of carbon between the land and atmosphere is an important part of the Earth's climate, and this exchange might change due to human-caused climate change. However, estimates of land-atmosphere carbon fluxes made using different techniques do not agree with each other. We use atmospheric carbon dioxide observations collected during two flight campaigns to show that 5.7 Pg C is exchanged between the atmosphere and the land in the northern hemisphere during the summer growing season. This estimate is used to evaluate the performance of two generations of climate prediction models. The newer generation of models show less spread than the older generation, but there is still significant disagreement on the magnitude and timing of land-atmosphere carbon exchange among models. Most models underestimate the growing season net flux and overestimate the length of the growing season. We also use our observational estimate to reduce the spread on component fluxes of carbon exchange, namely uptake by photosynthesis and release by respiration.

To Access Resource:

Questions? Email Resource Support Contact:

  • opensky@ucar.edu
    UCAR/NCAR - Library

Resource Type publication
Temporal Range Begin N/A
Temporal Range End N/A
Temporal Resolution N/A
Bounding Box North Lat N/A
Bounding Box South Lat N/A
Bounding Box West Long N/A
Bounding Box East Long N/A
Spatial Representation N/A
Spatial Resolution N/A
Related Links

Related Dataset #1 : NOAA Global Monitoring Laboratory Carbon Cycle and Greenhouse Gases Group Continuous Insitu Measurements of CO2 at Global Background Sites, 1973-Present

Related Dataset #2 : NCAR CESM2-WACCM model output prepared for CMIP6 CMIP historical

Related Dataset #3 : NCC NorCPM1 model output prepared for CMIP6 CMIP historical

Related Dataset #4 : NCAR CESM2-FV2 model output prepared for CMIP6 CMIP historical

Related Dataset #5 : NCAR CESM2-WACCM-FV2 model output prepared for CMIP6 CMIP historical

Related Dataset #6 : CMCC CMCC-ESM2 model output prepared for CMIP6 CMIP historical

Related Dataset #7 : CCCma CanESM5 model output prepared for CMIP6 CMIP historical

Related Dataset #8 : CMCC CMCC-CM2-SR5 model output prepared for CMIP6 CMIP historical

Related Dataset #9 : CSIRO ACCESS-ESM1.5 model output prepared for CMIP6 CMIP historical

Related Dataset #10 : HAMMOZ-Consortium MPI-ESM1.2-HAM model output prepared for CMIP6 CMIP historical

Related Dataset #11 : IPSL IPSL-CM6A-LR model output prepared for CMIP6 CMIP historical

Related Dataset #12 : MPI-M MPI-ESM1.2-LR model output prepared for CMIP6 CMIP historical

Related Dataset #13 : NASA-GISS GISS-E2.1G model output prepared for CMIP6 CMIP historical

Related Dataset #14 : NASA-GISS GISS-E2.1H model output prepared for CMIP6 CMIP historical

Related Dataset #15 : NCAR CESM2 model output prepared for CMIP6 CMIP historical

Related Dataset #16 : NCC NorESM2-LM model output prepared for CMIP6 CMIP historical

Related Dataset #17 : NCC NorESM2-MM model output prepared for CMIP6 CMIP historical

Related Dataset #18 : AS-RCEC TaiESM1.0 model output prepared for CMIP6 CMIP historical

Related Dataset #19 : ATom: Merged Atmospheric Chemistry, Trace Gases, and Aerosols, Version 2

Related Dataset #20 : MIROC4-ACTM CO2 Inversion flux (2001-2020; case s050_ux4_gc3t)

Related Software #1 : CarbonTracker CT2019B

Additional Information N/A
Resource Format PDF
Standardized Resource Format PDF
Asset Size N/A
Legal Constraints

Copyright author(s). This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.


Access Constraints None
Software Implementation Language N/A

Resource Support Name N/A
Resource Support Email opensky@ucar.edu
Resource Support Organization UCAR/NCAR - Library
Distributor N/A
Metadata Contact Name N/A
Metadata Contact Email opensky@ucar.edu
Metadata Contact Organization UCAR/NCAR - Library

Author Loechli, M.
Stephens, Britton
Commane, R.
Chevallier, F.
McKain, K.
Keeling, R. F.
Morgan, E. J.
Patra, P. K.
Sargent, M. R.
Sweeney, C.
Keppel-Aleks, G.
Publisher UCAR/NCAR - Library
Publication Date 2023-02-01T00:00:00
Digital Object Identifier (DOI) Not Assigned
Alternate Identifier N/A
Resource Version N/A
Topic Category geoscientificInformation
Progress N/A
Metadata Date 2025-07-11T15:54:56.029721
Metadata Record Identifier edu.ucar.opensky::articles:26123
Metadata Language eng; USA
Suggested Citation Loechli, M., Stephens, Britton, Commane, R., Chevallier, F., McKain, K., Keeling, R. F., Morgan, E. J., Patra, P. K., Sargent, M. R., Sweeney, C., Keppel-Aleks, G.. (2023). Evaluating Northern Hemisphere growing season net carbon flux in climate models using aircraft observations. UCAR/NCAR - Library. https://n2t.org/ark:/85065/d7q2445r. Accessed 05 August 2025.

Harvest Source