A new NASA study underscores the fact that greenhouse gases generated by human activity — not changes in solar activity — are the primary force driving global warming.
The study offers an updated calculation of the Earth’s energy imbalance, the difference between the amount of solar energy absorbed by Earth’s surface and the amount returned to space as heat. The researchers’ calculations show that, despite unusually low solar activity between 2005 and 2010, the planet continued to absorb more energy than it returned to space.
A graph of the sun’s total solar irradiance shows that in recent years irradiance dipped to the lowest levels recorded during the satellite era. The resulting reduction in the amount of solar energy available to affect Earth’s climate was about .25 Watts per square meter, less than half of Earth’s total energy imbalance. (Credit: NASA/James Hansen)
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