Global carbon monoxide concentrations, MOPITT data. The data show carbon monoxide concentrations in parts per billion at the level in the atmosphere where the pressure is 500 millibars about 4,000 metres, from March 1st 2000 through to December 31st 2000. Concentration ranges from zero purple to around 300ppb red. Carbon monoxide is a poisonous gas released by combustion, notably in vehicle exhaust. Levels are clearly higher in the more densely_populated Northern Hemisphere. The measurements were made using MOPITT, the Measurements of Pollution in the Troposphere, an instrument on NASA磗 Terra satellite.