Total Solar Irradiance Data in Climate Studies
Most of the energy emanating from the sun to the Earth is primarily transmitted in the optical wavelengths of visible (~85%), ultraviolet (~10%), and infrared (~5%) energy. Climate modelers want to know how much of this energy reaches the Earth, so it is necessary to make two primary measurements. The first measurement is the total irradiance delivered by the sun to the Earth. This is the measurement ACRIM makes that include the ultraviolet, visible, and near-infrared wavelengths. The second measurement is to determine how much of the sunlight is reflected back into space so that it does not become part of the Earth’s energy system. These observations are made by another series of NASA satellites as part of the Earth Radiation Budget Experiments. Subtracting the amount of reflected light from the total delivered results in the amount of energy that becomes part of the Earth system. It is this energy that creates the winds, heats the land, and helps to drive the ocean currents. Climate scientists take the total input energy along with complementary measurements of ocean currents, winds, and surface temperatures and make models that they hope will predict the climate behavior of the Earth in the future.
Related Data Sets
left: Net radiation absorbed or emitted by the Earth, measured by the Earth Radiation Budget Experiment (ERBE.) ERBE’s descendent—Clouds and the Earth’s Radiant Energy System (CERES) measures the energy captured by the Earth, while ACRIM measures the total energy emitted by the sun. (Image courtesy Dennis Hartmann, University of Washington)