U.S. Department of Energy

    Studies Find More Solar Energy Reaching Earth's Surface

    May 11, 2005

    It's bad news for the planet, but it could be good news for solar power: more solar energy is now reaching the surface of the Earth. Although a report in the late 1980s showed a 4 to 6 percent decline in sunlight between then and 1960, a new report indicates that the amount of sunlight has increased about 4 percent in the last 10 years. The report, co-authored by a scientist from DOE's Pacific Northwest National Laboratory (PNNL), does not attribute a cause to the dimming and brightening, although it lists aerosols—liquids and solids suspended in the air—and their effects on cloud formation as possible explanations. According to PNNL, the brightening effect may accelerate warming at the surface and unmask the full effect of greenhouse warming. The report is one of two papers on the subject that were printed in the May 6th issue of Science magazine, neither of which speculated on the potential effects on solar power production. See the PNNL press release.

    The PNNL news fits well with a recent study by NASA's Goddard Institute of Space Studies (GISS), which found that Earth is currently absorbing more energy than it is radiating out to space: about 0.85 Watts of energy per square meter, to be exact. The NASA scientists used global climate models, ground-based measurements, and satellite observations to measure the Earth's energy balance, and concluded that the oceans are absorbing much of the excess energy. The authors conclude that since a large amount of this excess energy is "hiding" in Earth's oceans, its full effect on the climate system is still unrealized. See the GISS press release.