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

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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  1. 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

  2. Outline Backgrounds 1 Data & Methods 2 2 Radiative forcings 3 GWPs& GTPs 4 Discussion 5

  3. CH4 (pptv) C02 (ppmv) N20 (pptv) Backgrounds Concentrationsof main GHGs before 2005 10000 5000 0 year（before 2005）

  4. Concentrationsof main GHGs under SRES scenarios

  5. Backgrounds 气候变化的一种机制 通过辐射传输过程

  6. Methods Radiative forcing (RF)

  7. 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.

  8. 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.

  9. 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

  10. 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

  11. 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

  12. 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

  13. Results Radiative efficiency * unit：W·m-2·ppbv-1 ** Lifetime : CO2 : 120a ; CH4 : 12a ; N2O : 114a

  14. Results Radiative forcings (ARF) * unit：W·m-2 ** Lifetime : CO2 : 120a ; CH4 : 12a ; N2O : 114a

  15. 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

  16. Results ARF fittingformula C : CO2concentration; C0 : background CO2 concentration, C0 = 385.2 ppmv; fitting parameters : α=6.2554, β=5.2783×10-2

  17. 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

  18. Results Test of fitting * Shi et al., absolute error≤0.05 W m-2

  19. Results before atmospheric lifetime adjustment after atmospheric lifetime adjustment

  20. Results For comparison : Shine（2005）results

  21. After the lifetime-adjustment

  22. Results Before atmospheric lifetime adjustment After atmospheric lifetime adjustment

  23. Results

  24. AGTPP of CH4&N2O AGTPS of CH4& N2O

  25. AGTPP of CO2 Temperature changes (10-16K) Temperature changes (10-14K) Time (a) AGTPS of CO2 Time (a)

  26. 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.

  27. 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.

  28. Thanks！

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