Trends in the atmospheric methane burden

Parker Kraus

Methane emissions

Methane measurement network

CH4 CH3 CH3O2

CH3OOH

CH3O

CH2O CHO COOH O2, MNO

HO2 OH

O2

hv

hv, O2

OH

OH

O2

hv

Methane oxidation

In clean troposphere, ~70% of OH reacts with CO, 30% with CH4

“Bottom up” estimation of methane emission

Growth rate of atmospheric methane (ppb/yr)

Figure by Ken Masarie

Methane emissions

Methane emission from terrestrial vegetation

Atmospheric constraint

Scaling by biomass instead of NPP

In summary:• The decreasing rate of atmospheric methane

accumulation remains mysterious.

• The most significant drivers of atmospheric methane concentrations, wetland emissions and OH concentrations, are poorly constrained.

• Tropical fires and Arctic warm anomalies produce (relatively) clear signals.

• I don’t think terrestrial plants emit methane.

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