Meteorologists have known for years that the pattern of the polar vortex determines how much cold air escapes from the Arctic and makes its way to the U.S. during the winter. Climate scientists are wondering if a warmer Arctic could explain its odd behavior in recent years.

 The Sun is the main source of power for the Earth's climate machine. Space-based measurements, begun in 1978, indicate Earth receives an average of 1,361 W/m<sup>2</sup> of incoming sunlight, and the amount varies by about one-tenth of a percent over the course of the 11-year solar cycle. 

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