Radiative Forcing and Global Warming Potentials due to CH4 and N2O
Hua Zhang Ruoyu ZhangNational Climate Center
China Meteorological Administration
April 3-4, 2012
Bonn, Germany
Workshop on common metrics to calculate the CO2 equivalence of anthropogenic
greenhouse gas emissions by sources and removals by sinks
Backgrounds
Data & Methods
Radiative forcings
GWPs & GTPs
Discussion
2
4
3
5
2
1
10000 5000 0
year （ before 2005）
C0
2 (p
pm
v)
CH
4 (p
ptv
)N
20 (
pp
tv)
Concentrations of main GHGs before 2005
Concentrations of main GHGs under SRES scenarios
气候变化的一种机制
通过辐射传输过程
TH
r
TH
x
TH
r
TH
x
x
dttra
dttxa
dttRF
dttRF
GWP
0
0
0
0
)]([
)]([
)(
)(
1 GWP is related to emission process of GHG;2 GWP can convert any kind of GHG equivalently to CO2 emission, which makes the comparison easily
among different gases;3 GWP denotes the cumulative climate effect of the GHG during a period of time.
RF of GHG x
RF of CO2 Radiative efficiency
Time-decaying functions
1 GTP refers to emission process of GHGs too ;
2 GTP can convert any kind of GHGs equivalently to
CO2 emission too;
3 GTP denotes the effect of GHG on the temperature
changes of the earth-atmosphere system.
)(
)()( tT
tFdt
tTdC
THr
THxTH
x T
TGTP
FT
T changes with time Surface
temperature changes
T arrives at balance not varying
• 998-band longwave radiative transfer
scheme (high resolution)• 10~49000cm-1 (0.2~1000µm) is divided into 998
bands
• longwave region 10~2500cm-1(4~1000µm） is 498 bands with intervals of 5cm-1
Radiative Transfer Model(Zhang et al., 2003; 2006a,b)
6 kinds of typical model atmosphere :
TRO 、 MLS 、 MLW 、 SAS 、 SAW 、 USS
HITRAN2004
辐射传输模式辐射传输模式辐射传输模式辐射传输模式辐射传输模式Gas molecular spectrum data
Atmosphere profiles data
Clouds
ISCCP D2 products
htrdif （ L ） <ξ
N
Y
Radiative Transfer Model (Zhang et al. ， 2006)
Heating rate for zero concentration: htr0(L)
Heating rate Htrdif （ L ） =htr1(L) - htr0(L)
Tnew （ L ） =Told （ L ）+htrdif （ L ） × t △
L ： from Tropopause to TOA
Adjusted RF
Heating rate for 0.1 ppbv concentration: htr1(L)
Temperature profile T0(L)
Radiative Transfer Model (Zhang et al. ， 2006)
iterationkn=kn+1
kn=0
Instantaneous RF
kn=0Criterion: to judge whether the system reaches
to balance
（ 1 ） CO2 concentration is doubled from 287 ppmv
to 574 ppmv；（ 2 ） With doubled CO2 concentration (574 ppmv),
H2O content is increased by 20% of its concentration
of 1860 year
Doubled CO2
Doubled CO2 , H2O increase by 20%
Model layer
998-band
AOGCMs LBL 998-band AOGCMs LBL
TOM 3.03 2.45 2.8 3.26 3.75 3.78
200 hPa 5.6 5.07 5.48 4.13 4.45 4.57
Surface 1.7 1.12 1.64 11.14 11.95 11.52
GasClear sky Cloudy sky
IPCC2007
IRE ARE AREARE after lifetime-
adjustmentARE
CO2 1.99E-5 1.88E-5 1.64E-5 1.57E-5, +11.9% 1.4E-5
CH4 5.13E-4 5.06E-4 4.14E-4 3.73E-4, +0.8% 3.7E-4
N2O 3.87E-3 3.79E-3 3.13E-3 2.98E-3, -1.4% 3.03E-3
* unit ： W·m-2·ppbv-1
** Lifetime : CO2 : 120a ; CH4 : 12a ; N2O : 114a
Radiative efficiency
Gas
2005 2010IPCC
2007before
adjustmentAfter
adjustmentBefore
adjustmentAfter
adjustment
CO2 1.89 1.81 2.04 1.95 1.66±0.17
CH4 0.581 0.523 0.583 0.525 0.48±0.05
N2O 0.185 0.177 0.187 0.179 0.16±0.02
* unit ： W·m-2
** Lifetime : CO2 : 120a ; CH4 : 12a ; N2O : 114a
Radiative forcings (ARF)
Climate sensitivity parameter : λ
Its typical value is chosen as 0.5K·(W·m-2)-1
Original concentration of CO2 : 385.2 ppmv
Then: FT
ConcentrationARF
/ W m-2
TemperatureChanges / K
CO2×1.5 2.8 1.4
CO2×2.0 4.8 2.4
CO2×2.5 6.4 3.2
CO2×3.0 7.8 3.9
CO2×3.5 9.0 4.5
CO2×4.0 9.8 4.9
IPCC :
1.5~4.5K
)()/ln( 002CCCCARFCO
C : CO2 concentration;
C0 : background CO2 concentration,
C0 = 385.2 ppmv;
fitting parameters : α=6.2554, β=5.2783×10-2
ARF fitting formula
0 400 800 1200 1600
CO2 Concetration (ppmv)
-4
0
4
8
12
CO
2 A
RF
(W
m-2
)Original
Fitting
6 种大气廓线下
CH4 background concentration M0=1797ppbv;
0≤M0,N0≤10000 ppbv ;
fitting parameters : α=0.03195, β=1.439×10-4, γ=-1.133×10-3, δ=1.221×10-7
N2O background concentration N0=321.8ppbv
0≤M0,N0≤10000 ppbv;
fitting parameters : α=0.08801, β=0.0011 γ=-3.7167×10-4, δ= 2.0116×10-9
)()()()( 00004MMNMMNMMMMARFCH
)()()()( 00002NNMNNMNNNNARF ON
ARF fitting formula
Test of fitting
Test issueModel results
/ W m-2
Formula results/ W m-2
Absoluteerror
/ W m-2
CO2×2 + CH4×2 + N2O×2 6.07 6.05 0.02
CO2×2 + CH4×1 + N2O×1 4.70 4.76 0.06
CO2×2 + CH4×2 + N2O×1 5.36 5.30 0.06
CO2×1 + CH4×2 + N2O×2 1.32 1.29 0.03
* Shi et al., absolute error≤0.05 W m-2
GasGWP
GWPIPCC 2007
GTPP GTPS
20 / 100 / 500 20 / 100 / 500 20 / 100 / 500 20 / 100 / 500
CH4 50 / 17 / 5.3 72 / 25 / 7.6 41 / 0.26 / ~0 56 / 19 / 5.4
N2O 258 / 265.7 / 137 289 / 298 / 153 268 / 233 / 11 250 / 269 / 139
after atmospheric lifetime adjustment
before atmospheric lifetime adjustment
气体GWP
GWPIPCC 2007
GTPP GTPS
20 / 100 / 500 20 / 100 / 500 20 / 100 / 500 20 / 100 / 500
CH4 47 / 16 / 5 72 / 25 / 7.6 39 / 0.24 / ~0 53 / 18 / 5
N2O 257 / 266 / 136 289 / 298 / 153 268 / 233 / 11 250 / 268 / 138
Gas
Analytical calculation EBM
GTPP GTPS GTPP GTPS
20 / 100 / 500 20 / 100 / 500 20 / 100 / 500 20 / 100 / 500
CH4 52 / 0.35 / 0 69 / 24 / 7 46 / 5 / 0.8 66 / 25 / 8
N2O 290 / 270 / 13 260 / 290 / 160 290 / 270 / 35 270 / 290 / 160
Shine （ 2005 ） results
For comparison :
GasAtmosphere
lifetime /a
AGWP / 10-14·W·m-2·kg-1
20 / 100 / 500
CO2 120 2.72 / 9.57 / 31.5
CH4 12 127.7 / 157.3 / 157.4
N2O 114 700.3 / 2542 / 4298
HFC-32 4.9 6613 / 6727 / 6727
HFC-125 29 19971 / 38808 / 40083
HFC-134 10 12962 / 14990 / 14991
HFC-134a 14 12320 / 16191 / 16204
HFC-143a 52 24107 / 64468 / 75499
HFC-152a 1.4 1573 / 1573 / 1573
C2F6 10000 28168 / 140277 / 68757
CF4 50000 12527 / 62553 / 311520
SF6 3200 52193 / 257734 / 1211774
After the lifetime-adjustment
GasAGTPP / 10-16·K·kg-1 AGTPS / 10-14·K·kg-1
20 / 100 / 500 20 / 100 / 500
CH4 372 / 1.62 / ~0 73.8 / 139.5 / 139.7
N2O 2419 / 1465 / 43.9 328.9 / 1972 / 3593
CO2 9.04 / 6.28 / 3.89 1.31 / 7.34 / 25.9
After atmospheric lifetime adjustment
Before atmospheric lifetime adjustment
GasAGTPP / 10-16·K·kg-1 AGTPS / 10-14·K·kg-1
20 / 100 / 500 20 / 100 / 500
CH4 336 / 1.46 / ~0 66.5 / 125.7 / 125.9
N2O 2312 / 1401 / 41.9 314 / 1884 / 3434
CO2 8.64 / 6.01 / 3.72 1.26 / 7.02 / 24.8
GasAGTPP / 10-16·K·kg-1 AGTPS / 10-14·K·kg-1
20 / 100 / 500 20 / 100 / 500
HFC-32 16834 / 10.2 / ~0 5209 / 7118 / 7119
HFC-125 80622 / 7321 / 0.008 12550 / 40266 / 42393
HFC-134 35691 / 59.9 / ~0 8093 / 14012 / 14021
HFC-134a 44445 / 361 / ~0 8322 / 17108 / 17160
HFC-143a 46423 / 12837 / 5.9 13945 / 62032 / 75986
HFC-152a 2755 / 1.5 / ~0 1376 / 1669 / 1669
C2F6 124990 / 146336 / 140610 16213 / 131366 / 705206
CF4 51547 / 60720 / 60241 6683 / 143168 / 296248
SF6 233196 / 268627 / 237083 30283 / 243422 / 1253570
0 100 200 300 400 500
Time (a)
0
50
100
150
200
250
Tem
pera
ture
Ch
ang
e (
10
-15 K
) N2O
N2O ( life-adjusted )
CH4
CH4 ( life-adjusted )
AGTPS of CH4 & N2O 0 100 200 300 400 500
Time (a)
0
100
200
300
400
Tem
pera
ture
Cha
nge
(10-1
3 K)
N2O
N2O ( life-adjusted )
CH4
CH4 ( life-adjusted )
AGTPP of CH4 & N2O
AGTPS of CO2
AGTPP of CO2
0 100 200 300 400 500
/年份 a
3
4
5
6
7
8
9
10温
度/1
0-1
6K
AGTPP
adjustedAGTPP
Tem
per
atu
re c
han
ges
(10
-16
K)
0 100 200 300 400 500
/年份 a
0
4
8
12
16
20
24
28
温度
/10-1
4K
AGTPS
adjustedAGTPS
Tem
per
atu
re c
han
ges
(10
-14
K)
Time (a)
Time (a)
The lifetimes of CH4 are relatively short-lived
GHGs; GWP greatly over-estimates the effects of their pulse emission on climate changes.
GTPp is an optimal metric for assessing the long-term effects of CH4 emissions on global
climate change, by considering practical emissions of these gases.
• Climate sensitivity parameter λ can affect AGWP and AGTP greatly, this should be considered as a large uncertainty in estimating process.
• AGWPs and AGTPs of long-lived GHGs are sensitive to time horizon; while AGTPp of short-lived GHGs is sensitive to time horizon greatly.
• Clouds is another large factor of uncertainties in estimating GWP or GTP
and should be clarified in IPCC AR5 report.
Thanks！
