Section 3
Section 5
Sources of climate data
Present Day
Climate observations are collected by a diverse suite of networks, including data from satellites in regular orbits, from aircrafts, from ground-based stations scattered around the globe, and from ships or autonomous drifting floats moving around the global oceans. There are millions of weather observations occurring within a day. These diverse streams of data are synthesized in data assimilation models, which are weather and climate models that merge the incomplete observations and the model forecasts to produce continuous maps of the desired variables.

Climate Observations at NOAA. NOAA's National Climatic Data Center has approximately 1200 stations on land and ocean, which provide daily values for many variables including pressure, vapor pressure, mean temperature, and total precipitation. Also, over 3,000 free-drifting "Argo" floats measure temperature and salinity of the upper 2,000 meters of the ocean and relay this information via satellite to various data centers.


Climate models use a variety of historical data records for model development and validation. Information on atmospheric and oceanic temperature and chemistry can be found in ice cores, sea floor sediments, tree rings, and corals. Air bubbles trapped in ice cores provide information about air chemistry at the time of ice formation. The isotopic composition of oxygen within the air bubbles provides information about historic air temperature. In ocean sediments, the shells of foraminifera, a small marine organism, can be analyzed chemically to learn about the chemistry of the seawater when the shell was deposited on the seafloor. The relative abundance of shells of different types of foraminifera also provides insights into the temperature of the water. Historical records of sea ice, vegetation, response to volcanic eruptions, clouds, and snowpack, as well as standard measurements such as temperature and rainfall, are all needed to validate climate models.