1. Atmospheric CO2 and O2 Observations and the Global Carbon Cycle
Current budget uncertainties
HIPPO (HIAPER Pole-to-Pole Observations of Atmospheric Tracers)
RACCOON (Regional Atmospheric Continuous CO2 Network)
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Britt Stephens, NIWA Wellington 1

2. Climate projections are sensitive to human decisions and carbon cycle feedbacks. . .
[IPCC, 2007]

3. Annual fluxes are small relative to balanced seasonal exchanges and to standing pools
Annual residuals
Pools and flows
(PgCyr-1)
Net Oceanic Sink
Land-Based Sink
Uncertainties on natural annual-mean ocean and land fluxes are +/- 25 to 75 %
The global carbon cycle for the 1990s, showing the main annual fluxes in PgC yr –1. [IPCC, 2007]

4. Global atmospheric inverse models and surface data can be used to make regional flux estimates
Forward: Flux + Transport = [CO2]
Inverse: [CO2] – Transport = Flux

5. 12 model results from the TransCom3 Level 2 study
Systematic trade off between northern and tropical land fluxes
Model
Model Name 1
CSU 2
GCTM 3
UCB 4
UCI 5
JMA 6
MATCH.CCM3 7
MATCH.NCEP 8
MATCH.MACCM2 9
NIES A
NIRE B
TM2 C
TM3

6. Regional land flux uncertainties are very large
All model average and standard deviations:
Northern Land = -2.4 ± 1.1 PgCyr-1
Tropical Land = +1.8 ± 1.7 PgCyr-1

7. Comparing observed and modeled vertical CO2 gradients
3 models that most closely reproduce the observed annual-mean vertical CO2 gradients (4, 5, and C):
Northern Land =
-1.5 ± 0.6 PgCyr-1
Tropical Land =
+0.1 ± 0.8 PgCyr-1
All model average:
-2.4 ± 1.1 PgCyr-1
+1.8 ± 1.7 PgCyr-1
Northern Land
Tropical Land
Most of the models overestimate the annual-mean vertical CO2 gradient
observed value
[Stephens et al., Science, 2007]

8. HIAPER Pole-to-Pole Observations of Atmospheric Tracers
HIPPO (PIs: Harvard, NCAR, Scripps, and NOAA): A global and seasonal survey of CO2, O2, CH4, CO, N2O, H2, SF6, COS, CFCs, HCFCs, O3, H2O, black carbon, and hydrocarbons
5 loops over 3 years, first was in January 2009

9. NCAR Airborne Oxygen Instrument (AO2)
measures O2 concentration using a vacuum-ultraviolet absorption technique
designed specifically for airborne use to minimize motion and thermal sensitivity and with a pressure and flow controlled inlet system
switches between sample and reference gases every 2 seconds and has a precision of +/- 2 per meg on a 4-second measurement
consists of pump, cylinder, and instrument modules, and a dewar

10. START-08/pre-HIPPO Campaign, April - June 2008, descent into Grand Forks, North Dakota

11. Descent into Christchurch, 18 January, 2009

12. Profile over Lauder, 20 January, 2009

15. HIPPO CO2 Cross Section, January, 2009
AO2 Instrument

16. HIPPO O2 Cross Section, January, 2009

17. HIPPO APO Cross Section, January, 2009
Atmospheric Potential Oxygen:
APO = O *CO2

18. Harvard and NOAA Data

19. Planned CO2 comparisons
AO2 Instrument
[data courtesy A. Jacobson and the CT Team, as compiled by S. Mikaloff-Fletcher]

20. Planned APO comparisons
[TransCom model runs from T. Blaine dissertation. Fossil fluxes not included]

21. Regional Atmospheric Continuous CO2 Network in the Rocky Mountains (Rocky RACCOON,
North American Continuous CO2 Sites
SPL FEF
[courtesy N. Miles]
NWR HDP EFS

22. Regional Atmospheric Continuous CO2 Network in the Rocky Mountains (Rocky RACCOON,

23. Autonomous Inexpensive Robust CO2 Analyzer (AIRCOA)
NCAR - NOAA: ± 0.21 ppm n = 347

24.
ccgg/carbontracker/index.html

25. Fraser Experimental Forest Noctural Respiration Signals
Ecosystem respiration decreases, because reduction in autotrophic respiration is greater than increase in heterotrophic respiration

26. Conclusions:
Advancing our understanding of the carbon cycle requires many more good observations and much better models
Ongoing and planned collaborations at NIWA, and with other organizations, are addressing both of these fronts
Including:
Lauder column and in situ observations
Baring Head observations
CarbonTracker model
Southern Ocean CO2 and O2 studies
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28. Regional Atmospheric Continuous CO2 Network in the Rocky Mountains (Rocky RACCOON,
North American Continuous CO2 Sites
[courtesy N. Miles]