NASA Report: Greenhouse Gases, Not Sun, Driving Warming
Wynne Parry, LiveScience Senior WriterDate: 02 February 2012 Time: 10:59 AM ET
The sun's activity recently picked up, as shown here in this image of a massive eruption on its surface on Jan. 23. As part of its 11-year cycle, the sun is now ramping up, after an unusually long lull.

A recent, prolonged lull in the sun's activity did not prevent the Earth from absorbing more solar energy than it let escape back into space, a NASA analysis of the Earth's recent energy budget indicates.

An imbalance like this drives global warming � since more energy is coming in than leaving � and, because it occurred during a period when the sun was emitting comparatively low levels of energy, the imbalance has implications for the cause of global warming.

The results confirm greenhouse gases produced by human activities are the most important driver of global climate change, according to the researchers.

They found that the Earth absorbed 0.58 watts of excess energy per square meter than escaped back into space during the study period from 2005 to 2010, a time when solar activity was low. By comparison, the planet receives 0.25 watts less energy per square meter during a solar minimum, than during a period of maximum activity in the sun's 11-year cycle. (Currently, the sun is in the midst of Solar Cycle 24, with activity expected to ramp up toward solar maximum in 2013.)