anthropogenic carbon in a varying ocean
DESCRIPTION
Fortunat Joos, Thomas Fr öhlicher Climate and Environmental Physics, Physics Institute, University of Bern www.climate.unibe.ch /~joos CARBOOCEAN Meeting Bremen, December, 2006 Thanks to C. Lo Monaco, A. Velo and co-workers to the MPI and IPSL modelling groups. Anthropogenic carbon in - PowerPoint PPT PresentationTRANSCRIPT
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Anthropogenic carbon in
a varying ocean
Fortunat Joos, Thomas Fröhlicher
Climate and Environmental Physics,
Physics Institute, University of Bern
www.climate.unibe.ch/~joos
CARBOOCEAN Meeting
Bremen, December, 2006
Thanks to C. Lo Monaco, A. Velo and co-workers
to the MPI and IPSL modelling groups
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Data from the past show that anthropogenic climate change is proceeding at high speed
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(IPCC, 2007, Fig. TS-2a)Time (years before present)Time (years before present)
COCO22 versus Antarctic Temperature versus Antarctic Temperature
002000020000 1000010000
The atmospheric concentration of carbon dioxide in 2005 exceeds by far the natural range over the last 650,000 years (180 to 300 ppm) as determined from ice cores (IPCC, SPM, 2007).
Nat
ura
l Ran
geN
atu
ral R
ange
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What about rates of change?
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(Joos and Spahni, PNAS, submitted)
The age distribution of air enclosed in ice
Greenland CH4
Antarctic (Dome C), today
Antarctic (Dome C), Last Glacial Maximum
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(Joos and Spahni, PNAS, submitted)
The rate of increase
in the combined
radiative forcing
from CO2, CH4 and
N2O during the
industrial era is very
likely to have been
unprecedented in
more than 10,000
years (IPCC, SPM,
2007)
Rates of Change over the past 22,000 years
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Models and system understanding: current carbon emissions will affect the climate for many millennia
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Long-term CO2 and sea level
committmentin EMICs1820 -2100
2000 2500 3000
2000 2500 3000
Year
60%
60%
0
60%Atmosphere
Ocean
Land
2000 GtC
Thermal Expansion (m)
1
IPCC AR4 EMIC Intercomparison
Plattner et al., J.Clim., 2007;
Cumulative Emissions
0%
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IPCC Scenario Meeting, Sep 2007
•A new set of emission mitigation andbaseline scenarios
• Four scenarios to be selected for AOGCM runs
→ use in CARBOOCEAN
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Projected CO2 in 2100
Baseline Mitigation650 to 950 ppm 380 to 620 ppm
(Van Vuren et al., submitted)
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-1
0
1
2
3
4
5
6
7
8 b)
Tem
pera
ture
incr
ea
se (
o C)
MESSAGEMITMiniCamIMAGEIPACAIM
0
4
8
12
16 a)
Ra
dia
tive
forc
ing
(W
/m2
)
Baseline scenarios CS + CC Bern CS + CC MAGICC CS MAGICC
Mitigation scenario CS + CC Bern CS + CC MAGICC CS MAGICC
Bern mean MAGICC mean
MESSAGEMITMiniCamIMAGEIPACAIM
1900 1950 2000 2050 2100-1
0
1
2
3
4
5
6
7
8 c)
Te
mp
era
ture
incr
ea
se (
o C)
time0 500 1000 1500 2000
-1
0
1
2
3
4
5
6
7
8 d)
Uncertainty range BernUncertainty range MAGICC
Tem
pera
ture
incr
ea
se (
o C)
Cumulative CO2 emissions 2000-2100 (GtC)
Bern MAGICC
(Van Vuren et al., submitted)
Baseline MitigationRadiative Forcing (W m-2): 6 to 10 2.4 to 5.1CO2 (ppm): 650 to 950 380 to 620
Projected Radiative Forcing in 2100
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-1
0
1
2
3
4
5
6
7
8 b)
Tem
pera
ture
incr
ease
(o C
)
MESSAGEMITMiniCamIMAGEIPACAIM
0
4
8
12
16 a)
Rad
iativ
e fo
rcin
g (W
/m2)
Baseline scenarios CS + CC Bern CS + CC MAGICC CS MAGICC
Mitigation scenario CS + CC Bern CS + CC MAGICC CS MAGICC
Bern mean MAGICC mean
MESSAGEMITMiniCamIMAGEIPACAIM
1900 1950 2000 2050 2100-1
0
1
2
3
4
5
6
7
8 c)
Te
mpe
ratu
re in
crea
se (
o C)
time0 500 1000 1500 2000
-1
0
1
2
3
4
5
6
7
8 d)
Uncertainty range BernUncertainty range MAGICC
Tem
pera
ture
incr
ease
(o C
)
Cumulative CO2 emissions 2000-2100 (GtC)
Bern MAGICC
(Van Vuren et al., submitted)
Baseline Mitigation2.6 to 4.6°C 1.1 to 2.4°C
Projected Temperature Change (1990 to 2100)
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Are there critical thresholds ...?
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.
Ocean Acidification and Aragonite Saturation
Observation-based
NCAR CSM1.4
su
pe
rsa
turatio
n
A
2
1
4
3
0
A2
1
4
3
0(Steinacher, 2007)
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Evolution of Aragonite Saturation in the Surface
Surface pCO2 (ppm)
Lat
itu
de
90oS
90oN
300 500 700
su
pe
rsa
turatio
n
A
2
1
4
3
0
(Steinacher, 2007)
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Fluxes of calcite and aragonite to depth
CaCO3 flux in PISCES (PgC/m2/y)
Aragonite
Calcite
Total CaCO3
Gangsto, in prep. CaCO3 Flux (PgC/yr)
Dep
th (
m)
0
5000
Total CaCO3
Calcite
Aragonite
Will dissolution of shallow aragonitesediments mitigate some of the ocean acidification signal? Magnitude? Time scales?
0 0.80.4
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460 ppm: Arctic Ocean becomes undersaturated with respect to Aragonite
560 ppm: Antarctic surface waters become undersaturated
560 ppm: surface water that is more than 3 times oversaturated dissappears
Conclusions: Ocean Acidification
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How well do different
reconstruction methods of Canth
work in the AOGCM model world?
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a) Canth simulated by model
b) Canth reconstructed from simulated tracers (C, Alk, O2, ...)
Simulated and reconstructed Canth should beidentical
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a) Canth simulated by model
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.
NCAR CSM1.4
Surface Temperature and CO2 for SRES A2 and B1
1900 2000 2100Year
300
500
700C
O2 (
pp
m)
0
1
2
T (
oC
)
A2
B1
A2
B1
Anthropogenic forcing- Fossil and land use CO2 emissions- CH4, N2O, CFCs- direct sulphate aerosols
Natural forcing- solar irradiance- stratospheric volcanic aerosols
1900 2000 2100Year
Instrumental
Data
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.
Observation-based (GLODAP)
Anthropogenic CO2
NCAR CSM1.4
Can
th (m
ol m
-2)
0
50
100
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Change in decadal-mean PO4 from 1820 to 2000 AD, Atlantic, 20 W
Dep
th (
m)
80oS 60oN
0
40
P
O4 *117 (
mo
l-C/kg
)
-40
0
4500
• No century-scale trends• decadal variability in high latitudes of NA
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Modelled evolution of DIC and Canth for an individual grid cell (60 N, 20 W)
Remove natural variability in DIC by splining to get Canth
DIC
(m
mo
l/m
3)
Time
Canth
DIC
2180
21001850 20001900 1950
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Canth in the Atlantic along 20 WNCAR CSM1.4, 1994
Dep
th (
m)
80oS 60oN
30
70
0
Can
th (
mo
l-C/kg
)
-10
0
5000
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b) Canth reconstructed from simulated tracers (Carbon, Alk, O2, ...)
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The TrOCA method as an example
The usual assumptions
- Fixed Redfield ratios to correct for remineralisation- No century-scale trends- time-invariant air-sea disequilibrium
22
1 10.5 exp( )T T TCanth C O A b c dA
a a
„Organic MatterRemineralization“
„CaCO3dissolution“
Total Carbon
„preindustrialTotal Carbon“
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Canth in the Atlantic along 20 WTrOCA with NCAR output, 1994
Dep
th (
m)
0
Can
th (
mo
l-C/kg
)
80oS 60oN
0
5000
70
30
-10
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a) Canth simulated by model
b) Canth reconstructed from simulated tracers (T, S, O2, ...)
Are simulated and reconstructed Canth identical?
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TrOCA-NCAR
„truth“, NCAR-Model
0
70
-10
(m
ol-C/kg)
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Potential Problems
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Oxygen in NCAR
TrOCA
Remineralisation of organic matter does not consumeO2 in oxygen minimum zones (OCMIP Protocoll)
Remineralisation and Canth is overestimatedin reconstruction
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Anoxic remineralisation of organic
matter may bias Canth estimates
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TrOCA-MPI
„truth“, MPI Model
0
70
-10
(m
ol-C/kg)
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TrOCA-MPI
Century-scale Trend in PO4 in MPI Model
Negative Canthin deep ocean
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Century-scale trends may bias
Canth estimates
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What about interannual and
decadal variability?
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Internal Variability in AOUs
dv o
f de
cal a
vera
ged
AO
U (
mo
l/kg
)
Frölicher et al., in prep.
5
3
0
2
1
4
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The impact of volcanic forcing on global mean AOU and O2
Frölicher et al., in prep.
100
1500
Dep
th (
m)
-AOU O2
1960 2000 1960 2000Year
Optical Depth
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The impact of volcanic forcing on global meanO2 and AOU
Frölicher et al., in prep.
100
1500
Dep
th (
m)
-AOU O2
1960 2000 1960 2000Year
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.
Internal Variability in DIC and in C* from a control run in top 2000 m
dep
th
(m
ol-
C/k
g)
-4
4
Levine et al., in press
60oS 80oN
1, DIC C*
0
60oS 80oN -15
15
0
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.
Difference between modeled and reconstructed Canth for the C* method
0
-15
15
Levine et al., in press
Modelled increase over 10 year
Difference (model-reconstruction)
60oS 80oN (mol-C/kg)
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Both externally-forced and
internal variability may bias
Canth estimates
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Other potential problems?
• Parameters of reconstruction method have not been determined with model output
• Fixed Redfield ratios assumed in model – correct?
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How do results from different
methods compare with modeled
Canth?
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Reconstruction methods:
• TrOCA (Touratier et al.)
• CT0 (Vazquez-Rodriguez;
adjusted C* method)
• CT0 IPSL: (Lo Monaco; back-calculation method,
uses different preformed relationships for southern and northern water)
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TrOCA
„Truth“: NCAR Model
CT0
IPSL0
70
-10
(m
ol-C/kg)
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Difference between simulated and reconstructed Canth, 20 W,1994
(m
ol-C
/kg)
50
0
-50
Dep
th (
m)
0
5000
60oN80oS
TrOCA
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Difference between simulated and reconstructed Canth, 20 W,1994
(m
ol-C
/kg)
50
0
-50
Dep
th (
m)
0
5000
60oN80oS
CT0
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Difference between simulated and reconstructed Canth, 20 W,1994
(m
ol-C
/kg)
50
0
-50
Dep
th (
m)
0
5000
60oN80oS
IPSL
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Conclusions
• Significant deviations between predicted and reconstructed Canth are found for all methods
• Potential biases: - externally-forced and internal variability- anoxic remineralisation- century-scale trends in watermasses/tracers- deviations from fixed Redfield ratios
- parameters not determined with model output (IPSL Reconstruction Method)
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What ist the impact of
1. temperature distribution2. organic matter export3. CaCO3 export
on DIC and atm. CO2?
Apply a model to discriminate themechanisms
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Dead ocean with T=18oC(present day carbon inventory in ocean-atmosphere system)
Uniform distribution of DICpCO2(atm) = 560 ppm
Atlantic Southern Ocean Pacific
Dep
thD
IC (m
mol/m
3)
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Temperatures in the World Ocean
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1. Solubility and carbon chemistry: cold water holds more DIC than warm water
→ DIC concentration in the (warm) surface are on average depleted with respect to the
(cold) deep ocean
→ atmospheric CO2 is lower compared to an ocean with a uniform temperature of T=18oC
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Dead ocean with present temperature distribution(present-day carbon inventory in ocean-atmosphere system)
Surface water somewhat depleted in DICpCO2(atm) = 439 ppm
Dep
th
Atlantic Southern Ocean Pacific
DIC
(mm
ol/m3)
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2. Marine biota removes carbon from surface waters and this carbon is exported to the deep
→ DIC and nutrient concentrations in the surface are on average depleted with respect to the deep ocean
→ atmospheric CO2 is lower compared to a dead ocean
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The marine organic carbon cycle
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Vertical distribution of tracers in the North Pacific
Redfield ratio:P:N:C:O2 = 1:16:120:-170
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Observed distribution of phosphate
Surface water in the Atlantic and Pacific are depleted in nutrients by biological activities
Dep
th
Atlantic Southern Ocean Pacific
(mm
ol/m3)
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Ocean with organic matter production and temperature distribution (but no calcite production)
Surface water depleted in DICpCO2(atm) = 229 ppm
Dep
th
Atlantic Southern Ocean Pacific
DIC
(mm
ol/m3)
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3. Production and export of CaCO3 increases the partial pressure of CO2 in surface waters
→ A range of marine organisms form shells made of CaCO3
Ca++ + 2 HCO3- → CaCO3 + CO2 + H2O
→ Decrease in DIC, but shift in the ratio between different carbonate species → Alkalinity ~ [HCO3
-]+2 [CO3--] is decreasing
→ [H2CO3*] in the surface and atmospheric CO2 is increased compared to an ocean without calcifying organisms
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Observed distribution of potential Alkalinity
Surface water is depleted in alkalinity
Dep
thP
ot. Alk
(mm
ol/m3)
Atlantic Southern Ocean Pacific
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Observed distribution of DIC
Surface water depleted in DIC and in alkalinitypCO2(atm) = 278 ppm
Dep
thD
IC (m
mol/m
3)
Atlantic Southern Ocean Pacific
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Regulation of atmospheric CO2
Dead ocean with uniform T of 18oC: 560 ppm
Realistic temperature distribution: 439 ppm+ organic matter export 229 ppm+ CaCO3 export 278 ppm
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Greenland and Antarctic temperature, CO2 and CH4 over the last
transition
Stauffer, Monnin, Blunier and co-workers, 2003
Past changes indicate the magnitude of potential future feedbacks
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„Surprises in the Climate System“?
Projected strenght of the North Atlantic overturning
Cubasch et al., 2001
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From the past to the future
Indermühle et al, 1999
NADW collapse: limited impact on atmospheric CO2 and ocean uptake
CO2 varies by up to 20 ppmduring D/O events
WRE1000
Joos et al, 1999; Plattner et al., 2001
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How well can ocean carbon cycle
model simulate the present state?
Selected Results from NCAR CSM1.4-carbon
Thanks to S. Doney, I. Fung, K. Lindsay
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.
Ocean Acidification and Aragonite Saturation
Observation-based
NCAR CSM1.4
su
pe
rsa
turatio
n
A
2
1
4
3
0
A2
1
4
3
0
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.
Observation-based
Aragonite Saturation in the Atlantic
NCAR CSM1.4
sup
ersaturatio
n
0
10
20
-10
CO3— [mol/m3]
1000
4000
0
dep
th [
m]
90oS 90oN
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Export Production of POC
Laws et al. (2000)
Global: 9.2 Pg C
0
100
200
Exp
ort (g
-C m
-2)
CSM1.4
11.1 Pg C
0
100
200
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.
NCAR CSM1.4
Surface Temperature and CO2 for SRES A2 and B1
1900 2000 2100Year
300
500
700C
O2 (
pp
m)
0
1
2
T (
oC
)
A2
B1
A2
B1
Anthropogenic forcing- Fossil and land use CO2 emissions- CH4, N2O, CFCs- direct sulphate aerosols
Natural forcing- solar irradiance- stratospheric volcanic aerosols
1900 2000 2100Year
Instrumental
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Difference 2100 - 1820
Decrease in Export of DOM
1820 -2100
∆ ~ 8 %
1820 2100
Year
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Variability and a decreasing trend in meridional overturning circulation
80oN
Lat
itu
de
40oN
0o
40oS
1820 2000 2100Year
-10
0
10
20
30
Overtu
rnin
g (S
v)
1900
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Long-term CO2 and sea level
committmentin EMICs1820 -2100
2000 2500 3000
2000 2500 3000
Year
60%
60%
0
60%Atmosphere
Ocean
Land
2000 GtC
Thermal Expansion (m)
1
IPCC AR4 EMIC Intercomparison
Plattner et al., 2006;
Cumulative Emissions
0%
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1. Inverse methods such as Ensemble Kalman filtering provide powerful tools for improved estimates of biogeochemical quantities.
It is time to include CARBOOCEAN measurements.
2. Bomb radiocarbon data suggest that the OCMIP air-sea transfer velocity field must be downscaled by ~26%;global mean: 16 cm/hr (Müller et al., 2006, Sweeney, 2006, Ho et al., 2006, Nägler et al., 2006)
It is time to use a downscaled transfer velocity
3. Simulations with forced and internal variability available
It is time to analyse internal and externally-forced variability
Conclusions
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CSM1.4-carbonFossil only
Sabine et al. (2003)
CO2 [mol/m2]
Column Inventory of anth. CO2
1994
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A Historical Perspective
Siegenthaler and Oeschger, Science, 1978:
“With climate models becoming more and more realistic, a maximum permissible atmospheric CO2 level might be found which should not be exceeded if the atmospheric radiation balance is not to be disturbed in a dangerous way. … This scenario clearly does not allow us to go on burning fossil fuel at the present growth rate for a long time … Around the turn of the century new technologies would have to take over a substantial part of global energy production.”
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Atmospheric Increase and Fossil Emissions
IPCC, Chap 7, 2007
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Fraction of Fossil Emissions Staying Airborne
IPCC, Chap 7, 2007
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Evaluating the overall impact in a probabilistic way
SRES B1
Knutti et al, 2003
Higher CO2 under global warming leads toan increased probability for high warming