First satellite identification of volcanic carbon monoxide

Volcanic degassing produces abundant H₂O and CO₂, as well as SO₂, HCl, H₂S, S₂, H₂, HF, CO, and SiF4. Volcanic SO₂, HCl, and H2S have been detected from satellites in the past; the remaining species are analyzed in situ or using airborne instruments, with all the consequent limitations in safety and sampling, and at elevated costs. We report identification of high CO concentrations consistent with a volcanic origin (the 2010 Eyjafjallajökull and 2011 Grímsvötn eruptions in Iceland) in data from the Measurements of Pollution in the Troposphere instrument (MOPITT) onboard EOS/Terra. The high CO values coincide spatially and temporally with ash plumes emanating from the eruptive centers, with elevated SO₂ and aerosol optical thickness, as well as with high CO values in data from the Infrared Atmospheric Sounding Interferometer (IASI), onboard MetOp-A. CO has a positive indirect radiative forcing; climate models currently do not account for volcanic CO emissions. Given global volcanic CO₂ emissions between 130 and 440 Tg/year and volcanic CO:CO₂ ratios from the literature, we estimate that average global volcanic CO emissions may be on the order of ~5.5 Tg/year, equivalent to the CO emissions caused by combined fossil fuel and biofuel combustion in Australia.