aircraft co 2 observations and global carbon budgeting
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Aircraft CO2 Observations and Global Carbon Budgeting
Britton Stephens, NCAR EOL and TIIMES
Collaborating Institutions:
USA: NOAA GMD, CSU, France: LSCE, Japan: Tohoku Univ., NIES, Nagoya Univ., Russia: CAO, SIF, England: Univ. of Leeds, Germany: MPIB, Australia: CSIRO MAR
Carbon cycle science as a field began with the careful observational work of Dave Keeling
Keeling, C.D., Rewards and penalties of monitoring the earth, Annu. Rev. Energy Environ., 23, 25-82, 1998.
IGY started 50 years ago this month
Annual-mean CO2 exchange (PgCyr-1) from atmospheric O2
Surface Observations
TransCom1 fossil-fuel gradients
Global and hemispheric constraints on the carbon cycle
1.8 ± 0.8
0.3 ± 0.9 5.4 ± 0.3
2.2 ± 0.4
6.4 ± 0.41.0 ± 0.6
IPCC, 2007
[courtesy of Scott Denning]
[figure courtesy of Scott Denning]
Seasonal vertical mixing
Transcom3 neutral biosphere flux response
349.5
350.0
350.5
351.0
351.5
352.0
352.5
353.0
353.5
354.0
-90 -70 -50 -30 -10 10 30 50 70 90
CSU.gurney
GISS.fung
GISS.prather
GISS.prather2
GISS.prather3
J MA-CDTM.maki
MATCH.bruhwiler
MATCH.chen
MATCH.law
NIES.maksyutov
NIRE.taguchi
RPN.yuen
SKYHI.fan
TM2.lsce
TM3.heimann
GCTM.baker
Latitude
ppm
“Rectifier Effect”
Gurney et al, Nature, 2002
TransCom3 model results based on surface data imply a large transfer of carbon from tropical to northern land regions.
Level 1 (annual mean)Level 2 (seasonal)
Gurney et al, GBC, 2004
Bottom-up estimates have generally failed to find large uptake in northern ecosystems and large net sources in the tropics
Model Model NameNorthern
Total Flux (1)Tropical
Total Flux (1)Northern
Land Flux (1)Tropical
Land Flux (1)
1 CSU -4.4 (0.2) 3.7 (0.6) -3.6 (0.3) 3.3 (0.7)
2 GCTM -3.4 (0.2) 2.3 (0.7) -2.0 (0.3) 2.7 (0.8)
3 UCB -4.4 (0.3) 3.7 (0.6) -3.1 (0.3) 4.0 (0.7)
4 UCI -2.6 (0.3) 0.5 (0.7) -1.5 (0.3) -0.1 (0.8)
5 JMA -1.4 (0.3) -0.5 (0.8) -0.9 (0.4) -0.5 (0.9)
6 MATCH.CCM3 -3.0 (0.2) 2.2 (0.6) -2.1 (0.3) 2.3 (0.7)
7 MATCH.NCEP -4.0 (0.2) 3.2 (0.5) -4.0 (0.3) 3.4 (0.7)
8 MATCH.MACCM2 -3.7 (0.3) 3.1 (0.8) -3.0 (0.3) 2.5 (0.9)
9 NIES -4.0 (0.3) 2.2 (0.6) -3.5 (0.3) 2.7 (0.8)
A NIRE -4.5 (0.3) 1.6 (0.7) -2.8 (0.3) 1.2 (0.8)
B TM2 -1.6 (0.3) -1.4 (0.7) -0.5 (0.3) -1.0 (0.8)
C TM3 -2.4 (0.2) 1.4 (0.6) -2.2 (0.3) 1.0 (0.8)
TransCom 3 Level 2 annual-mean model fluxes (PgCyr-1)
Study N. Total T. Total N. Land T. Land
Jacobson et al., 2006 ('92-'96) -3.9 5.0 -2.9 4.2
Baker et al., 2006 ('91-'00) -3.7 2.7 -2.6 1.9
Gurney et al., 2004 ('92-'96) -3.3 1.8 -2.4 1.8
CarbonTracker, 2007 ('01-'05) -2.8 1.1 -1.8 0.1
Rödenbeck et al., 2003 ('92-'96) -2.3 -0.1 -0.7 -1.0
Rödenbeck et al., 2003 ('96-'99) -2.1 0.3 -0.4 -0.8
Comparison to other studies
fluxes in PgCyr-1 = GtCyr-1 = “billions of tons of C per year”
@ $3 - $30 / ton, 3 PgCyr-1
~ $10 - $100 billion / year
TransCom3 predicted rectifier explains most of the variability in estimated fluxes
Impact on predicted fluxes
349.5
350.0
350.5
351.0
351.5
352.0
352.5
353.0
353.5
354.0
-90 -70 -50 -30 -10 10 30 50 70 90
CSU.gurney
GISS.fung
GISS.prather
GISS.prather2
GISS.prather3
J MA-CDTM.maki
MATCH.bruhwiler
MATCH.chen
MATCH.law
NIES.maksyutov
NIRE.taguchi
RPN.yuen
SKYHI.fan
TM2.lsce
TM3.heimann
GCTM.baker
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
ppm
pres
sure
N S N S N S N S
Transcom3 neutral biosphere flux response
Northern Hemisphere sites include Briggsdale, Colorado, USA (CAR); Estevan Point, British Columbia, Canada (ESP); Molokai Island, Hawaii, USA (HAA); Harvard Forest, Massachusetts, USA (HFM); Park Falls, Wisconsin, USA (LEF); Poker Flat, Alaska, USA (PFA); Orleans, France (ORL); Sendai/Fukuoka, Japan (SEN); Surgut, Russia (SUR); and Zotino, Russia (ZOT). Southern Hemisphere sites include Rarotonga, Cook Islands (RTA) and Bass Strait/Cape Grim, Australia (AIA).
Map of airborne flask sampling locations
Airborne flask sampling data
Altitude-time CO2 contour plots for all sampling locations
20
-15
10
-10
10
-10
0
-5
Model-predicted NH Average CO2 Contour Plots
Observed NH Average CO2 Contour Plot
Vertical CO2 profiles for different seasonal intervals
Observed and predicted NH average profiles
• 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:
Northern Land = -2.4 ± 1.1 PgCyr-1
Tropical Land = +1.8 ± 1.7 PgCyr-1
Estimated fluxes versus predicted 1 km – 4 km gradients
Observed value
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
• Interlaboratory calibration offsets and measurement errors
• Diurnal biases
• Interannual variations and long-term trends
• Flight-day weather bias
• Spatial and Temporal Representativeness
Observational and modeling biases evaluated:
All were found to be small or in the wrong direction to explain the observed annual-mean discrepancies
[Schulz et al., Environ. Sci. Technol. 2004, 38, 3683-3688]
WLEF Diurnal Cycle Observations
Estimated fluxes versus predicted 1 km – 4 km gradients for different seasonal intervals
Observed values
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
• Models with large tropical sources and large northern uptake are inconsistent with observed annual-mean vertical gradients.
• A global budget with less tropical-to-north carbon transfer is more consistent with bottom-up estimates and does not conflict with independent global 13C and O2 constraints.
• The mean of systematically varying model results is meaningless.
• Simply adding airborne data into the inversions will not necessarily lead to more accurate flux estimates
• Models’ seasonal vertical mixing must be improved to produce flux estimates with high confidence
• There is value in leaving some data out of the inversions to look for systematic biases
Conclusions:
• Improved carbon flux estimates will come from models with improved transport, assimilation of discrete samples, and more comprehensive atmospheric observations.
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, and hydrocarbons
HIAPER Pole-to-Pole Observations of Atmospheric Tracers
Fossil fuel CO2 gradients over the PacificUCI UCIs
JMA MATCH.CCM3
ppm
pres
sure
pres
sure
S N S N S N
N S
N S
N S
N S
Science, June 22, 2007
graphic from NCAR communications (Steve Deyo)
Airborne CO2 measurements indicate:
• Northern forests, including U.S. and Europe, are taking up much less CO2 than previously thought
• Intact tropical forests are strong carbon sinks and are playing a major role in offsetting carbon emissions
Implications of this work:
• Helps to resolve a major environmental mystery of the past two decades
Northern “missing carbon sink” has not been found because it is not there
• Improved understanding of processes responsible for carbon uptake will improve predictions of climate change and assessment of mitigation strategies
1
1Faraday, 1855
TransCom3 Modelers:Kevin R. Gurney, Rachel M. Law, Scott Denning, Peter J. Rayner, David Baker, Philippe Bousquet, Lori Bruhwiler, Yu-Han Chen, Philippe Ciais, Inez Y. Fung, Martin Heimann, Jasmin John, Takashi Maki, Shamil Maksyutov, Philippe Peylin, Michael Prather, Bernard C. Pak, Shoichi Taguchi
Aircraft Data Providers:Pieter P. Tans, Colm Sweeney, Philippe Ciais, Michel Ramonet, Takakiyo Nakazawa, Shuji Aoki, Toshinobu Machida, Gen Inoue, Nikolay Vinnichenko, Jon Lloyd, Armin Jordan, Martin Heimann, Olga Shibistova, Ray L. Langenfelds, L. Paul Steele, Roger J. Francey
Additional Modeling:Wouter Peters, Philippe Ciais, Philippe Bousquet, Lori Bruhwiler
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