quasi-inversion estimation of permissible co 2 emission toward s tabilization
Post on 12-Jan-2016
35 Views
Preview:
DESCRIPTION
TRANSCRIPT
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 ?”
Temp. riseCO2 emission CO2 in air
Backward Casting (Inverse)(social/political needs)
“How ?”
??
PermissibleCO2 emission
Temperaturetarget
~2oC?
CO2 stabilization
CO2 emission= Nature uptake
Climate-change Carbon-cycle Feedback
Anthropogenic
CO2 emission
Uptake by ocean and land
CO2increase
in air
• 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 Climate-change 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”
Permissible Emission = (CO2 in air) + Ocean/Land Uptake
Proposed for AR5 ( Hibbard et al. 2007 )
Climate model with carbon cycle model
CO2 stabilizationscenario (given)
Projection of climateby the model
Projection of CO2 land/ocean uptake under the influence ofclimate change and given CO2 concentration
dt
d
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)
• Other forcings– Other greenhouse gasses 、 aerosol 、 vegetation index: the same cond
itions as ones for year 1850• Time integration
– 250 years spin-up under year 1850 conditions– Integration from 1850 to 2300 under given CO2 scenario
CO2 concentration time-series (ppm)
SP550( 550ppm at mid-22 century )year
SP1000( 1000ppm at mid-24 century )
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
coupledSP550 SP550
SP550
uncoupledSP550 constant
No greenhouse effect
SP1000
coupledSP1000 SP1000
SP1000
uncoupledSP1000 constant
No greenhouse effect
Results
30 year running average to remove seasonal/ interannual /decadal variation
Global-average T2/SST time-series
SP1000 coupled
SP550 coupled
T2
SP1000 uncoupledSP550 uncoupled
SP1000 coupled
SP550 uncoupled
SP550 uncoupledSP 1000 uncoupled
SST
( K; deviation from 282.2K) ( 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 SP1000TOTALOceanLand
Solid : Coupleddashed : 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 = (CO2 in air)
+ Ocean/Land Uptake
dashed : Uncoupled run
SP550 SP1000
• 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.
PgC/year
Green: Fossil carbon emission (reality)
solid:Coupled run
dt
d
Cumulative Sum from 1850 to 2300 (PgC)
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
coupled 455.8 1153 1608.8 3127
uncoupled -46.0
(-110.1%)
937.2
(-18.7%)
891.2
(-44.6%)
2411
(-22.9%)
SP550
SP1000
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 )
PgC/year
μatm (Global average )
Why pCO2o is increased by feedback? pCO2o=P(T,S,TCO2,Alk)
Temperature, salinity, TCO2, alkalinitydependence
SST increaseIs important
More Temperature rise,
Reduced TCO2
Year 2100 Year 2300
Feedback in spatial distribution (“coupled run” minus “uncoupled run” )
Accumulated CO2 fluxFrom 1850 to 2100increase
KgC/m^2
decrease
pCO2o(1850-2100 average)
pCO2o
(“coupled run” minus “uncoupled run” )
Each contribution
T S
TCO2Alkalinity
Balance on land
Balance for total
SP550 SP1000
soil res
veg res.
total
GPP
Solid:coupledDash:uncoupled
Balance for veg
SP550 SP1000
litter fall
veg res.
total
GPP
Solid:coupledDash:uncoupled
Balance for soil
SP550 SP1000
litter fall
veg res.
total
GPP
Solid:coupledDash: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. )
Emission concentration
forward
Quasi-inversion
Stabilization Scenario
NADW strength
top related