In order to determine the factors driving the imbalance, the investigators examined changes in clouds, water vapor, trace gases, the output of light from the Sun, Earth’s surface albedo (the amount of light reflected by the surface), atmospheric aerosols, and changes in surface and atmospheric temperature distributions. Earth’s energy imbalance is the net effect of all these factors. The warming drives other changes, such as the melting of snow and ice, increased water vapor, and cloud changes that can further enhance the warming. Increases in emissions of greenhouse gases such as carbon dioxide and methane trap heat in the atmosphere, capturing outgoing radiation that would otherwise escape into space. The magnitude of the increase is unprecedented.” “And over this period they’re both causing warming, which leads to a fairly large change in Earth’s energy imbalance. “It’s likely a mix of anthropogenic forcing and internal variability,” said Loeb. “The trends we found were quite alarming in a sense.”įor two decades, CERES instruments have measured longwave radiation emitted by Earth. “The two very independent ways of looking at changes in Earth’s energy imbalance are in really, really good agreement, and they’re both showing this very large trend, which gives us a lot of confidence that what we’re seeing is a real phenomenon and not just an instrumental artifact,” said Norman Loeb, lead author for the study and principal investigator for CERES at NASA’s Langley Research Center. Since approximately 90 percent of the excess energy from an energy imbalance ends up in the ocean, the overall trends of incoming and outgoing radiation should broadly agree with changes in ocean heat content. A global array of ocean floats, called Argo, provide data to enable an accurate estimate of the rate at which the world’s oceans are warming. NASA’s Clouds and the Earth’s Radiant Energy System (CERES) satellite sensors measure how much energy enters and leaves Earth’s system. Scientists at NASA and the National Oceanic and Atmospheric Administration compared data from two independent sets of measurements. The doubling of the energy imbalance is the topic of a recent study published June 15 in Geophysical Research Letters. A positive energy imbalance means the Earth system is gaining energy, causing the planet to heat up. Earth’s climate is determined by a delicate balance between how much of the Sun’s radiative energy is absorbed in the atmosphere and at the surface and how much thermal infrared radiation Earth emits to space.
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