Somewhere between two and five billion tons of CO enter the atmosphere each year as a byproduct of fossil fuel combustion and biomass burning and through natural emissions from plants. Natural and human-related emissions appear to be roughly equal. As the data analysis becomes more sensitive, it should reveal CO emissions from heavily polluted cities as well. Near the earth's surface, CO is a deadly poison when highly concentrated. Because of its high reactivity, short lifetime, and low concentration, OH can't be measured from space, but monitoring CO will open the window to understanding the cleansing processes and their implications for pollution levels.
Carbon monoxide is also an excellent tracer for observing global transport in the troposphere.
Its lifetime of two months is long enough for the gas to be tracked as it rises from the surface and journeys around the globe, yet short enough to prevent it from mixing evenly in the atmosphere, which would obscure its sources and paths. Tracking CO from space is a key to observing how pollution from one continent can reach and adversely affect another, reminding us that we have the capacity to pollute the globe. With plenty of time to mix evenly around the globe, its sources and tracks are difficult to unravel. Though there's only a half billion tons of it, the gas absorbs infrared radiation emitted by the earth 60 times more efficiently than carbon dioxide does. But delays for the instrument were not yet over.