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！