Where do global temperature data come from?
Modern observations mostly come from weather stations, weather balloons, radars, ships and buoys, and satellites. A surprisingly large number of U.S. measurements are still made by volunteer weather watchers. There are more than 8,700 citizen observers in the National Weather Service's Cooperative Observer Program, who log daily weather data. On the ocean, moored and drifting buoys have begun to replace ships in recent decades as the primary method for measuring temperatures at sea.
The U.S. organization responsible for preserving the global climate record is the National Climatic Data Center (NCDC) of the National Oceanographic and Atmospheric Administration (NOAA). Other nations also maintain archives of global weather and climate observations.