The three main trace gases, carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (NO₂), are also known as greenhouse gases. Greenhouse gases are mostly "transparent" to incoming solar radiation; that is, they rarely interact with sunlight. However, these gases are very efficient at trapping heat radiated from the Earth's surface by absorbing and re-emitting it (the Greenhouse effect) which makes them prime candidates for study by IR radiometers and vertical sounders flown on weather satellites.

Water vapor is the most abundant greenhouse gas and the main reason our atmosphere is warm enough to support life. Of the other three main greenhouse gases, carbon dioxide is the most abundant. However, nitrous oxide is 270 times more capable of absorbing heat than carbon dioxide and methane is 21 times more efficient at this process, which is why all three are being monitored closely by scientists via satellite technology and other research tools.

Below are two images derived from satellite sounders, the first depicts carbon dioxide in the upper atmosphere and the second image illustrates an ozone feature in the Great Lakes Region during July 2003.

GOES Sounder sensing CO2 in the upper troposphere (shortwave absorbtion region)