Potency of Greenhouse Molecules 32 nd Conf. Climate - - PowerPoint PPT Presentation

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Potency of Greenhouse Molecules 32 nd Conf. Climate Variability/Change American Meteorological Society Phoenix, USA Jan. 7, 2019 W. A. van Wijngaarden (York, Canada) & W. Happer (Princeton, USA) www.wvanwijngaarden.info.yorku.ca

SLIDE 1

Potency of Greenhouse Molecules

32nd Conf. Climate Variability/Change American Meteorological Society Phoenix, USA

Jan. 7, 2019
W. A. van Wijngaarden (York, Canada)

& W. Happer (Princeton, USA) www.wvanwijngaarden.info.yorku.ca

SLIDE 2

Greenhouse Gas Transitions

Line Strengths from Hitran Database

H2O N2O CH4 CO2 O3

SLIDE 3

CO2 Bending Mode

at T = 300 K & P = 1 atm.

Voigt Lineshape Wing Suppressed Lineshape

Atmosphere opaque at line center → global warming driven by far wings of lineshape
Far wings fall off faster than Voigt profile due to Dicke narrowing & collisions

SLIDE 4

Altitudinal Dependence

Temperature Number Density

McClatchey et al. Env. Res. Pap., AFCRL-782-0497 (1972)

SLIDE 5

Schwarzschild Equation

S. Chandrasekhar, Radiative Transfer, Dover, New York (1960)

Upward infrared heat intensity I(ν, z) at frequency ν & height z given by where attenuation Planck Brightness Stefan Boltzmann Law

CO2, N2O, CH4, H2O, O3

SLIDE 6

Model Intensity Comparison to Satellite Data

R. Hanel et al, Geophys. Res. 77, 2629 (1972)
Intensity calculation for 1971 ambient levels of CO2, CH4, N2O & O3

a) Sahara Model b) Sahara Observations c) Antarctica Model d) Antarctica observations

H2O CO2 O3 N2O, CH4 H2O CO2

-- B(320 K)
-- B(190 K)

SLIDE 7

Upwards Flux at various Frequencies

H2O CO2 O3 500.5 cm-1 667.4 cm-1 971 cm-1 1016.2 cm-1 ρ∞ = 2.3 ρ∞ = 51688 ρ∞ = 0.033 ρ∞ = 7.11

100 80 60 40 20

Altitude (km)

0.0 0.5 1.0 0.0 0.5 1.0 0.0 0.5 1.0 0.0 0.5 1.0

SLIDE 8

Radiative Forcing

Net Upwards Flux (W/m2) Altitude (km)

Fluxes computed for surface at 288.7 K & standard temperature profile
Standard Surface Levels: CO2 (400 ppm), CH4 (1.8 ppm ), N2O (0.32 ppm)
Standard Surface H2O (7750 ppm) varied ±6%
O3 (7.8 ppm at 35 km) kept constant
- Doubled
- Standard
- Halved
- Transparent

SLIDE 9

Forcing: ΔZ = Z(Standard) – Z(Doubled) Temperature Increase: ΔT = ΔZ T 4 Z

Gas Concentration Change Top of Atmosphere Forcing (W/m2) H2O +6% corresponding to 1 oC 0.9 CO2 400 → 800 ppm 4.0 CH4 1.8 → 3.6 ppm 1.5 N2O 0.32 → 0.64 ppm 2.2 O3 No Change Total All of above 5.3 ⇒ ΔT = +1.4 oC Plus Clouds, Aerosols ????

Temperature Change due to Forcing

SLIDE 10

Greenhouse Gas Potency Pi (Ni, Nj) = δ F / δ Ni

Gas i Column Density (m-2) Power per Molecule Pi(Ni, Nj) (10-22 W) Pi(0, 0) Pi(0, Ns) Pi(Ns, Ns) H2O 4.67 x 1026 1.5 1.2 2.5 x 10-4 CO2 8.61 x 1025 3.5 2.5 4.9 x 10-4 O3 9.22 x 1022 5.7 4.6 0.38 N2O 6.61 x 1022 2.2 0.91 0.20 CH4 3.76 x 1023 0.71 0.27 2.6 x 10-2

10 0.5 1 1.5 2 Forcing Change (W/m2)

f = Ni / Nsi H2O CO2 O3 N2O CH4

SLIDE 11

Conclusions

1. Radiative Forcing

Doubling CO2, CH4, N2O & increasing H2O gives 5.3 W/m2 forcing.

2. Temperature Increase

Preceding forcing gives ∼1.5 oC temperature increase. This is crude estimate as it doesn’t consider changes in convection or clouds.

3. Greenhouse Potency
At very low concentrations, CO2, CH4, N2O & H2O have

comparable forcings

At ambient levels CH4 & N2O have greater per molecule forcing