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Scientists are using data from the CERES instruments to study the balance between the energy that the Earth receives from the Sun and the energy that the Earth loses to space. The CERES instrument can directly measure the amount of heat energy that any region on the Earth is emitting to space, but CERES cannot directly measure the amount of solar energy that is absorbed by the Earth. Instead, CERES can only measure the brightness (or albedo) of the region. The brightness tells us how much of the Sun's energy is reflected by the Earth. Clear regions are not very bright. Cloudy and snow-covered regions are the brightest.
Once CERES has measured a region's brightness, we can calculate the energy absorbed by the Earth and its atmosphere only if we know how much energy is arriving at the region from the Sun. The absorbed energy is equal to the difference between the total energy and the reflected energy.
Fortunately we can very accurately calculate the total solar energy if we know the Sun's elevation angle. When this angle is large (sun high in the sky) the Earth receives more energy. When this angle is small (sun closer to horizon) the Earth receives less energy.
You have certainly experienced this effect yourself. The Sun is highest in the sky in the summer and near noon. At this time, the Earth absorbs a great amount of energy and heats up quickly. On the other hand, when the Sun begins to set, the Earth cools down as less energy is received from the Sun.
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