The Earth's climate is determined by energy transfer from the sun to the Earth's land, oceans, and atmosphere. As the Earth rotates, the sun lights up only part of the Earth at a time, and some of that incoming solar energy is reflected and some is absorbed, depending on type of area it lights. The average amount of reflection and absorption is critical to the climate, because the absorbed energy heats up the Earth until it is radiated away as thermal radiation. This animation shows the monthly average clear-sky albedo from July, 2002 through June, 2004 as measured by the CERES instrument. This is the fraction of the incoming solar radiation that is reflected back into space by regions of the Earth on cloud-free days. The regions of highest albedo are regions of snow and ice, followed by desert regions. Oceans have the lowest albedo, and reflect very little of the incoming solar radiation. It is not possible to measure the albedo during the winter months at the poles, since there is no incoming solar radiation during these times.
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