![]() One of the most compelling parts of the global map is the signature of the El Niño–Southern Oscillation (ENSO) pattern in the Pacific Ocean (right and left ends of the global map). At the same time, Antarctic sea ice there has been increasing slightly each year. Around the South Pole, reflectivity is down around West Antarctica and up slightly in parts of East Antarctica, but there is no net gain or loss. At the North Pole, reflectivity decreased markedly, a result of the declining sea ice on the Arctic Ocean and increasing dust and soot on top of the ice. In the maps at the top of the page, however, some regional patterns emerge. As noted in the anomaly plot below, global albedo rose and fell in different years, but did not necessarily head in either direction for long. Taken across the planet, no significant global trend appears. Shades of blue mark areas that reflected more sunlight over time (increasing albedo), and orange areas denote less reflection (lower albedo). This global picture of reflectivity (also called albedo) appears to be a muddle, with different areas reflecting more or less sunlight over the 12-year record. The maps above show how the reflectivity of Earth-the amount of sunlight reflected back into space-changed between March 1, 2000, and December 31, 2011. Using satellite measurements accumulated since the late 1970s, scientists estimate Earth’s average albedo is about about 0.30. ![]() ![]() Changes in ice cover, cloudiness, airborne pollution, or land cover (from forest to farmland, for instance) all have subtle effects on global albedo. ![]() On the other hand, if Earth was covered by a dark green forest canopy, the albedo would be about 0.14 (most of the sunlight would get absorbed). If Earth was completely covered in ice, its albedo would be about 0.84, meaning it would reflect most (84 percent) of the sunlight that hit it. The last remaining CERES instrument will fly on the JPSS-1 satellite, and a follow-on, the Radiation Budget Instrument (RBI), will fly on JPSS-2. The first CERES went into space in 1997 on the Tropical Rainfall Measuring Mission, and three more have gone up on Terra, Aqua, and Suomi-NPP. The instruments use scanning radiometers to measure both the shortwave solar energy reflected by the planet (albedo) and the longwave thermal energy emitted by it. Is more energy being absorbed by Earth than is being lost to space? If so, what happens to the excess energy?įor seventeen years, scientists have been examining this balance sheet with a series of space-based sensors known as Clouds and the Earth’s Radiant Energy System, or CERES. Exactly how much sunlight is absorbed depends on the reflectivity of the atmosphere and the surface.Īs scientists work to understand why global temperatures are rising and how carbon dioxide and other greenhouse gases are changing the climate system, they have been auditing Earth’s energy budget. About one-third of that energy is reflected back into space, and the remaining 240 watts per square meter is absorbed by land, ocean, and atmosphere. Averaged over the entire planet, roughly 340 watts per square meter of energy from the Sun reach Earth. Sunlight is the primary driver of Earth’s climate and weather. ![]()
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