Observing & Predicting

Uncommon atmospheric circumstances spawned a pair of tropical cyclones in the western Pacific—one on either side the equator, at nearly the same longitude, at nearly the same time. Why are twin cyclones more common during El Niño?

Tuesday, September 1, 2009

  •  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.