Transcript coupled - jamstec

Quasi-inversion estimation of
permissible CO2 emission
toward stabilization
Toru Miyama
（Frontier Research Center for Global Change）
2007 October 11
Forward Casting
(conventional projection)
“What if ?”
CO2 emission
CO2 in air
Temp. rise
Backward Casting (Inverse)
(social/political needs)
“How ?”
Permissible
CO2 emission
CO2
stabilization
Temperature
target
CO2 emission
= Nature uptake
??
~2oC?
Climate-change Carbon-cycle
Feedback
Anthropogenic
CO2 emission
CO2
increase
in air
Uptake by ocean and land
• Part (about half at present) of anthropogenic CO2 is absorbed by
nature (ocean and land). The rest remains in atmosphere.
• Climate change projections with carbon-cycle models tell that
nature uptake would decrease more or less due to temperature
rise. Reduced CO2 uptake results in more CO2 concentration, and
hence higher temperature (Climate-change Carbon-cycle
feedback is positive.)
• Therefore, further CO2 emission cut would be needed for the
same CO2 stabilization target under the influence of Climatechange Carbon-cycle feedback
Invitation to “Cool Earth 50”
By ex-PM Abe (May 24, 2007)
Half
emission
Same level
as nature
uptake
stabilization
“Quasi-inverse estimation”
Proposed for AR5 （Hibbard et al. 2007）
Climate model with carbon cycle model
CO2 stabilization
scenario (given)
Projection of climate
by the model
Projection of CO2
land/ocean uptake
under the influence of
climate change and given
CO2 concentration
Permissible Emission =
d
(CO2
dt
in air)
+ Ocean/Land Uptake
Method and Model
Integrated Earth System Model
• MIROC “-KISSME”
• Ocean: NPZD biology model（Oschlies,2001）+
carbon cycle recommended by OCMIP.
• Land: Sim-CYCLE model (Ito and Oikawa,
2002).
• Intermediate Climate-change Carbon-cycle
feedback strength among AR4 models
Model integration
• CO2 stabilization scenario (Knutti et al. 2005)
CO2 concentration time-series (ppm)
SP1000
（1000ppm at mid-24 century）
SP550
（550ppm at mid-22 century）
• Other forcings
year
– Other greenhouse gasses、aerosol、vegetation index: the same
conditions as ones for year 1850
• Time integration
– 250 years spin-up under year 1850 conditions
– Integration from 1850 to 2300 under given CO2 scenario
Climate-change Carbon-cycle Feedback
• To test influence of Climate-change Carbon-cycle
Feedback, 2 runs with/without greenhouse effect are
performed for each scenario (SP550, SP1000).
2x2=4 runs in total
CO2 concentration CO2 for radiation
SP550
coupled
SP550
SP550
SP550
uncoupled
SP550
constant
SP1000
coupled
SP1000
uncoupled
SP1000
SP1000
SP1000
constant
No greenhouse effect
No greenhouse effect
Results
30 year running average to remove
seasonal/ interannual /decadal variation
Global-average T2/SST time-series
T2
SST
SP1000 coupled
SP1000 coupled
SP550 coupled
SP1000 uncoupled
SP550 uncoupled
（K; deviation from 282.2K)
SP550 uncoupled
SP550 uncoupled
SP 1000 uncoupled
（K; deviation from 290.15K)
• More CO2 , More temperature rise, in the coupled runs.
• No temperature rise for the uncoupled runs.
• Gradual temperature rise even after CO2 stabilization (SP550 coupled)
• ~3oC T2 rise for SP550 coupled
Ocean/Land CO2 uptake (PgC/year)
SP550
TOTAL
Ocean
Land
SP1000
Solid：Coupled
dashed：Uncoupled
• CO2 uptake increases during accelerated CO2 concentration. Then, slowdown
of CO2 rise reduces uptake toward equilibrium. Ocean needs longer time for
equilibrium than land. Eventually ocean uptake dominates in total uptake.
• Climate-Change Carbon-Cycle Feedback reduces uptake. Especially
influence to land uptake is significant. In SP1000 coupled run, Land becomes
net source of CO2.
Permissible Emission = dtd (CO2 in air)
+ Ocean/Land Uptake
PgC/year
SP550
SP1000
dashed： Uncoupled
run
solid:
Coupled run
Green:
Fossil carbon emission
(reality)
• Stabilization of CO2 and the accompanying nature adjustment toward
equilibrium force reduction of permissible emission. Slow adjustment of ocean
allows anthropogenic emission even at year 2300.
• Climate-change Carbon-Cycle feedback reduces permissible emission.
• Quasi-inversion estimate agrees well with fossil carbon emission during 20th
century.
Cumulative Sum from 1850 to 2300
(PgC)
SP550
Land uptake
Ocean Uptake
Total uptake Emission
coupled
480.7
708.3
1189
1766
uncoupled
165.4
(-65%)
599.9
(-15.3%)
765.3
(-35.6%)
1342
(-24.0%)
Land uptake
Ocean uptake
Total uptake
Emission
1153
937.2
(-18.7%)
1608.8
891.2
(-44.6%)
3127
2411
(-22.9%)
SP1000
coupled
455.8
uncoupled -46.0
(-110.1%)
30年移動平均なし(年平均のみ）
Ocean Uptake
Land Uptake
Total uptake
Emission
Climate-change
Carbon-cycle
feedback
in ocean
SP550 as an example
“Coupled run” minus “uncoupled run”
Feedback to CO2 flux (global total)
(“coupled run” minus “uncoupled run”）
CO2 flux＝E (pCO2a-pCO2o）
μatm (Global average）
PgC/year
Why pCO2o is increased
by feedback?
pCO2o=P(T,S,TCO2,Alk)
Temperature, salinity, TCO2, alkalinity
dependence
Year 2300
Year 2100
More Temperature rise,
SST increase
Is important
Reduced TCO2
Feedback in spatial distribution
(“coupled run” minus “uncoupled run”）
Accumulated CO2 flux
From 1850 to 2100
increase
decrease
KgC/m^2
pCO2o
(1850-2100 average)
(“coupled run” minus “uncoupled run”）
pCO2o
Each contribution
T
TCO2
S
Alkalinity
Balance on land
Balance for total
SP550
SP1000
GPP
total
veg res.
soil res
Solid:coupled
Dash:uncoupled
Balance for veg
SP550
SP1000
GPP
total
veg res.
litter fall
Solid:coupled
Dash:uncoupled
Balance for soil
SP550
SP1000
GPP
total
veg res.
litter fall
Solid:coupled
Dash:uncoupled
Summary
• Climate-change Carbon-cycle feedback reduces
permissible emission. Total reduction of the
accumulated CO2 emission to 2300 is about 20%.
• If SP550 is the target, 50% reduction until year 2050
is not necessary. However, it results in ~3oC
temperature rise. In any way, much further reduction
of CO2 is necessary for final stabilization.
• Land relatively quickly adjusts to equilibrium.
Furthermore, global warming could change land to
CO2 source. Land would not be reliable CO2 sink in
the long run..
• Because ocean needs long time to equilibrium, it can
be sink of CO2 for long time. Climate-change
Carbon-cycle is positive, but relatively small.
Discussions
• Other green gasses, aerosols, land use change must
be considered (Any stabilization target?).
• SP550 might be too relaxed target.
• Forward experiments with 50% Greenhouse gas
until 2050 are being considered (with
Masui/Hijioka-san in NIES. )
forward
Emission
concentration
Quasi-inversion
Stabilization Scenario
NADW strength