Does a Weaker Sun Mean a Warmer Earth?


SOLAR SURPRISE: In the most recent solar cycle, the sun put out more visible light than anticipated by scientists, exacerbating global warming

SOLAR SURPRISE: In the most recent solar cycle, the sun put out more visible light than anticipated by scientists, exacerbating global warming. Image: Courtesy of NASA / Solar Dynamics Observatory

Changes in the sun’s output of various wavelengths of light have been warming the planet recently, contradicting scientists’ computer models of the solar cycle

The sun controls Earth’s climate, bathing us in light ranging from ultraviolet to visible that warms the planet and drives the heat engines we know as weather systems and ocean currents. The sun is changeable, cycling from maximum to minimum outputs over a roughly 11-year cycle, increasing or decreasing the amount of light that reaches Earth as a result of the poorly understood aspects of the sun’s seething nuclear fusion. Now new satellite measurements reveal that from 2004 to 2007—the declining phase of an unusually low and prolonged solar minimum—the sun put out even less ultraviolet light than expected but compensated by putting out more visible light.

“The amount of visible radiation entering the lower atmosphere was increasing, which implies warming at the surface,” says atmospheric physicist Joanna Haigh of Imperial College London, who led the research, published in Nature on October 7. (Scientific American is part of Nature Publishing Group.) “The solar radiative forcing of climate increased by 0.1 [watt per square meter].” That means the sun, at least for those three years, played a larger role in ongoing climate change than previously thought.

More (click here) David Bielo, Scientific American, 2010-10-07

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