“SINCE 1979, NOAA satellites have been carrying instruments which measure the natural microwave thermal emissions from oxygen in the atmosphere. The signals that these microwave radiometers measure at different microwave frequencies are directly proportional to the temperature of different, deep layers of the atmosphere.
“Every month, John Christy and I update global temperature datasets that represent the piecing together of the temperature data from a total of eleven instruments flying on eleven different satellites over the years. As of 2008, our most stable instrument for this monitoring is the Advanced Microwave Sounding Unit (AMSU-A) flying on NASA’s Aqua satellite.
“The graph above represents the latest update; updates are usually made within the first week of every month.”
July 3, 2009
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