domingo, 29 de enero de 2012

Earth Science - Earth’s “Missing Energy”

Clouds play a vital role in Earth's energy balance, cooling or warming Earth's surface depending on their type. This painting, "Cumulus Congestus," by JPL's Graeme Stephens, principal investigator of NASA's CloudSat mission, depicts cumulus clouds, which transport energy away from Earth's surface. Image credit: Graeme Stephens
Like many of us, Earth works on a budget – an energy budget. However, this energy isn’t the type that powers our automobiles or electric lights. It’s the energy that empowers our living planet. When it comes to input and output, the Earth is a huge throughput system. The most massive source of incoming energy is solar radiation, with geothermal and tidal energy completing the circle. All of these forms of energy are converted to heat and re-radiated into space. In 2010, scientists at the National Center for Atmospheric Research in Boulder, Colorado publicized a study taken from satellite observations which stated there were certain variances between Earth’s heat and ocean heating. What they found was “missing energy” in our planet’s system. Why did this energy seem to be disappearing? The research group began wondering if perhaps there was a problem with the method of recording energy as absorbed from the Sun and its emission back to space.
This was a question that needed an answer. Enter an international team of atmospheric scientists and oceanographers, led by Norman Loeb of NASA’s Langley Research Center in Hampton, Virginia, and including Graeme Stephens of NASA’s Jet Propulsion Laboratory in Pasadena, California. It was their mission to account for the missing energy. Armed with 10 years of data from NASA Langley’s orbiting Clouds and the Earth’s Radiant Energy System Experiment (CERES) instruments, the team set out to record the radiation balance located at the apex of Earth’s atmosphere and how it changed with time. Supplied with the CERES data, they then combined it with estimates of oceanic heat content as recorded by three separate sensors. Their findings showed that both satellite and physical measurements of the ocean’s energy agreed with one another once observational uncertainties were added to the equation. Their work was summarized in a NASA-led study published January 22 in the journal Nature Geosciences,
“One of the things we wanted to do was a more rigorous analysis of the uncertainties. When we did that, we found the conclusion of missing energy in the system isn’t really supported by the data.” said Loeb. “Our data shows that Earth has been accumulating heat in the ocean at a rate of half a watt per square meter (10.8 square feet), with no sign of a decline. This extra energy will eventually find its way back into the atmosphere and increase temperatures on Earth.”
For the most part, scientists concur that around 90% of extra heat created by the greenhouse gas effect is being stored in Earth’s oceans. If it follows the laws of thermodynamics and is released back into the atmosphere, “a half-watt per square meter accumulation of heat could increase global temperatures by 0.3 or more degrees centigrade or 0.54 degree Fahrenheit”. As Loeb explained, these observations show the need to employ several different measuring systems over time and the findings underline the imperative need to continually update how Earth’s energy flows are recorded.
The newly published work came from the science team at the National Center for Atmospheric Research and other authors of the paper are from the University of Hawaii, the Pacific Marine Environmental Laboratory in Seattle, the University of Reading United Kingdom and the University of Miami. Their study mapped inconsistencies between satellite information on Earth’s heat balance between the years of 2004 and 2009 and included information on the rate of oceanic heating taken from the upper 700 meters of the surface. They said the inconsistencies were evidence of “missing energy.”
Original Story Source: JPL News Release.
Source: Universe Today

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