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Workshop on common metrics to calculate the CO2 equivalence of anthropogenic greenhouse gas emissions by sources and removals by sinks. Radiative Forcing and Global Warming Potentials due to CH 4 and N 2 O. Hua Zhang Ruoyu Zhang. National Climate Center. China Meteorological Administration.

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Radiative Forcing and Global Warming Potentials due to CH 4 and N 2 O

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Workshop on common metrics to calculate the CO2 equivalence of anthropogenic greenhouse gas emissions by sources and removals by sinks

Radiative Forcing and Global Warming Potentials due to CH4 and N2O

Hua Zhang Ruoyu Zhang

National Climate Center

China Meteorological Administration

April 3-4, 2012

Bonn, Germany


Outline

Backgrounds

1

Data & Methods

2

2

Radiative forcings

3

GWPs& GTPs

4

Discussion

5


CH4 (pptv)

C02 (ppmv)

N20 (pptv)

Backgrounds

Concentrationsof main GHGs before 2005

10000 5000 0

year(before 2005)


Concentrationsof main GHGs under SRES scenarios


Backgrounds

气候变化的一种机制

通过辐射传输过程


Methods

Radiative forcing (RF)


Time-decaying functions

RF of CO2

Radiative efficiency

Methods

GWP

RF of GHG x

1 GWP is related to emission process of GHG;

2GWP 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.


Surface temperature changes

Methods

GTP

Tchanges with time

T arrives at balance not varying

  • 1 GTP refers to emission process of GHGs too ;

  • 2 GTP can convert any kind of GHGs equivalently to

  • CO2 emission too;

  • GTP denotes the effect of GHG on the temperature

  • changes of the earth-atmosphere system.


Model & Data

Radiative Transfer Model

(Zhang et al., 2003; 2006a,b)

  • 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 498bandswith intervals of 5cm-1


Model & Data

辐射传输模式

Gas molecular spectrum data

辐射传输模式

辐射传输模式

辐射传输模式

辐射传输模式

HITRAN2004

Atmosphereprofiles data

6kinds of typical model atmosphere :

TRO、MLS、MLW、SAS、SAW、USS

Clouds

ISCCP D2 products


Criterion: to judge whether the system reaches to balance

Iteration to calculate ARF

Temperature profile T0(L)

kn=0

Radiative Transfer Model

(Zhang et al.,2006)

Radiative Transfer Model

(Zhang et al.,2006)

Heating rate for zero concentration: htr0(L)

Heating rate for 0.1 ppbvconcentration: htr1(L)

iterationkn=kn+1

kn=0

Instantaneous RF

Heating rate

Htrdif(L)=htr1(L) - htr0(L)

htrdif(L)<ξ

N

Tnew(L)=Told(L)+htrdif(L)×△t

L:from Tropopause to TOA

Y

Adjusted RF


Model tests

(1)CO2concentration is doubled from 287 ppmvto 574 ppmv;

(2)With doubled CO2 concentration (574 ppmv), H2O content is increased by 20% of its concentration of 1860year


Results

Radiative efficiency

* unit:W·m-2·ppbv-1

** Lifetime : CO2 : 120a ; CH4 : 12a ; N2O : 114a


Results

Radiative forcings (ARF)

* unit:W·m-2

** Lifetime : CO2 : 120a ; CH4 : 12a ; N2O : 114a


Results

Climate sensitivity parameter : λ

Its typical value is chosen as 0.5K·(W·m-2)-1

Original concentration of CO2 : 385.2 ppmv

Then:

IPCC : 1.5~4.5K


Results

ARF fittingformula

C : CO2concentration;

C0 : background CO2 concentration,

C0 = 385.2 ppmv;

fitting parameters : α=6.2554, β=5.2783×10-2


Results

6种大气廓线下

ARF fitting formula

CH4background 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 concentrationN0=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


Results

Test of fitting

* Shi et al., absolute error≤0.05 W m-2


Results

before atmospheric lifetime adjustment

after atmospheric lifetime adjustment


Results

For comparison :

Shine(2005)results


After the lifetime-adjustment


Results

Before atmospheric lifetime adjustment

After atmospheric lifetime adjustment


Results


AGTPP of CH4&N2O

AGTPS of CH4& N2O


AGTPP of CO2

Temperature changes (10-16K)

Temperature changes (10-14K)

Time (a)

AGTPS of CO2

Time (a)


Discussion

The lifetimes of CH4are relatively short-lived GHGs; GWPgreatly over-estimatesthe 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!


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