Estimated Sources and Sinks of Carbon Monoxide (Tg CO per year)

	WMO (1985)	Seiler & Conrad (1987)	Khalil & Rasmussen (1990)	Crutzen & Zimmerman (1991)
Primary Sources
Fossil Fuel	440	640±200	400-1000	500
Biomass Burning	640	1,000±600	335-1400	600
Plants	-	75±25	50-200	-
Oceans	20	100±90	20-80	-
Secondary Sources
NMHC Oxidation	660	900±500	300-1,400	600
Methane Oxidation	600	600±300	400-1,000	530
Sinks
OH Reaction	900±700	2,000±600	2,200	2,050
Soil Uptake	256	390±140	250	280
Stratospheric Oxidation	-	110±30	100	-

Adapted from Houghton, J.T., Climate Change 1992. Cambridge University Press.